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Objective To evaluate the efficacy and safety of fruquintinib alone or in combination with immune checkpoint inhibitor (ICI) in patients with microsatellite stable (MSS) metastatic colorectal cancer (mCRC)in third⁃line or above treatment. Methods Patients with pMMR/MSS type mCRC admitted to the Department of Oncology, Renmin Hospital of Wuhan University, from January 2020 to April 2024 were selected as the research objects. The prognoses, efficacies and safeties of fruquintinib alone and in combination with ICI were compared in the unadjusted model and the propensity score matching. Results A total of 104 patients were included in the analysis, 33 in the fruquintinib group and 71 in the fruquintinib combined with ICI group. Compared to the fruquintinib group, the median progression⁃free survival was longer in the fruquintinib combined ICI group (3.0 months vs 4.5 months; HR=0.55, 95%CI: 0.33-0.89）. However, there were no significant differences in the median overall survival (10.1 months vs 13.1 months）, the objective response rate (9.1% vs 11.3%) and the disease control rate (51.5% vs 66.2%)between the two groups (all P>0. 05）. Similar results were obtained in the analysis of the propensity score matching. The adverse events of grade 3 or above in both groups mainly included hand⁃foot⁃skin reaction, thrombocytopeniaandleukopenia. The incidence of grade 3 or above adverse events was 30. 3% in the fruquintinib group and 36.6% in the fruquintinib combined with ICI group (P=0.529）. Conclusions Compared with fruquintinib, fruquintinib combined with ICI provides benefits in the progression ⁃free survival for pMMR/MSS type mCRC patients in third ⁃line or above treatment with controllable safety, which is worthy of further study. [ABSTRACT FROM AUTHOR]

Background: Programmed cell death receptor 1 (PD-1) and programmed cell death ligand 1 (PD-L1) are important immune checkpoint molecules that contribute to tumor immune evasion. However, the main treatment modalities for patients with early and intermediate stage colorectal cancer (CRC) are surgery, and the role of PD-1/PD-L1 inhibitors in these patients is not yet clear. Therefore, this study aims to review the treatment progress of PD-1/PD-L1 inhibitors for early- and intermediate-stage microsatellite high-instability (MSI-H) and stable (MSS) colorectal cancer, in order to provide more options for patients with early- and intermediate-stage colorectal cancer. Materials and methods: A scoping review of clinical trial registries (Clinicaltrials.gov and EU clinical trial registers) and PubMed/Medline database of trials on PD-1/PD-L1 Inhibitors for early and middle-stage MSI-H and MSS CRC was done up to March 2024. Results: A total of 19 trials related to early to mid-stage MSH-I or MSS CRC were included. Among them, 6 trials are in recruiting status, 3 trials are in active, not recruiting status, 3 trials are completed, 1 trial is terminated, and 1 trial is unknown. Of these, 9 trials involve MSI-H type CRC, and 10 trials involve MSS type CRC. Preclinical phase I/II trials are predominant, with only 3 clinical phase III trials. In trials related to MSI-H type CRC, 4 studies involve PD-1/PD-L1 inhibitors combined with neoadjuvant therapy, and 5 studies involve combination therapy. In trials related to MSS type CRC, 3 studies involve PD-1/PD-L1 inhibitors combined with targeted therapy, 2 studies involve PD-1/PD-L1 inhibitors combined with chemotherapy, 1 study involves PD-1/PD-L1 inhibitor combined immunotherapy, 1 study involves PD-1/PD-L1 inhibitors combined with bacterial therapy, and 3 studies involve PD-1/PD-L1 inhibitors combined with comprehensive therapy. As for primary outcome measures, 4 trials select pathological complete response rates, 3 trials select progression-free survival rate, 3 trials select objective response rate, 3 trials select overall survival rate, 4 trials select disease-free survival rate, 1 trial selects clinical complete response rate, and 1 trial selects percentage of participants with a dose-limiting toxicity. Conclusion: For early- and middle-stage MSI-H and MSS CRC, PD-1/PD-L1 inhibitors have shown some therapeutic efficacy, as evidenced by phase I/II studies. However, contemporary trial designs exhibit heterogeneity, with relatively few inclusion criteria, the use of various drug combinations and regimens, and significant variations in reported endpoints. Nevertheless, more double-arm, multicenter, randomized controlled trials are still needed to confirm the efficacy of immunotherapy. [ABSTRACT FROM AUTHOR]

Immunotherapy based on the PD-1/PD-L1 axis blockade has no benefit for patients diagnosed with colon cancer liver metastasis (CCLM) for the microsatellite stable/proficient mismatch repair (MSS/pMMR)) subtype, which is known as an immune-desert cancer featuring poor immunogenicity and insufficient CD8+ T cell infiltration in the tumor microenvironment. Here, a multifunctional nanodrug carrying a cyclin-dependent kinase (CDK)1/2/5/9 inhibitor and PD-L1 antibody is prepared to boost the immune checkpoint blockade (ICB)-based immunotherapy against MSS/pMMR CCLM via reversing the immunosuppressive tumor microenvironment. To enhance the MSS/pMMR CCLM-targeting efficacy, we modify the nanodrug with PD-L1 knockout cell membrane of this colon cancer subtype. First, CDKs inhibitor delivered by nanodrug down-regulates phosphorylated retinoblastoma and phosphorylated RNA polymerase II and meanwhile arrests the G2/M cell cycle in CCLM to promote immunogenic signal release, stimulate dendritic cell maturation, and enhance CD8+ T cell infiltration. Moreover, CDKi suppresses the secretion of immunosuppressive cytokines in tumor-associated myeloid cells sensitizing ICB therapy in CCLM. Notably, the great efficacy to activate immune responses is demonstrated in the patient-derived xenograft model and the patient-derived organoid model as well, revealing a clinical application potential. Overall, our study represents a promising therapeutic approach for targeting liver metastasis, remolding the tumor immune microenvironment (TIME), and enhancing the response of MSS/pMMR CCLM to boost ICB immunotherapy. Schematic illustration of preparation and CCLM-targeted therapy of engineered cell membrane-camouflaged nanodrug. (A) Preparation of engineered cell membrane-camouflaged nanoparticles co-delivered with CDK inhibitor (CDKi) and anti-mouse/human programmed death ligand 1 antibody (aPD-L1) in response to extracellular acidity of tumor microenvironment. (B) Multifunctional nanodrug targets CDKs in colon cancer cell and tumor-associated myeloid cell (TAMC) to activate aPD-L1 immunotherapy against liver metastasis of immune-desert colon cancer. [Display omitted] [ABSTRACT FROM AUTHOR]

Purpose: Several studies have demonstrated the effectiveness of anti-angiogenic drugs in combination with immune checkpoint inhibitors (ICIs) in patients with microsatellite stable (MSS) or mismatch repair proficient (pMMR) metastatic colorectal cancer (mCRC). However, whether combination radiotherapy (RT) can further improve the prognosis of mCRC patients after second-line treatment remains to be explored. Methods: Retrospective analysis of data from mCRC patients who received antiangiogenic targeted therapy (TT) and immunotherapy (IT) with or without RT after the failure of standard therapy. Progression-free survival (PFS), overall survival (OS), objective response rate (ORR), disease control rate (DCR), and safety were evaluated. Results: A total of 82 patients who received TT + IT were analyzed. For RT group (n = 42) versus NRT group (n = 40), ORR was 21.4% (9/42) versus 5.0% (2/40); DCR was 83.8% (35/42) versus 65.0% (26/40). Compared with NRT group, RT improved PFS (median: 5.0 vs. 3.6 months; p = 0.04) and OS (median: 15.2 vs. 7.2 months; p = 0.01). In addition, in the population receiving RT, the PFS of RT sequential/simultaneous TT + IT was superior to TT + IT sequential RT (median: 7.1 vs. 6.2 vs. 3.5 months, p = 0.004). Multivariate analysis suggested RT was an independent prognostic factor for PFS and OS. No treatment-related deaths were reported.Conclusions: Compared with TT + IT, RT combined with TT + IT improved survival outcomes in MSS/pMMR mCRC patients, with manageable toxicity. RT sequential/simultaneous TT + IT treatment is expected to be the optimal strategy for MSS/PMMR mCRC. [ABSTRACT FROM AUTHOR]

Objective To investigate the clinical efficacy and safety of fruquintinib combined with sintilimab in the treatment of advanced microsatellite stable (MSS) colorectal cancer. Methods A retrospective study of 44 patients with MSS colorectal cancer treated with fruquintinib and sintilimab was conducted. The patients were divided into the fruquintinib alone (n=22) and fruquintinib combined with sintilimab (n=22) groups. The treatment regimen was as follows: The patients in the fruquintinib alone group consumed oral fruquintinib capsules at 5 mg/d once for three consecutive weeks with a one week stop in 28 day cycles. The patients in the fruquintinib combined sintilimab group were injected intravenously with sintilimab (200 mg) once per three weeks, and fruquintinib was used in the same manner as the fruquintinib alone group. Results The objective response rate (ORR) of the fruquintinib alone group was 9.09%, the disease control rate (DCR) of the fruquintinib alone group was 45.45%. The ORR of the fruquintinib combined with sintilimab group was 18.18%, and the DCR was 63.64%. The median PFS of the fruquintinib alone and fruquintinib combined with sintilimab groups were 4.4 months (IQR: 2.1-8.2) and 6.7 months (IQR: 3.9-12.6), respectively (χ2 =4.372, P=0.037). Most of the adverse reactions during the treatment of the two groups were grades 1-2. In addition, no significant difference in the incidence of adverse reactions was found between two groups (P>0.05). Conclusion Compared with fruquintinib alone, fruquintinib combined with sintilimab in the treatment of patients with MSS colorectal cancer after the failure of standard treatment has better clinical efficacy, and adverse drug reactions can be controlled． [ABSTRACT FROM AUTHOR]

Background: Although the use of regorafenib plus nivolumab demonstrates promising outcomes in patients with refractory microsatellite stable (MSS) metastatic colorectal cancer (mCRC), this effect has not been substantiated in other studies. Moreover, a comparison between the outcomes of regorafenib and programmed cell death protein 1 (PD‐1) antibody combination therapy and regorafenib monotherapy remains unexplored. In this study, we aimed to assess whether regorafenib and PD‐1 antibody combination therapy is superior to regorafenib monotherapy as a third‐line treatment for MSS mCRC. Methods: Patients with MSS mCRC who received regorafenib and PD‐1 antibody or regorafenib monotherapy as third‐line treatment were eligible for inclusion. Results: In total, 179 patients were enrolled, of which 84 were administered regorafenib combined with a PD‐1 antibody and 95 were administered regorafenib monotherapy. Patients administered regorafenib combined with a PD‐1 antibody had similar progression‐free survival (PFS) as those on regorafenib monotherapy (median PFS was 2.4 months and 1.9 months, respectively, p = 0.086). The administration of regorafenib combined with a PD‐1 antibody resulted in significantly longer PFS than that seen with regorafenib monotherapy in both male (5.2 months vs. 2.4 months, p = 0.001) and female (3.9 months vs. 1.8 months, p = 0.037) patients without liver metastasis. Female patients with liver metastasis who were administered regorafenib combined with a PD‐1 antibody had shorter PFS than those administered regorafenib monotherapy (1.8 months vs. 2.0 months, p = 0.030). Conclusion: Liver metastasis and sex are predictors of survival benefit following the addition of a PD‐1 antibody to regorafenib in patients with MSS mCRC. [ABSTRACT FROM AUTHOR]

Objective: Immune checkpoint inhibitors have been widely used in the treatment of endometrial cancer (EC) with microsatellite instability-hypermutated (MSI-H). However, there is an unmet need for microsatellite stable (MSS) EC because of their modest activity. This study aimed to identify potential immune-related biomarkers in MSS EC. Methods: One hundred and twenty-three patients with EC who underwent hysterectomy were enrolled. MSI status was determined using MSI analysis and/or immunohistochemical staining for mismatch repair proteins. Immunohistochemical analysis of programmed cell death protein 1 (PD-1), programmed death-ligand 1 (PD-L1), PD-L2, cytotoxic T-lymphocyteassociated protein 4 (CTLA-4), cluster of differentiation 3 (CD3), CD8, lymphocyte activation gene-3 (LAG-3), indoleamine 2,3-dioxygenase 1 (IDO1), phosphatase and tensin homolog (PTEN), p53, AT-rich interactive domain-containing protein 1A (ARID1A), and ß-catenin was performed using tissue microarray blocks. Results: Among 123 patients, 95 (77.2%) were classified as having MSS. Within EC with MSS, PD-L1 positivity was significantly associated with positive PD-1 (p<0.001), CTLA-4 (p<0.001), CD3 (p=0.002), CD8 (p<0.001), and LAG-3 (p<0.001). In the univariate analysis, positive PD-1 (odds ratio [OR]=9.281; 95% confidence interval [CI]=2.560-33.653; p<0.001), CTLA-4 (OR=5.33; 95% CI=1.418-19.307; p=0.005), CD3 (OR=5.571; 95% CI=1.746-17.775; p=0.004), CD8 (OR=6.909; 95% CI=2.647-18.037; p<0.001), and LAG-3 (OR=9.75; 95% CI=1.947-48.828; p=0.005) were significantly associated with PD-L1 positivity in MSS EC. In the multivariate analysis, LAG-3 demonstrated a significant association with positive PD-L1 expression in MSS EC (OR=5.061; 95% CI=1.534-16.693; p=0.023). Conclusion: In patients with MSS EC harboring PD-L1, LAG-3 may be a potential immunotherapeutic target. Clinical trials investigating the role of anti-LAG-3 antibodies, alone or in combination with other immunotherapies, are warranted. [ABSTRACT FROM AUTHOR]

Combination regorafenib, ipilimumab, and nivolumab (RIN) was evaluated in a phase 1 nonrandomized study (NCT04362839) of refractory microsatellite stable (MSS) metastatic colorectal cancer. Promising antitumor activity was previously reported in the non-liver metastatic (NLM) population. This updated analysis describes long-term survival outcomes in the NLM cohort and highlights durable remissions with potential cure following completion of RIN therapy. Between May 2020 and January 2022, 39 patients with refractory MSS metastatic colorectal cancer were enrolled. Patients received RIN until progression, unacceptable toxicity, or completion at two years. The primary endpoint was recommended phase 2 dose (RP2D) selection. Secondary endpoints were safety, overall response rate (ORR), progression-free survival (PFS) and overall survival (OS) at the RP2D level. 22 patients with refractory non-liver metastatic MSS colorectal cancer were treated at the RP2D of RIN. ORR was 36.4 % (8/22 patients), and median PFS was 5.0 months (95 % CI: 3–9). After a median follow-up of 42 months, the 1-, 2-, and 3-year PFS rates were 24.1 %, 24.1 %, and 19.3 % by RECIST. The median OS was 27.5 months (95 % CI: 14.0 to NE). At data cutoff, 6 patients had ongoing clinical benefit, including 3 responders who remain disease-free > 18 months after treatment completion. With extended follow-up, RIN combination therapy demonstrated durable clinical benefit in a subset of patients with NLM MSS metastatic colorectal cancer, including potential cure in 3 responders who remain disease-free > 18 months after treatment completion. • Regorafenib, ipilimumab, and nivolumab was potentially curative in microsatellite stable tumors. • Long-term efficacy was observed only in the non-liver metastatic colorectal cancer cohort. • 3-year progression-free survival was 19.3 %. • 3-year overall survival was 40.9 %. • 3 responders remain disease-free for > 18 months after completing RIN therapy. [ABSTRACT FROM AUTHOR]

The exploration of biomarkers predicting response to immune checkpoint inhibitors in microsatellite stability colorectal cancer can enable more patients to benefit from immunotherapy. Tumor mutational burden (TMB), POLE/POLD1 mutation, CMS classifications, MGMT methylation, and other indicators own the potential and value of predicting response to immune checkpoint inhibitors in microsatellite stability colorectal cancer. In this paper, we reviewed the related research on predictive biomarkers of immune checkpoint inhibitors in microsatellite stability colorectal cancer, provide a reference for the best treatment strategy for microsatellite stability colorectal cancer. [ABSTRACT FROM AUTHOR]

Introduction: A large proportion of indigenous African (IA) colorectal cancer (CRC) patients in South Africa are young (< 50 years), with no unique histopathological or molecular characteristics. Anatomical site as well as microsatellite instability (MSI) status have shown to be associated with different clinicopathological and molecular features. This study aimed to ascertain key histopathological features in microsatellite stable (MSS) and low-frequency MSI (MSI-L) patients, to provide insight into the mechanism of the disease.Methods: A retrospective cohort (2011-2015) of MSS/MSI-L CRC patient samples diagnosed at Charlotte Maxeke Johannesburg Academic Hospital was analyzed. Samples were categorized by site [right colon cancer (RCC) versus left (LCC)], ethnicity [IA versus other ethnic groups (OEG)] and MSI status (MSI-L vs MSS). T-test, Fischer's exact and Chi-square tests were conducted.Results: IA patients with LCC demonstrated an increased prevalence in males, sigmoid colon, signet-ring-cell morphology, MSI-L with BAT25/26 marker instability and advanced disease association.Conclusion: This study revealed distinct histopathological features for LCC, and suggests BAT25 and BAT26 as negative prognostic markers in African CRC patients. Larger confirmatory studies are recommended. [ABSTRACT FROM AUTHOR]

Objective To evaluate the efficacy and safety of Regorafenib combined with PD ⁃ 1 inhibitors for the third ⁃line or above treatment of advanced microsatellite stable (MSS) colorectal cancer (CRC). Methods A total of 22 patients with advanced MSS CRC, who received Regorafenib combined with PD ⁃1 inhibitors or Regorafenib monotherapy for third ⁃line or above treatment in Renmin Hospital of Wuhan University from January 2019 to March 2022, were selected as the research objects, including 10 patients in the combination therapy group and 12 patients in the Regorafenib monotherapy group. The progression⁃free survival (PFS), overall survival (OS), objective response rate (ORR), disease control rate (DCR) and incidence of adverse events (AEs) were compared between the two groups. Results Kaplan⁃Meier survival analysis showed that there was no significant difference in median OS between the combination therapy group and the monotherapy group (6.10 months vs 6.13 months, P=0.827). However, the combination therapy group had better median PFS than the monotherapy group (4.00 months vs 1.63 months, P=0.025), and the DCR in combination therapy group were also better than the monotherapy group, though there was no statistical significance (70.0% vs 25.0%, P=0.084). No grade 4 or higher AEs were observed in either group. The overall incidence of AEs (100.0% vs 91.7%) and the incidence of grade ≥3 AEs (30.0% vs 25.0%) were not statistically different between the combination therapy group and the monotherapy group (all P>0.05). Conclusions Compared with Regorafenib monotherapy, Regorafenib combined with PD ⁃1 inhibitors as the third ⁃line or above treatment regimen for advanced MSS CRC may bring benefits for PFS, and it is worthy of further clinical trials. [ABSTRACT FROM AUTHOR]

Simple Summary: There is a crucial need to improve treatment regimens in patients with recurrent endometrial cancer. Although immunotherapy treatments have shown impressive benefit in microsatellite instability-high endometrial cancer, they have been less predictable in the majority of endometrial cancers, which are microsatellite stable. Our aim was to characterize clinical outcomes in patients with recurrent microsatellite stable endometrial cancer treated in early-phase immunotherapy clinical trials in order unravel treatment regimens that would improve response and survival. Our findings suggest that utilizing immunotherapy in combination with other non-immunotherapy agents resulted in greater duration of disease control and improved survival outcomes compared to immunotherapy only (monotherapy) or in combination with other immunotherapy agents. Future studies are needed to validate these findings. Recurrent microsatellite stable (MSS) endometrial cancer has poor response to conventional therapy and limited efficacy with immune checkpoint monotherapy. We conducted a retrospective study of recurrent MSS endometrial cancer patients enrolled in immunotherapy-based clinical trials at MD Anderson Cancer Center between 1 January 2010 and 31 December 2019. Patients were evaluated for radiologic response using RECIST 1.1 criteria, progression-free survival (PFS), and overall survival (OS). Thirty-five patients were treated with immune checkpoint inhibitors: 8 with monotherapy, 17 with immunotherapy (IO) in combination with another IO-only, and 10 with IO in combination with non-IO therapy. Among those treated with combination IO plus non-IO therapy, one had a partial response but 50% had clinical benefit. Patients who received combination IO plus non-IO therapy had improved PFS compared to those who received monotherapy (HR 0.56, 95% CI 0.33–0.97; p = 0.037) or combination IO-only therapy (HR 0.36, 95% CI 0.15–0.90; p = 0.028) and had improved OS when compared to monotherapy after adjusting for prior lines of therapy (HR 0.50, 95% CI 0.27–0.95; p = 0.036). The potential beneficial clinical outcomes of combination IO plus non-IO therapy in MSS endometrial cancer should be validated in a larger study. [ABSTRACT FROM AUTHOR]

To determine the cost-effectiveness of lenvatinib plus pembrolizumab (LP) in patients with microsatellite stable (MSS), recurrent, pretreated endometrial cancer (EC). A decision analysis model was created to evaluate the cost-effectiveness of LP relative to doxorubicin, pegylated liposomal doxorubicin (PLD), and bevacizumab in patients with recurrent pretreated MSS EC. Published data was used to estimate quality adjusted life years (QALYs) and drug cost estimates were obtained using average wholesale prices. A health state utility (HSU) penalty of −0.10 was applied to the LP group to account for treatment toxicity. Incremental cost-effectiveness ratios (ICERs) were calculated to determine cost/QALY. The willingness to pay threshold (WTP) was set at $100,000 per QALY saved. Sensitivity analyses were performed on cost, effectiveness, and HSU penalty for LP. Costs of treatment with doxorubicin, PLD, and bevacizumab are $23.7 million (M), $56.9 M, and $250.8 M respectively. Cost of treatment with LP is $1.8 billion. Relative to doxorubicin, the ICERs for PLD, bevacizumab, and LP are $56,808, $345,824, and $1.6 M respectively. A sensitivity analysis varying the cost of LP shows that if the combined drug cost decreases from over $58,000 to less than $11,000 per cycle, this strategy would be cost-effective. Eliminating the HSU penalty for LP decreased the ICER $1.0 M while increasing the penalty to −0.20 increased the ICER to $3.7 M. LP is not cost-effective in patients with recurrent pretreated, MSS EC. A dramatic reduction in cost of LP is required for this novel strategy to be cost-effective. [ABSTRACT FROM AUTHOR]

Objective: To determine the frequency of mismatch repair deficiency in colorectal carcinoma determined by immunohistochemistry. Study Design: Cross-sectional study. Place and Duration of Study: Department of Histopathology, Armed Forces Institute of Pathology, Rawalpindi, from Aug 2018 to Jan 2019. Methodology: A total of 101 patients of adenocarcinoma of colorectum who underwent surgical resections and their characteristic and clinical data were recorded. Immunohistochemical stains were performed using antibodies MLH1, MSH2, PMS2 and MSH6. Results were interpreted and mismatch repair deficiency status of all patients was determined. Patients with loss of expression for MLH1, MSH2, PMS2 and MSH6 antibodies were observed and noted. Results: In this study, out of 101 patients with CRC, 71 (70.3%) were male and 30 (29.7%) female. The mean age was (54 years ± 15.9). Amongst the 101 cases loss of immunohistochemical staining for MMR proteins was noted in 19 patients (18.8%). The combined loss of all four antibodies was seen in one case, loss of MLH1 and PMS2 in 7, MSH2 and MSH6 in 5 and MLH1 only in 6 patients. However, no mismatch repair deficiency was detected in remaining 82 cases. According to statistical analysis no significant association between mismatch repair deficiency and variables was found. Conclusion: The frequency of mismatch repair deficiency in colorectal carcinoma patients was found to be 18.8% in our population. [ABSTRACT FROM AUTHOR]

The generation of long-term durable tumor immunity and prolonged disease-free survival depends on the ability to generate and support CD8+ central memory T-cells. Microsatellite-stable colon cancer is resistant to currently available immunotherapies; thus, development of novel mechanisms to increase both lymphocyte infiltration and central memory formation are needed to improve outcomes in these patients. We have previously demonstrated that both interleukin-2 (IL-2) and LIGHT (TNFSF14) independently enhance antitumor immune responses and hypothesize that combination immunotherapy may increase the CD8+ central memory T-cell response. Murine colorectal cancer tumors were established in syngeneic mice. Tumors were treated with control, soluble, or liposomal IL-2 at established intervals. A subset of animal tumors overexpressed tumor necrosis superfamily factor LIGHT (TNFSF14). Peripheral blood, splenic, and tumor-infiltrating lymphocytes were isolated for phenotypic studies and flow cytometry. Tumors exposed to a combination of LIGHT and IL-2 experienced a decrease in tumor size compared with IL-2 alone that was not demonstrated in wild-type tumors or between other treatment groups. Combination exposure also increased splenic central memory CD8+ cells compared with IL-2 administration alone, while not increasing tumor-infiltrating lymphocytes. In the periphery, the combination enhanced levels of circulating CD8 T-cells and central memory T-cells, while also increasing circulating T-regulatory cells. Combination of IL-2, whether soluble or liposomal, with exposure to LIGHT results in increased CD8+ central memory cells in the spleen and periphery. New combination immunotherapy strategies that support both effector and memory T-cell functions are critical to enhancing durable antitumor responses and warrant further investigation. [ABSTRACT FROM AUTHOR]

Immune checkpoint inhibitors (ICIs) alone or in combination with chemotherapy (CT) are the current standard of therapy in several cancer types. Patients (pts) with lung cancer display higher response rates to CT when given after ICIs. Although ICIs have failed to demonstrate antitumour activity in microsatellite stable (MSS) metastatic colorectal cancer (mCRC), little is known about CT effect after ICIs. We aimed to assess whether sequential ICIs followed by CT may be an alternative therapeutic approach in a population of pts with mCRC. We retrospectively assessed CT after ICI (CAICI) failure in pts with mCRC. The ICI regimen consisted of anti-PD(L)1 alone or in combination. The primary end-point was objective response rate. Progression-free survival (PFS) and overall survival (OS) were secondary end-points. Between 2014 and 2018, 29 pts with mCRC received CAICI (MSS tumours, 27 pts [86%]). The median number of previous lines was 4 (range, 2–7). Regimens included TAS-102 (n = 14), FOLFIRI (irinotecan, leucovorin, and fluorouracil; n = 6) or FOLFOX (oxaliplatin, leucovorin, and fluorouracil; n = 4), regorafenib (n = 3) and carboplatin (1 pt with BRCA mutation). Partial response and stable disease were observed in 4 (19%) and 9 (43%) pts, respectively (disease control rate, 62%). The median PFS and OS were 3.8 months (95% confidence interval [CI] = 1.5–5.4) and 8.0 months (95% CI = 4.2–14.0), respectively. ICIs administered before CT might enhance cytotoxic effects even in pts with immunorefractory MSS mCRC. The results of this small cohort need to be validated in independent prospective cohorts. The role of ICIs as modifiers of both tumour cells and microenvironment in mCRC deserves further research. • Chemotherapy (CT) beyond immunotherapy was assessed in patients with metastatic colorectal cancer (mCRC). • Immunotherapy followed by CT provides tumour control in mCRC. • Immunorefractory mCRC could benefit from sequential immunotherapy and CT. • Immunotherapy-induced delayed effects might enhance chemotherapy in mCRC. [ABSTRACT FROM AUTHOR]

Programmed death 1 (PD-1)-targeted therapy has benefited patients with microsatellite instability-high metastatic colorectal cancer (mCRC). However, the efficacy of PD-1-targeted therapy is poor in patients with microsatellite-stable (MSS) mCRC. Therefore, it is imperative to explore additional co-inhibitory molecular signalling pathways to improve the efficacy of immunotherapy in MSS mCRC treatment. In the present study, the association between cyclin-dependent kinase 9 (CDK9) expression and the survival of patients with CRC was analysed using RNA sequencing data from 605 patients, including 121 cases of mortality, from human cancer datasets. Furthermore, 35 clinical MSS stage III–IV CRC specimens were collected to assess CDK9 protein expression by immunohistochemistry, and the frequency of tumor-infiltrating CD8+ T cells was assessed by flow cytometry. The human cancer datasets demonstrated that upregulation CDK9 significantly shortened the survival of patients with stage II–IV colon cancer. Additionally, CDK9 mRNA expression was positively correlated with the expression levels of genes associated with immune evasion in the tumor. Notably, CDK9 was expression was upregulated in stage IV CRC compared with para-cancerous tissues and early-stage tumors. Interestingly, CDK9 expression was negatively associated with the infiltration of CD8+ T cells at the tumor site. In addition, the expression levels of T-cell immunoglobulin mucin family member 3 and CD39, proteins associated with exhaustion, on tumor-infiltrating CD8+ T cells were significantly elevated in patients with abnormal CDK9 expression levels. The present study demonstrated that CDK9 expression was negatively associated with CD8+ T cell infiltration and positively associated with CD8+ T cell exhaustion in MSS mCRC. In conclusion, CDK9 may be utilized to evaluate the prognosis and the immune-type of the tumor microenvironment in patients with MSS mCRC. [ABSTRACT FROM AUTHOR]

A small subset of patients with proficient mismatch repair (pMMR)/microsatellite stable (MSS)-colorectal cancer (CRC) benefit from immunotherapy with anti-programmed cell death 1 (PD-1)/programmed death ligand 1 (PD-L1) blockade. Therefore, the aim of the current study was to evaluate the immune status of patients with pMMR/microsatellite instability-low (MSI-L)/MSS-CRC and deficient MMR (dMMR)/MSI-high (MSI-H)-CRC in order to identify responders to anti-PD-1/PD-L1 inhibitors. The current study used a dataset downloaded from The Cancer Genome Atlas (TCGA) as well as 219 clinical tissue samples to investigate the infiltrating grade of cluster of differentiation (CD) 4 and CD8 tumor infiltrating lymphocytes (TILs), the expression levels of PD-L1 and PD-L2, the interferon-γ (IFN-γ) and CD8 T effector gene signatures, and the phosphorylated signal transducer and activator of transcription 1 (p-STAT1) status in patients with pMMR/MSI-L/MSS-CRC and dMMR/MSI-H-CRC. Analysis of TCGA dataset revealed that the mRNA expression levels of PD-L1 and PD-L2, the IFN-γ gene signature and the CD8 T effector gene signature were significantly upregulated in MSI-H tumors compared with MSI-L/MSS tumors. Additionally, a subpopulation of patients with upregulation of the IFN-γ and CD8 T effector gene signatures was observed in those with MSI-L/MSS-CRC. Immunohistochemical staining of the clinical samples revealed a subpopulation of patients with pMMR-CRC that were positive for PD-L1 and p-STAT1, and whom had levels of elevated CD8(+) and CD4(+) TILs infiltration similar to those observed in patients with dMMR-CRC. The results obtained in the current study suggested that a subpopulation of patients with MSI-L/MSS-CRC and pMMR-CRC with upregulated IFN-γ and CD8 T effector gene signatures may benefit from immunotherapy with antibodies against PD-1 and PD-L1. [ABSTRACT FROM AUTHOR]

Background: Microsatellite instability (MSI) accounts for 15-20% of colorectal cancer (CRC) and is considered to have favorable stage-adjusted prognosis compared to Microsatellite stable (MSS) CRCs. Determination of MSI in stage II CRC is important for management decisions regarding adjuvant chemotherapy administration. The aim of this study was to determine the prognostic and predictive significance of MSI in stage 2 CRC in the Indian scenario.Materials and Methods: A total of 195 patients who underwent curative surgery for stage II CRC from 2010 to 2017 were included. MSI testing by immunohistochemistry (DNA MisMatch Repair proteins) was performed in all. Various clinicopathological factors and disease-free survival and overall survival were assessed between MSI and MSS groups. The effect of treatment in terms of survival benefits with adjuvant therapy in the MSI group was also assessed.Results: 27.1% of the CRCs' showed MSI. Younger age (<50 years), family history of cancer, synchronous/metachronous malignancies, proximal (right sided) location, poor morphological tumour differentiation, mucin production, and presence of peritumoral (Crohn's-like) lymphocytic response showed statistically significant association with MSI. Majority (56%) of our patients showed combined loss of MLH1 and PMS2. Overall, survival among the MSI patients was significantly higher (76.6 ± 4.149 months) than the MSS patients (65.05 ± 3.555)P= 0.04. MSI patients did not show any differences in survival with or without treatment.Conclusion: This study highlights the distinct clinicopathological features of MSI-related CRC and the relevance of MSI testing of stage II CRC for management decisions and prognostication. [ABSTRACT FROM AUTHOR]

About half of hereditary non-polyposis colorectal cancers (HNPCCs) fulfilling the Amsterdam criteria (AC) do not display evidence of mismatch repair defects, and the difference between microsatellite-stable (MSS) and microsatellite-unstable HNPCC remains poorly understood. The study was to compare overall copy number variation (CNV) and loss of heterozygosity (LOH) of the entire genome in HNPCCs with MSS and microsatellite-instability (MSI) using the Cytoscan HD Array. This was a study carried out in samples from 20 patients with MSS HNPCC and four patients with MSI HNPCC from the Fudan University Shanghai Cancer Center (China). The microsatellite status was examined using a panel of microsatellite markers. MMR expression status was evaluated by immunohistochemistry. Tumor samples were analyzed with the Genome-Wide Human CytoScan HD Array. CNV and LOH were determined. Fourteen specific CNVs (eight gains: 5p13.1, 7p13, 7q22.3, 8q11.21, 8q12.2, 19q13.11, 20q11.21, and 20q11.23; and six losses: 8p22, 8p23.1, 8p23.1, 17p13.1, 17p13.2, and 18q21.3) were associated with MSS HNPCC. Of these 14 CNVs, gain on 8q12.2 and loss on 17p13.1 were novel. The total length of 8q gains and 20q gains were greater in MSS tumors than in MSI ( P < 0.05). The presence of similar levels of copy-neutral-LOH in MSS (31.7%) and MSI (29.7%) HNPCC suggested that unknown DNA repair genes might be involved in the tumorigenesis of MSS HNPCC. MSS HNPCC is a genetically specific population with increased CNV, which are different from MSI HNPCC. The results may help to clarify the genetic basis of MSS HNPCC tumorigenesis. [ABSTRACT FROM AUTHOR]

Background: Microsatellite instability (MSI) is a marker of chemoresistance, but it is associated with improved survival compared with microsatellite-stable (MSS) colon cancers. We hypothesized that MSI tumors overexpress chemoresistance-associated genes and underexpress DNA damage/repair genes. We used ultra high-throughput sequencing (UHTS) to assess the expression of representative genes in MSI and MSS colon cancer cell lines. Methods: Solexa UHTS was used to examine gene expression in HCT116 (MSI) and HT29 (MSS) cells, and normal colonic mucosa (NCM). We compared expression of 40 genes involved in chemoresistance, DNA repair, DNA damage, and drug metabolism pathways. Results: We observed gene expression differences between MSI and MSS cell lines in 8 out of 40 genes involved in mismatch repair (MMR), DNA repair, drug metabolism, and chemoresistance. MMR gene expression was lower in MSI cells, which is consistent with the MSI phenotype, whereas DNA repair genes were highly expressed in these cells. Genes associated with chemoresistance and drug metabolism also had increased expression in MSI cells. No difference in expression of DNA damage genes was observed between MSI and MSS cell lines. Conclusion: Using UHTS gene expression analysis, we identified differential expression of genes between MSI and MSS cell lines which may account for resistance to chemotherapy in MSI tumors. UHTS expression analysis has the potential to identify genome-wide predictors of response or resistance to chemotherapy. [ABSTRACT FROM AUTHOR]

Circulating tumor DNA (ctDNA) is increasingly being investigated as a tool to detect minimal residual disease in resected, stage I-III colorectal cancer. Recent ctDNA studies have indicated that detection of ctDNA following surgery for resectable colorectal cancer confers a significantly higher risk of recurrence than those with negative ctDNA postoperatively. In those with postoperative ctDNA positivity, clearance of minimal residual disease with adjuvant chemotherapy is a positive prognostic indicator. Lastly, ctDNA has demonstrated superior sensitivity to the conventional blood tumor marker carcinoembryonic antigen (CEA) and can offer median lead times of up to 11 months for radiographic detection of recurrence during the surveillance of resected, stage I-III colorectal cancer. In metastatic colorectal cancer (mCRC), there is growing evidence to suggest that plasma ctDNA can be used to monitor tumor response to conventional chemotherapy as well. The present case series demonstrated that plasma ctDNA is a predictor of tumor response to immunotherapy in patients with mCRC that are microsatellite stable or microsatellite instability high. Plasma ctDNA could serve as a dynamic marker of immunotherapy response even in colorectal tumors that were CEA non-producers. Overall, these findings add to ongoing efforts to establish the role of plasma ctDNA in monitoring response to immunotherapy in CRC. [ABSTRACT FROM AUTHOR]

Chromosomal instability (CIN) and microsatellite instability (MSI) are two major causes of colorectal cancers. Recently, a percentage of colorectal cancers were found to be neither CIN nor MSI. This study was performed to explore whether microsatellite- and chromosomal-stable (MACS) colorectal cancers comprise a substantially distinct subtype. Sixty-nine sporadic colorectal cancers were classified into three subsets according to ploidy and microsatellite instability status: CIN+, MSI+, and MACS. Clinicopathologic, genetic, and epigenetic differences among these three groups were investigated by immunohistochemical analysis of p53, APC, hMLH1, and BAX and methylation study of p14 ARF , hMLH1, p16 INK4a , MGMT, and MINT1 with methylation-specific polymerase chain reaction. The 69 cases included 49 CIN+, 7 MSI+, and 13 MACS. MACS were found to differ from CIN+ and MSI+ in three aspects. The clinicopathologic features of MACS were similar to MSI+ but distinguished from CIN+. Comparatively, MACS preferred proximal location and poor differentiation ( p < 0.05). An immunohistochemical study demonstrated that MACS had a lower rate of loss of hMLH1 or BAX protein than MSI+ and less loss of APC protein than CIN+. In an epigenetic aspect, both MACS and MSI+ had a high rate of CpG island methylator phenotype (46.2 and 42.9%). However, they differed in the presence of hMLH1 methylation (7.7 vs 57.1%, p < 0.05). Otherwise, compared with CIN+, MACS had a more frequent CpG island methylator phenotype and MINT1 methylation ( p < 0.05) and relatively more common p16 INK4a methylation with marginal significance ( p = 0.056). MACS sporadic colorectal cancers may compose a unique phenotype with distinct clinicopathologic and molecular characteristics. [ABSTRACT FROM AUTHOR]

An early step in the carcinogenesis of hereditary non-polyposis colorectal cancer (HNPCC) and some sporadic colorectal cancers (CRCs) is the acquisition of a 'mutator phenotype' resulting from defects in DNA mismatch repair (MMR) genes, which normally maintain genomic stability. This mutator phenotype causes an approximately 100-1000-fold increase in base substitutions and small insertion/deletion mutations thereby driving carcinogenesis. It also causes genome-wide microsatellite instability (MSI) due to the inability to repair mutations within these small, hard to replicate, repetitive DNA elements. In contrast, less is known about the role of mutator phenotypes in microsatellite stable (MSS) CRC. In this report, we have measured the mutation rates in 11 MSS CRC cell lines to obtain an estimate of the prevalence of mutator phenotypes in MSS carcinogenesis. Of the 11 cell lines, three of them (27%) possess spontaneous hypoxanthine phosphoribosyltransferase mutation rates approximately 10-100-fold above background. When challenged with alkylating and oxidising agents, the degree of survival and apoptotic responses are different, indicating that these cell lines may represent more than one mutator phenotype. These data demonstrate that a significant portion of MSS CRC cell lines has increased mutation rates and that this may play a role in MSS CRC carcinogenesis. [ABSTRACT FROM AUTHOR]

ST7 is a putative tumor suppressor gene on chromosome 7q31. However, the role of ST7 as a tumor suppressor is uncertain as somatic mutations have been difficult to demonstrate.In order to investigate the genetic role of RAY1/ST7 in tumorigenesis, we have screened 135 colorectal cancers for loss of heterozygosity (LOH) at chromosome 7q31.The entire RAY1/ST7 gene, including intron/exon boundaries and alternate 5′ and 3′ sequences of 15/124 (12%) informative cancers with LOH were characterized. No somatic mutations of the RAY1/ST7 gene were observed. Our results do not support a role for RAY1/ST7 as a colorectal cancer tumor suppressor gene. [Copyright &y& Elsevier]

Simple Summary: Given that most patients with MSS mCRC do not respond to immunotherapy agents or do not have durable clinical responses, there is an unmet clinical need to obtain predictors of response to immunotherapy and rational immunotherapy-based combination therapies for this entity. In this review, we present the efforts that have been made to date in the clinical setting to develop immunotherapy-based combinations for MSS mCRC and the rationale that lies behind each strategy. In recent years, deepening knowledge of the complex interactions between the immune system and cancer cells has led to the advent of effective immunotherapies that have revolutionized the therapeutic paradigm of several cancer types. However, colorectal cancer (CRC) is one of the tumor types in which immunotherapy has proven less effective. While there is solid clinical evidence for the therapeutic role of immune checkpoint inhibitors in mismatch repair-deficient (dMMR) and in highly microsatellite instable (MSI-H) metastatic CRC (mCRC), blockade of CTLA-4 or PD-L1/PD-1 as monotherapy has not conferred any major clinical benefit to patients with MMR-proficient (pMMR) or microsatellite stable (MSS) mCRC, reflecting 95% of the CRC population. There thus remains a high unmet medical need for the development of novel immunotherapy approaches for the vast majority of patients with pMMR or MSS/MSI-low (MSI-L) mCRC. Defining the molecular mechanisms for immunogenicity in mCRC and mediating immune resistance in MSS mCRC is needed to develop predictive biomarkers and effective therapeutic combination strategies. Here we review available clinical data from combinatorial therapeutic approaches using immunotherapy-based strategies for MSS mCRC. [ABSTRACT FROM AUTHOR]

Introduction: Immunotherapy by checkpoint inhibitors, i.e., anti-programmed death-1(PD-1) or anti-programmed death-ligand 1 (PD-L1) antibodies, has gained more attention managing solid tumors. Pembrolizumab (an anti-PD-1 antibody) in metastatic colorectal cancer (CRC) was approved in 2017 by the US FDA.Pembrolizumab is not effective in microsatellite stable, mismatch-repair-proficient (MSS-pMMR) molecular phenotype, which comprises most CRC patients. In this report, we present the first case of metastatic CRC with a dramatic and durable response to pembrolizumab despite being of MSS-pMMR phenotype.A 34-year-old woman, presented seven years ago with T3N2bM0 colon cancer and an appendix carcinoid tumor. The last relapse with bilateral pulmonary metastases was refractory to all treatments. Although it seemed unresponsive to immunotherapy because of MSS molecular phenotype, due to the high expression level of PD-L1 (85%), we started treatment with pembrolizumab 200 mg every three weeks and continued for the overall 19 courses. Surprisingly, a rapid and complete response was observed that last until now, i.e., 17 months after discontinuation of pembrolizumab.Despite non-promising results in the current clinical trials, MSS-pMMR colorectal cancer patients' deprivation from immunotherapy seems not to be reasonable. There are ongoing clinical trials on checkpoint inhibitors either alone or in combination with other drugs. However, immunostaining for PD-L1 should be considered as a possible response predictor.Immunotherapy either by cell-based approaches or by checkpoint inhibitors may revolutionize cancer treatmentPembrolizumab has been approved by the FDA in 2017 for colorectal cancer.However, MSS-pMMR molecular phenotype which comprises the majority of CRC patients, has not shown a good response to checkpoint inhibitors.We present a MSS-pMMR case with complete and durable response to pembrolizumabWe suggest immunostaining for PD-L1 as a possible response predictor to checkpoint inhibitorsReason for the report: Immunotherapy by checkpoint inhibitors, i.e., anti-programmed death-1(PD-1) or anti-programmed death-ligand 1 (PD-L1) antibodies, has gained more attention managing solid tumors. Pembrolizumab (an anti-PD-1 antibody) in metastatic colorectal cancer (CRC) was approved in 2017 by the US FDA.Pembrolizumab is not effective in microsatellite stable, mismatch-repair-proficient (MSS-pMMR) molecular phenotype, which comprises most CRC patients. In this report, we present the first case of metastatic CRC with a dramatic and durable response to pembrolizumab despite being of MSS-pMMR phenotype.A 34-year-old woman, presented seven years ago with T3N2bM0 colon cancer and an appendix carcinoid tumor. The last relapse with bilateral pulmonary metastases was refractory to all treatments. Although it seemed unresponsive to immunotherapy because of MSS molecular phenotype, due to the high expression level of PD-L1 (85%), we started treatment with pembrolizumab 200 mg every three weeks and continued for the overall 19 courses. Surprisingly, a rapid and complete response was observed that last until now, i.e., 17 months after discontinuation of pembrolizumab.Despite non-promising results in the current clinical trials, MSS-pMMR colorectal cancer patients' deprivation from immunotherapy seems not to be reasonable. There are ongoing clinical trials on checkpoint inhibitors either alone or in combination with other drugs. However, immunostaining for PD-L1 should be considered as a possible response predictor.Immunotherapy either by cell-based approaches or by checkpoint inhibitors may revolutionize cancer treatmentPembrolizumab has been approved by the FDA in 2017 for colorectal cancer.However, MSS-pMMR molecular phenotype which comprises the majority of CRC patients, has not shown a good response to checkpoint inhibitors.We present a MSS-pMMR case with complete and durable response to pembrolizumabWe suggest immunostaining for PD-L1 as a possible response predictor to checkpoint inhibitorsCase summary: Immunotherapy by checkpoint inhibitors, i.e., anti-programmed death-1(PD-1) or anti-programmed death-ligand 1 (PD-L1) antibodies, has gained more attention managing solid tumors. Pembrolizumab (an anti-PD-1 antibody) in metastatic colorectal cancer (CRC) was approved in 2017 by the US FDA.Pembrolizumab is not effective in microsatellite stable, mismatch-repair-proficient (MSS-pMMR) molecular phenotype, which comprises most CRC patients. In this report, we present the first case of metastatic CRC with a dramatic and durable response to pembrolizumab despite being of MSS-pMMR phenotype.A 34-year-old woman, presented seven years ago with T3N2bM0 colon cancer and an appendix carcinoid tumor. The last relapse with bilateral pulmonary metastases was refractory to all treatments. Although it seemed unresponsive to immunotherapy because of MSS molecular phenotype, due to the high expression level of PD-L1 (85%), we started treatment with pembrolizumab 200 mg every three weeks and continued for the overall 19 courses. Surprisingly, a rapid and complete response was observed that last until now, i.e., 17 months after discontinuation of pembrolizumab.Despite non-promising results in the current clinical trials, MSS-pMMR colorectal cancer patients' deprivation from immunotherapy seems not to be reasonable. There are ongoing clinical trials on checkpoint inhibitors either alone or in combination with other drugs. However, immunostaining for PD-L1 should be considered as a possible response predictor.Immunotherapy either by cell-based approaches or by checkpoint inhibitors may revolutionize cancer treatmentPembrolizumab has been approved by the FDA in 2017 for colorectal cancer.However, MSS-pMMR molecular phenotype which comprises the majority of CRC patients, has not shown a good response to checkpoint inhibitors.We present a MSS-pMMR case with complete and durable response to pembrolizumabWe suggest immunostaining for PD-L1 as a possible response predictor to checkpoint inhibitorsOutcome: Immunotherapy by checkpoint inhibitors, i.e., anti-programmed death-1(PD-1) or anti-programmed death-ligand 1 (PD-L1) antibodies, has gained more attention managing solid tumors. Pembrolizumab (an anti-PD-1 antibody) in metastatic colorectal cancer (CRC) was approved in 2017 by the US FDA.Pembrolizumab is not effective in microsatellite stable, mismatch-repair-proficient (MSS-pMMR) molecular phenotype, which comprises most CRC patients. In this report, we present the first case of metastatic CRC with a dramatic and durable response to pembrolizumab despite being of MSS-pMMR phenotype.A 34-year-old woman, presented seven years ago with T3N2bM0 colon cancer and an appendix carcinoid tumor. The last relapse with bilateral pulmonary metastases was refractory to all treatments. Although it seemed unresponsive to immunotherapy because of MSS molecular phenotype, due to the high expression level of PD-L1 (85%), we started treatment with pembrolizumab 200 mg every three weeks and continued for the overall 19 courses. Surprisingly, a rapid and complete response was observed that last until now, i.e., 17 months after discontinuation of pembrolizumab.Despite non-promising results in the current clinical trials, MSS-pMMR colorectal cancer patients' deprivation from immunotherapy seems not to be reasonable. There are ongoing clinical trials on checkpoint inhibitors either alone or in combination with other drugs. However, immunostaining for PD-L1 should be considered as a possible response predictor.Immunotherapy either by cell-based approaches or by checkpoint inhibitors may revolutionize cancer treatmentPembrolizumab has been approved by the FDA in 2017 for colorectal cancer.However, MSS-pMMR molecular phenotype which comprises the majority of CRC patients, has not shown a good response to checkpoint inhibitors.We present a MSS-pMMR case with complete and durable response to pembrolizumabWe suggest immunostaining for PD-L1 as a possible response predictor to checkpoint inhibitorsGraphical abstract: Immunotherapy by checkpoint inhibitors, i.e., anti-programmed death-1(PD-1) or anti-programmed death-ligand 1 (PD-L1) antibodies, has gained more attention managing solid tumors. Pembrolizumab (an anti-PD-1 antibody) in metastatic colorectal cancer (CRC) was approved in 2017 by the US FDA.Pembrolizumab is not effective in microsatellite stable, mismatch-repair-proficient (MSS-pMMR) molecular phenotype, which comprises most CRC patients. In this report, we present the first case of metastatic CRC with a dramatic and durable response to pembrolizumab despite being of MSS-pMMR phenotype.A 34-year-old woman, presented seven years ago with T3N2bM0 colon cancer and an appendix carcinoid tumor. The last relapse with bilateral pulmonary metastases was refractory to all treatments. Although it seemed unresponsive to immunotherapy because of MSS molecular phenotype, due to the high expression level of PD-L1 (85%), we started treatment with pembrolizumab 200 mg every three weeks and continued for the overall 19 courses. Surprisingly, a rapid and complete response was observed that last until now, i.e., 17 months after discontinuation of pembrolizumab.Despite non-promising results in the current clinical trials, MSS-pMMR colorectal cancer patients' deprivation from immunotherapy seems not to be reasonable. There are ongoing clinical trials on checkpoint inhibitors either alone or in combination with other drugs. However, immunostaining for PD-L1 should be considered as a possible response predictor.Immunotherapy either by cell-based approaches or by checkpoint inhibitors may revolutionize cancer treatmentPembrolizumab has been approved by the FDA in 2017 for colorectal cancer.However, MSS-pMMR molecular phenotype which comprises the majority of CRC patients, has not shown a good response to checkpoint inhibitors.We present a MSS-pMMR case with complete and durable response to pembrolizumabWe suggest immunostaining for PD-L1 as a possible response predictor to checkpoint inhibitors [ABSTRACT FROM AUTHOR]

Simple Summary: More emerging studies are exploring immunotherapy for solid cancers, including colorectal cancer. Besides, checkpoint blockade immunotherapy and chimeric antigen receptor (CAR) -based immune cell therapy have being examined in clinical trials for colorectal cancer patients. However, immunosuppression that leads to the blockage of normal immunosurveillance often leads to cancer development and relapse. In this study, we systematically reviewed the mechanism of immunosuppression, specifically in colorectal cancer, from different perspectives, including the natural or induced immunosuppressive cells, cell surface protein, cytokines/chemokines, transcriptional factors, metabolic alteration, phosphatase, and tissue hypoxia in the tumor microenvironment. We also discussed the progress of immunotherapies in clinical trials/studies for colorectal cancer and highlighted how different strategies for cancer therapy targeted the immunosuppression reviewed above. Our review provides some timely implications for restoring immunosurveillance to improve treatment efficacy in colorectal cancer (CRC). CRC is the third most diagnosed cancer in the US with the second-highest mortality rate. A multi-modality approach with surgery/chemotherapy is used in patients with early stages of colon cancer. Radiation therapy is added to the armamentarium in patients with locally advanced rectal cancer. While some patients with metastatic CRC are cured, the majority remain incurable and receive palliative chemotherapy as the standard of care. Recently, immune checkpoint blockade has emerged as a promising treatment for many solid tumors, including CRC with microsatellite instability. However, it has not been effective for microsatellite stable CRC. Here, main mechanisms of immunosuppression in CRC will be discussed, aiming to provide some insights for restoring immunosurveillance to improve treatment efficacy in CRC. [ABSTRACT FROM AUTHOR]

The introduction of checkpoint inhibitors provided remarkable achievements in several solid tumors but only 5% of metastatic colorectal cancer (mCRC) patients, i.e., those with bearing microsatellite instable (MSI-high)/deficient DNA mismatch repair (dMMR) tumors, benefit from this approach. The favorable effect of immunotherapy in these patients has been postulated to be due to an increase in neoantigens due to their higher somatic mutational load, also associated with an abundant infiltration of immune cells in tumor microenvironment (TME). While in patients with dMMR tumors checkpoint inhibitors allow achieving durable response with dramatic survival improvement, current results in patients with microsatellite stable (MSS or MSI-low)/proficient DNA mismatch repair (pMMR) tumors are disappointing. These tumors show low mutational load and absence of "immune-competent" TME, and are intrinsically resistant to immune checkpoint inhibitors. Modifying the interplay among cancer cells, TME and host immune system is the aim of multiple lines of research in order to enhance the immunogenicity of pMMR mCRC, and exploit immunotherapy also in this field. Here, we focus on the rationale behind ongoing clinical trials aiming at extending the efficacy of immunotherapy beyond the MSI-high/dMMR subgroup with particular regard to academic no-profit studies. [ABSTRACT FROM AUTHOR]

Microsatellite stable (MSS) BRAF p.V600E mutation colorectal cancer (BRAF-CRC) has a poor prognosis, whereas microsatellite instability (MSI) in BRAF-CRC is associated with a favorable prognosis. Although usually considered a single clinical entity, the MSI BRAF-CRC subtype shows some distinct characteristics in comparison with the MSS BRAF-CRC subtype. We conducted a meta-analysis to investigate the influence of clinicopathological features on MSI status in BRAF-CRC. We searched publications up to March 2019 from PubMed, Embase, and the Cochrane Library. The effect of MSI status on outcome parameters was assessed using odds ratios (ORs) with 95% confidence intervals (CIs) and fixed- or random-effects models according to the heterogeneity. After reviewing 2839 reports, 16 eligible studies including 1381 patients with BRAF-CRC met the criteria. The MSI BRAF-CRC subtype was associated with older age, female sex (OR = 1.70; 95% CI = 1.35–2.14; P < 0.00001), proximal tumor location (OR = 5.10; 95% CI = 3.70–7.03; P < 0.00001), early TNM stage (OR = 5.28; 95% CI = 3.93–7.09; P < 0.00001), and poor differentiation (OR = 2.29; 95% CI = 1.60–3.28; P < 0.00001). MSI was significantly correlated with distinct favorable clinicopathological characteristics in BRAF-CRC. These results suggest that MSI status should be considered as a stratification factor for better management of the BRAF-CRC. [ABSTRACT FROM AUTHOR]

Checkpoint inhibitor therapy has introduced a revolution in contemporary anticancer therapy. It has led to dramatic improvements in patient outcomes and has spawned tremendous research into novel immunomodulatory agents and combination therapy that has changed the trajectory of cancer care. However, clinical benefit in patients with colorectal cancer has been generally limited to tumors with loss of mismatch repair function and those with specific germline mutations in the DNA polymerase gene. Unfortunately, tumors with these specific mutator phenotypes are in the minority. Recent pre-clinical and clinical studies have begun to reveal encouraging results suggesting that checkpoint inhibitor therapy can be expanded to an increasing number of colorectal tumors with microsatellite stability and the absence of traditional predictive biomarkers of checkpoint inhibitor response. These studies generally rely on combinations of checkpoint inhibitors with chemotherapy, molecular targeted therapy, radiation therapy, or other novel immunomodulatory agents. This article will review the most current data in microsatellite stable colorectal cancer. [ABSTRACT FROM AUTHOR]