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Most EGFR exon 20 insertion (EGFRex20ins) driver mutations in non–small cell lung cancer (NSCLC) are insensitive to approved EGFR tyrosine kinase inhibitors (TKI). To address the limitations of existing therapies targeting EGFR-mutated NSCLC, mobocertinib (TAK-788), a novel irreversible EGFR TKI, was specifically designed to potently inhibit oncogenic variants containing activating EGFRex20ins mutations with selectivity over wild-type EGFR. The in vitro and in vivo activity of mobocertinib was evaluated in engineered and patient-derived models harboring diverse EGFRex20ins mutations. Mobocertinib inhibited viability of various EGFRex20ins-driven cell lines more potently than approved EGFR TKIs and demonstrated in vivo antitumor efficacy in patient-derived xenografts and murine orthotopic models. These findings support the ongoing clinical development of mobocertinib for the treatment of EGFRex20ins-mutated NSCLC.Significance:No oral EGFR-targeted therapies are approved for EGFR exon 20 insertion (EGFRex20ins) mutation-driven NSCLC. Mobocertinib is a novel small-molecule EGFR inhibitor specifically designed to target EGFRex20ins mutants. Preclinical data reported here support the clinical development of mobocertinib in patients with NSCLC with EGFR exon 20 insertion mutations.See related commentary by Pacheco, p. 1617.This article is highlighted in the In This Issue feature, p. 1601

KRAS mutation is present in approximately 30% of human lung adenocarcinomas. Although recent advances in targeted therapy have shown great promise, effective targeting of KRAS remains elusive, and concurrent alterations in tumor suppressors render KRAS-mutant tumors even more resistant to existing therapies. Contributing to the refractoriness of KRAS-mutant tumors are immunosuppressive mechanisms, such as increased presence of suppressive regulatory T cells (Treg) in tumors and elevated expression of the inhibitory receptor PD-1 on tumor-infiltrating T cells. Treatment with BET bromodomain inhibitors is beneficial for hematologic malignancies, and they have Treg-disruptive effects in a non–small cell lung cancer (NSCLC) model. Targeting PD-1–inhibitory signals through PD-1 antibody blockade also has substantial therapeutic impact in lung cancer, although these outcomes are limited to a minority of patients. We hypothesized that the BET bromodomain inhibitor JQ1 would synergize with PD-1 blockade to promote a robust antitumor response in lung cancer. In the present study, using Kras+/LSL-G12D; Trp53L/L (KP) mouse models of NSCLC, we identified cooperative effects between JQ1 and PD-1 antibody. The numbers of tumor-infiltrating Tregs were reduced and activation of tumor-infiltrating T cells, which had a T-helper type 1 (Th1) cytokine profile, was enhanced, underlying their improved effector function. Furthermore, lung tumor–bearing mice treated with this combination showed robust and long-lasting antitumor responses compared with either agent alone, culminating in substantial improvement in the overall survival of treated mice. Thus, combining BET bromodomain inhibition with immune checkpoint blockade offers a promising therapeutic approach for solid malignancies such as lung adenocarcinoma. Cancer Immunol Res; 6(10); 1234–45. ©2018 AACR.

Effective therapies for non–small cell lung cancer (NSCLC) remain challenging despite an increasingly comprehensive understanding of somatically altered oncogenic pathways. It is now clear that therapeutic agents with potential to impact the tumor immune microenvironment potentiate immune-orchestrated therapeutic benefit. Herein, we evaluated the immunoregulatory properties of histone deacetylase (HDAC) and bromodomain inhibitors, two classes of drugs that modulate the epigenome, with a focus on key cell subsets that are engaged in an immune response. By evaluating human peripheral blood and NSCLC tumors, we show that the selective HDAC6 inhibitor ricolinostat promotes phenotypic changes that support enhanced T-cell activation and improved function of antigen-presenting cells. The bromodomain inhibitor JQ1 attenuated CD4+FOXP3+ T regulatory cell suppressive function and synergized with ricolinostat to facilitate immune-mediated tumor growth arrest, leading to prolonged survival of mice with lung adenocarcinomas. Collectively, our findings highlight the immunomodulatory effects of two epigenetic modifiers that, together, promote T cell–mediated antitumor immunity and demonstrate their therapeutic potential for treatment of NSCLC.Significance: Selective inhibition of HDACs and bromodomain proteins modulates tumor-associated immune cells in a manner that favors improved T-cell function and reduced inhibitory cellular mechanisms. These effects facilitated robust antitumor responses in tumor-bearing mice, demonstrating the therapeutic potential of combining these epigenetic modulators for the treatment of NSCLC. Cancer Discov; 7(8); 852–67. ©2017 AACR.This article is highlighted in the In This Issue feature, p. 783

Supplementary Table 1. HDAC inhibitors tested with healthy donor PBMCs and their biochemical potency (nM) across HDACs 1, 2, 3, and 6. Supplementary Table 2. Information for consented Non-small cell lung cancer (NSCLC) patients that underwent surgical resectioning as part of their treatment plan and whose tumor specimen and blood samples obtained after surgery were analyzed. Supplementary Figure 1. Reduced CD4+FOXP3+ Treg cells in healthy donor and NSCLC patient PBMC in the presence of ricolinostat. Supplementary Figure 2. Up-regulation of CD69 on T cells in healthy donor PBMC cultures in the presence of ricolinostat. Supplementary Figure 3. Viability of immune cells within dissociated tumor specimens cultured in the presence of ricolinostat or entinostat. Supplementary Figure 4. Effector function of T cells within 2-D cultures of disaggregated tumor specimens from NSCLC patients. Supplementary Figure 5. Increased expression of MHC class II and CD86 on monocytes in healthy donor PBMC in the presence of ricolinostat. Supplementary Figure 6. Phenotype of T cells infiltrating lung tumors of genetically engineered mice treated with ricolinostat. Supplementary Figure 7. Gene expression profile of Tumor-infiltrating T cells. Supplementary Figure 8. Ricolinostat promotes up-regulation of MHC class II and CD86 on tumor-associated macrophages. Supplementary figure 9. Immunohistochemical and flow cytometric analyses of acetylated α-tubulin in lung tumors of KP mice. Supplementary Figure 10. Kinetics of tumor growth in KP mice treated with ricolinostat. Supplementary Figure 11. Phenotype of tumor-infiltrating T cell subsets in lung tumors of KP mice treated with JQ1. Supplementary Figure 12. Immunohistochemical and flow cytometric analyses of phospho-STAT5 levels in lung tumors of KP mice. Supplementary Figure 13. Suppressive function of Tregs isolated from the spleen of lung tumor-bearing KP mice treated with JQ1. Supplementary Figure 14. Phenotype of Tregs in the spleen or lung tumors of genetically engineered mouse models (GEMM) of NSCLC. Supplementary Figure 15. Phenotype of Tregs within cultures of dissociated tumor specimen from NSCLC patients. Supplementary Figure 17. Histology and immunohistochemical staining of lung tumor sections from treated KP mice. Supplementary Figure 18. Kinetics of tumor growth in TL or wild-type mice. Supplementary Figure 19. Quantification of T cell subsets and TAMs in tumors of KP mice. Supplementary Figure 20. Phenotype of CD8+T cells infiltrating lung tumors of treated KP mice. Supplementary Figure 21. Gene expression profile of tumor-infiltrating macrophages (TAMs) in treated KP mice. Supplementary Figure 22. Gene expression profile of tumor-infiltrating macrophages T cells in treated KP mice. Supplementary Figure 23. Proportion of CD4+Foxp3+ Tregs present within tumor-infiltrating T cells utilized in gene expression studies. Supplementary Figure 24. Gating strategy. Supplementary Figure 25. Correlation plot for the expression of indicated genes in CD45+ leukocytes in KP tumors as evaluated by single cell RNA-Sequencing.

figure legends for supplementary Table S1-S3 and supplementary Figure S1-S13

Supplementary Tables (S1-6) and Figures (S1-6)

GSEA analysis of mobocertinib and T-DM1 treated tumors versus mobocertinib-only treated tumors Genes involved in "INTERFERON ALPHA RESPONSE", "INFLAMMATORY RESPONSE", "INTERFERON GAMMA RESPONSE", "IL2 STAT5 SIGNALING", "TNFA SIGNALING VIA NFKB" and "IL6 JAK STAT3 SIGNALING" pathways of HALLMARK gene sets.

No targeted treatments are currently approved for HER2 exon 20 insertion–mutant lung adenocarcinoma patients. Mobocertinib (TAK-788) is a potent irreversible tyrosine kinase inhibitor (TKI) designed to target human epidermal growth factor receptor 2 (HER2/ERBB2) exon 20 insertion mutations. However, the function of mobocertinib on HER2 exon 20 insertion–mutant lung cancer is still unclear. Here we conducted systematic characterization of preclinical models to understand the activity profile of mobocertinib against HER2 exon 20 insertions. In HER2 exon 20 insertion–mutant cell lines, the IC50 of mobocertinib was higher than poziotinib and comparable with or slightly lower than afatinib, neratinib, and pyrotinib. Mobocertinib had the lowest HER2 exon 20 insertion IC50/wild-type (WT) EGFR IC50 ratio, indicating that mobocertinib displayed the best selectivity profile in these models. Also, mobocertinib showed strong inhibitory activity in HER2 exon 20YVMA allograft and patient-derived xenograft models. In genetically engineered mouse models, HER2 exon 20G776>VC lung tumors exhibited a sustained complete response to mobocertinib, whereas HER2 exon 20YVMA tumors showed only partial and transient response. Combined treatment with a second antibody–drug conjugate (ADC) against HER2, ado-trastuzumab emtansine (T-DM1), synergized with mobocertinib in HER2 exon 20YVMA tumors. In addition to the tumor cell autonomous effect, sustained tumor growth control derived from M1 macrophage infiltration and CD4+ T-cell activation. These findings support the ongoing clinical development of mobocertinib (NCT02716116) and provide a rationale for future clinical evaluation of T-DM1 combinational therapy in HER2 exon 20YVMA insertion–mutant lung adenocarcinoma patients.Significance:This study elucidates the potent inhibitory activity of mobocertinib against HER2 exon 20 insertion–mutant lung cancer and the synergic effect of combined mobocertinib and T-DM1, providing a strong rationale for clinical investigation.

Figure S1

Supplemental Figure 1. Characterization of DFCI 359 and DFCI 315.

Figure legends for supplementary Figure S1-S3

Table S1. sgRNA and PAM sequences; Table S2. The IC50 values for AZD2014 and AZD1775 in NSCLC cells; Table S3. Mutational status of human cell line models; Table S4. CalcuSyn combination indices; Figure S1. Dose response curves; Figure S2. Combined mTOR and WEE1 inhibition induces synergistic apoptotic caspase activity; Figure S3. Combination treatment suppresses human KRAS-driven tumor xenografted growth; Figure S4. Mice with active KRAS-driven lung cancer show significant tumor response upon dual AZD1775 and AZD2014 therapy; Figure S5. Rad51 foci-forming ability of NSCLC cells in response to gemcitabine and etoposide treatment; Figure S6. Ectopic expression of LKB1 is sufficient to overcome the loss of the LKB1-mediated sensitization to dual AZD2014 and AZD1775 therapy; Figure S7. Loss of LKB1 in KRAS-mutant cell lines confers partial resistance to dual WEE1 and mTOR therapy; Figure S8. Ectopic expression of LKB1 is sufficient to overcome the loss of the LKB1-mediated sensitization to dual AZD2014 and AZD1775 therapy.

Purpose: HER2 (or ERBB2) aberrations, including both amplification and mutations, have been classified as oncogenic drivers that contribute to 2% to 6% of lung adenocarcinomas. HER2 amplification is also an important mechanism for acquired resistance to EGFR tyrosine kinase inhibitors (TKI). However, due to limited preclinical studies and clinical trials, currently there is still no available standard of care for lung cancer patients with HER2 aberrations. To fulfill the clinical need for targeting HER2 in patients with non–small cell lung cancer (NSCLC), we performed a comprehensive preclinical study to evaluate the efficacy of a third-generation TKI, osimertinib (AZD9291).Experimental Design: Three genetically modified mouse models (GEMM) mimicking individual HER2 alterations in NSCLC were generated, and osimertinib was tested for its efficacy against these HER2 aberrations in vivo.Results: Osimertinib treatment showed robust efficacy in HER2wt overexpression and EGFR del19/HER2 models, but not in HER2 exon 20 insertion tumors. Interestingly, we further identified that combined treatment with osimertinib and the BET inhibitor JQ1 significantly increased the response rate in HER2-mutant NSCLC, whereas JQ1 single treatment did not show efficacy.Conclusions: Overall, our data indicated robust antitumor efficacy of osimertinib against multiple HER2 aberrations in lung cancer, either as a single agent or in combination with JQ1. Our study provides a strong rationale for future clinical trials using osimertinib either alone or in combination with epigenetic drugs to target aberrant HER2 in patients with NSCLC. Clin Cancer Res; 24(11); 2594–604. ©2018 AACR.See related commentary by Cappuzzo and Landi, p. 2470

Characteristics of SCLC cell lines

Supplementary Figures 1-5

This section contains 10 supplemental figures and related figure legends.

Small-cell lung cancer (SCLC) has the highest malignancy among all lung cancers, exhibiting aggressive growth and early metastasis to distant sites. For 30 years, treatment options for SCLC have been limited to chemotherapy, warranting the need for more effective treatments. Frequent inactivation of TP53 and RB1 as well as histone dysmodifications in SCLC suggest that transcriptional and epigenetic regulations play a major role in SCLC disease evolution. Here we performed a synthetic lethal screen using the BET inhibitor JQ1 and an shRNA library targeting 550 epigenetic genes in treatment-refractory SCLC xenograft models and identified HDAC6 as a synthetic lethal target in combination with JQ1. Combined treatment of human and mouse SCLC cell line–derived xenograft tumors with the HDAC6 inhibitor ricolinostat (ACY-1215) and JQ1 demonstrated significant inhibition of tumor growth; this effect was abolished upon depletion of NK cells, suggesting that these innate immune lymphoid cells play a role in SCLC tumor treatment response. Collectively, these findings suggest a potential new treatment for recurrent SCLC.Significance: These findings identify a novel therapeutic strategy for SCLC using a combination of HDAC6 and BET inhibitors. Cancer Res; 78(13); 3709–17. ©2018 AACR.

Purpose: KRAS-activating mutations are the most common oncogenic driver in non–small cell lung cancer (NSCLC), but efforts to directly target mutant KRAS have proved a formidable challenge. Therefore, multitargeted therapy may offer a plausible strategy to effectively treat KRAS-driven NSCLCs. Here, we evaluate the efficacy and mechanistic rationale for combining mTOR and WEE1 inhibition as a potential therapy for lung cancers harboring KRAS mutations.Experimental Design: We investigated the synergistic effect of combining mTOR and WEE1 inhibitors on cell viability, apoptosis, and DNA damage repair response using a panel of human KRAS-mutant and wild type NSCLC cell lines and patient-derived xenograft cell lines. Murine autochthonous and human transplant models were used to test the therapeutic efficacy and pharmacodynamic effects of dual treatment.Results: We demonstrate that combined inhibition of mTOR and WEE1 induced potent synergistic cytotoxic effects selectively in KRAS-mutant NSCLC cell lines, delayed human tumor xenograft growth and caused tumor regression in a murine lung adenocarcinoma model. Mechanistically, we show that inhibition of mTOR potentiates WEE1 inhibition by abrogating compensatory activation of DNA repair, exacerbating DNA damage in KRAS-mutant NSCLC, and that this effect is due in part to reduction in cyclin D1.Conclusions: These findings demonstrate that compromised DNA repair underlies the observed potent synergy of WEE1 and mTOR inhibition and support clinical evaluation of this dual therapy for patients with KRAS-mutant lung cancers. Clin Cancer Res; 23(22); 6993–7005. ©2017 AACR.

Supplementary Table 1

Supplementary Table S1

Fig S1. Copy number of human HER2 in HW mice (A) Blood sample was collected from HW mouse and used for fluorescence in situ hybridization (FISH) with hHER2 gene labeled in red/orange and internal 2-copy control D15Mit224 labeled in green. (B) Summary of hHER2 copy number using both FISH and real-time qPCR. gDNA was extracted from HW mouse ear tissues and real-time qPCR based copy number assay was performed to identify the copy number of human HER2. The 2-copy mouse TERT gene was used as internal control. Fig. S2 Tumor growth curve and the overall survival curve of HW mice with doxy induction (A) Tumor growth curve for 16 weeks from MRI data. (B) Overall survival curve of HW mice after doxycycline food induction. Fig. S3 Efficacy of erlotinib and osimertinib against EGFR-del19 lung tumors Del19 mice were treated with either erlotinib or osimertinib for 4 weeks and tumor volume change is shown as waterfall plot. Each column shows one mouse.

Purpose:Evaluating drug responses using primary patient-derived cells ex vivo represents a potentially rapid and efficient approach to screening for new treatment approaches. Here, we sought to identify neratinib combinations in HER2 mutant non–small cell lung cancer (NSCLC) patient xenograft-derived organotypic spheroids (XDOTS) using a short-term ex vivo system.Experimental Design:We generated two HER2-mutant NSCLC PDX models [DFCI359 (HER2 exon19 755_757LREdelinsRP) and DFCI315 (HER2 exon20 V777_G778insGSP)] and used the PDX tumors to generate XDOTS. Tumor spheroids were grown in a microfluidic device and treated ex vivo with neratinib-based drug combinations. Live/dead quantification was performed by dual-labeling deconvolution fluorescence microscopy. The most efficacious ex vivo combination was subsequently validated in vivo using the DFCI359 and DFCI315 PDXs and a HER2YVMA genetically engineered mouse model.Results:Both neratinib and afatinib, but not gefitinib, induced cell death in DFCI359 XDOTS. The combinations of neratinib/trastuzumab and neratinib/temsirolimus enhanced the therapeutic benefit of neratinib alone in DFCI315 and DFCI359. The combination of neratinib and trastuzumab in vivo was more effective compared with single-agent neratinib or trastuzumab and was associated with more robust inhibition of HER2 and downstream signaling.Conclusions:The XDOTS platform can be used to evaluate therapies and therapeutic combinations ex vivo using PDX tumors. This approach may accelerate the identification and clinical development of therapies for targets with no or few existing models and/or therapies.

Supplemental Legend

Purpose: Despite the challenge to directly target mutant KRAS due to its high GTP affinity, some agents are under development against downstream signaling pathways, such as MEK inhibitors. However, it remains controversial whether MEK inhibitors can boost current chemotherapy in KRAS-mutant lung tumors in clinic. Considering the genomic heterogeneity among patients with lung cancer, it is valuable to test potential therapeutics in KRAS mutation–driven mouse models.Experimental Design: We first compared the pERK1/2 level in lung cancer samples with different KRAS substitutions and generated a new genetically engineered mouse model whose tumor was driven by KRASG12C, the most common KRAS mutation in lung cancer. Next, we evaluated the efficacy of selumetinib or its combination with chemotherapy, in KRASG12C tumors compared with KRASG12D tumors. Moreover, we generated KRASG12C/p53R270H model to explore the role of a dominant negative p53 mutation detected in patients in responsiveness to MEK inhibition.Results: We determined higher pERK1/2 in KRASG12C lung tumors compared with KRASG12D. Using mouse models, we further identified that KRASG12C tumors are significantly more sensitive to selumetinib compared with KrasG12D tumors. MEK inhibition significantly increased chemotherapeutic efficacy and progression-free survival of KRASG12C mice. Interestingly, p53 co-mutation rendered KRASG12C lung tumors less sensitive to combination treatment with selumetinib and chemotherapy.Conclusions: Our data demonstrate that unique KRAS mutations and concurrent mutations in tumor-suppressor genes are important factors for lung tumor responses to MEK inhibitor. Our preclinical study supports further clinical evaluation of combined MEK inhibition and chemotherapy for lung cancer patients harboring KRASG12C and wild-type p53 status. Clin Cancer Res; 24(19); 4854–64. ©2018 AACR.

No targeted treatments are currently approved for HER2 exon 20 insertion–mutant lung adenocarcinoma patients. Mobocertinib (TAK-788) is a potent irreversible tyrosine kinase inhibitor (TKI) designed to target human epidermal growth factor receptor 2 (HER2/ERBB2) exon 20 insertion mutations. However, the function of mobocertinib on HER2 exon 20 insertion–mutant lung cancer is still unclear. Here we conducted systematic characterization of preclinical models to understand the activity profile of mobocertinib against HER2 exon 20 insertions. In HER2 exon 20 insertion–mutant cell lines, the IC50 of mobocertinib was higher than poziotinib and comparable with or slightly lower than afatinib, neratinib, and pyrotinib. Mobocertinib had the lowest HER2 exon 20 insertion IC50/wild-type (WT) EGFR IC50 ratio, indicating that mobocertinib displayed the best selectivity profile in these models. Also, mobocertinib showed strong inhibitory activity in HER2 exon 20YVMA allograft and patient-derived xenograft models. In genetically engineered mouse models, HER2 exon 20G776>VC lung tumors exhibited a sustained complete response to mobocertinib, whereas HER2 exon 20YVMA tumors showed only partial and transient response. Combined treatment with a second antibody–drug conjugate (ADC) against HER2, ado-trastuzumab emtansine (T-DM1), synergized with mobocertinib in HER2 exon 20YVMA tumors. In addition to the tumor cell autonomous effect, sustained tumor growth control derived from M1 macrophage infiltration and CD4+ T-cell activation. These findings support the ongoing clinical development of mobocertinib (NCT02716116) and provide a rationale for future clinical evaluation of T-DM1 combinational therapy in HER2 exon 20YVMA insertion–mutant lung adenocarcinoma patients. Significance: This study elucidates the potent inhibitory activity of mobocertinib against HER2 exon 20 insertion–mutant lung cancer and the synergic effect of combined mobocertinib and T-DM1, providing a strong rationale for clinical investigation.

Purpose: Evaluating drug responses using primary patient-derived cells ex vivo represents a potentially rapid and efficient approach to screening for new treatment approaches. Here, we sought to identify neratinib combinations in HER2 mutant non–small cell lung cancer (NSCLC) patient xenograft-derived organotypic spheroids (XDOTS) using a short-term ex vivo system. Experimental Design: We generated two HER2-mutant NSCLC PDX models [DFCI359 (HER2 exon19 755_757LREdelinsRP) and DFCI315 (HER2 exon20 V777_G778insGSP)] and used the PDX tumors to generate XDOTS. Tumor spheroids were grown in a microfluidic device and treated ex vivo with neratinib-based drug combinations. Live/dead quantification was performed by dual-labeling deconvolution fluorescence microscopy. The most efficacious ex vivo combination was subsequently validated in vivo using the DFCI359 and DFCI315 PDXs and a HER2YVMA genetically engineered mouse model. Results: Both neratinib and afatinib, but not gefitinib, induced cell death in DFCI359 XDOTS. The combinations of neratinib/trastuzumab and neratinib/temsirolimus enhanced the therapeutic benefit of neratinib alone in DFCI315 and DFCI359. The combination of neratinib and trastuzumab in vivo was more effective compared with single-agent neratinib or trastuzumab and was associated with more robust inhibition of HER2 and downstream signaling. Conclusions: The XDOTS platform can be used to evaluate therapies and therapeutic combinations ex vivo using PDX tumors. This approach may accelerate the identification and clinical development of therapies for targets with no or few existing models and/or therapies.

Pancreatic ductal adenocarcinoma (PDAC) is a devastating cancer with 5-year overall survival of less than 10% and few effective therapies. Here, we demonstrate that cyclin dependent kinase 7 (CDK7) is essential for the proliferation and viability of PDAC cells by showing potent anti-tumor efficacy for the CDK7-specific inhibitor YKL-5-124 in preclinical PDAC models. Selective CDK7 inhibition leads to G2/M cell cycle arrest and apoptosis in PDAC, while mediating a more modest transcriptional response compared with multi-targeted CDK7 inhibitors. YKL-5-124 treatment impairs DNA damage repair pathways in PDAC cells and evokes genomic instability by inducing R-loop formation and DNA replication stress in telomeric regions leading to chromosomal bridging and micronuclei formation. Furthermore, we demonstrate that selective CDK7 inhibition has in vitro and in vivo combinatorial efficacy with gemcitabine chemotherapy through pronounced induction of replication stress and apoptosis. Collectively, these findings support selective CDK7 inhibition as a promising therapeutic strategy for PDAC. Citation Format: Annan Yang, Jie Jiang, Ziyue Li, Kevin S. Kapner, Hanrong Feng, Kristen E. Lowder, Miljan Kuljanin, Whiteny Johnson, Giselle Uribe, Jasper E. Neggers, Shengwu Liu, Tinghu Zhang, James Decaprio, Ewa Sicinska, Brian M. Wolpin, Nicholas P. Kwiatkowski, Stephanie K. Dougan, Joseph D. Mancias, Nathanael S. Gray, Andrew J. Aguirre. Therapeutic efficacy of selective CDK7 inhibition in pancreatic cancer mediated by induction of R-loop formation, DNA replication stress and genomic instability [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr A057.

BACKGROUND: Clinical trials of the KRAS inhibitors adagrasib and sotorasib have shown promising activity in cancers harboring KRAS glycine-to-cysteine amino acid substitutions at codon 12 (KRAS(G12C)). The mechanisms of acquired resistance to these therapies are currently unknown. METHODS: Among patients with KRAS(G12C)-mutant cancers treated with adagrasib monotherapy, we performed genomic and histologic analyses that compared pretreatment samples with those obtained after the development of resistance. Cell-based experiments were conducted to study mutations that confer resistance to KRAS(G12C) inhibitors. RESULTS: A total of 38 patients were included in this study: 27 with non–small-cell lung cancer, 10 with colorectal cancer, and 1 with appendiceal cancer. Putative mechanisms of resistance to adagrasib were detected in 17 patients (45% of the cohort), of whom 7 (18% of the cohort) had multiple coincident mechanisms. Acquired KRAS alterations included G12D/R/V/W, G13D, Q61H, R68S, H95D/Q/R, Y96C, and high-level amplification of the KRAS(G12C) allele. Acquired bypass mechanisms of resistance included MET amplification; activating mutations in NRAS, BRAF, MAP2K1, and RET; oncogenic fusions involving ALK, RET, BRAF, RAF1, and FGFR3; and loss-of-function mutations in NF1 and PTEN. In two of nine patients with lung adenocarcinoma for whom paired tissue-biopsy samples were available, histologic transformation to squamous-cell carcinoma was observed without identification of any other resistance mechanisms. Using an in vitro deep mutational scanning screen, we systematically defined the landscape of KRAS mutations that confer resistance to KRAS(G12C) inhibitors. CONCLUSIONS: Diverse genomic and histologic mechanisms impart resistance to covalent KRAS(G12C) inhibitors, and new therapeutic strategies are required to delay and overcome this drug resistance in patients with cancer. (Funded by Mirati Therapeutics and others; ClinicalTrials.gov number, NCT03785249.)

No targeted treatments are currently approved for HER2 exon 20 insertion-mutant lung adenocarcinoma patients. Mobocertinib (TAK-788) is a potent irreversible tyrosine kinase inhibitor (TKI) designed to target human epidermal growth factor receptor 2 (HER2/ERBB2) exon 20 insertion mutations. However, the function of mobocertinib on HER2 exon 20 insertion-mutant lung cancer is still unclear. Here we conducted systematic characterization of pre-clinical models to understand the activity profile of mobocertinib against HER2 exon 20 insertions. In HER2 exon 20 insertion mutant cell lines, the IC(50) of mobocertinib was higher than poziotinib and comparable or slightly lower than afatinib, neratinib, and pyrotinib. Mobocertinib had the lowest HER2 exon 20 insertion IC(50) / WT EGFR IC(50) ratio, indicating that mobocertinib displayed the best selectivity profile in these models. Also, mobocertinib showed strong inhibitory activity in HER2 exon 20(YVMA) allograft and patient-derived xenograft models. In genetically engineered mouse models, HER2 exon 20(G776>VC) lung tumors exhibited a sustained complete response to mobocertinib, while HER2 exon 20(YVMA) tumors showed only partial and transient response. Combined treatment with a second antibody-drug conjugate (ADC) against HER2, ado-trastuzumab emtansine (T-DM1) synergized with mobocertinib in HER2 exon 20(YVMA) tumors. In addition to the tumor cell autonomous effect, sustained tumor growth control derived from M1 macrophage infiltration and CD4(+) T cell activation. These findings support the ongoing clinical development of mobocertinib (NCT02716116) and provide a rationale for future clinical evaluation of T-DM1 combinational therapy in HER2 exon 20(YVMA) insertion-mutant lung adenocarcinoma patients.

Most

KRAS mutation is present in approximately 30% of human lung adenocarcinomas. Although recent advances in targeted therapy have shown great promise, effective targeting of KRAS remains elusive, and concurrent alterations in tumor suppressors render KRAS-mutant tumors even more resistant to existing therapies. Contributing to the refractoriness of KRAS-mutant tumors are immunosuppressive mechanisms, such as increased presence of suppressive regulatory T cells (Treg) in tumors and elevated expression of the inhibitory receptor PD-1 on tumor-infiltrating T cells. Treatment with BET bromodomain inhibitors is beneficial for hematologic malignancies, and they have Treg-disruptive effects in a non–small cell lung cancer (NSCLC) model. Targeting PD-1–inhibitory signals through PD-1 antibody blockade also has substantial therapeutic impact in lung cancer, although these outcomes are limited to a minority of patients. We hypothesized that the BET bromodomain inhibitor JQ1 would synergize with PD-1 blockade to promote a robust antitumor response in lung cancer. In the present study, using Kras+/LSL-G12D; Trp53L/L (KP) mouse models of NSCLC, we identified cooperative effects between JQ1 and PD-1 antibody. The numbers of tumor-infiltrating Tregs were reduced and activation of tumor-infiltrating T cells, which had a T-helper type 1 (Th1) cytokine profile, was enhanced, underlying their improved effector function. Furthermore, lung tumor–bearing mice treated with this combination showed robust and long-lasting antitumor responses compared with either agent alone, culminating in substantial improvement in the overall survival of treated mice. Thus, combining BET bromodomain inhibition with immune checkpoint blockade offers a promising therapeutic approach for solid malignancies such as lung adenocarcinoma. Cancer Immunol Res; 6(10); 1234–45. ©2018 AACR.

Small-cell lung cancer (SCLC) has the highest malignancy among all lung cancers, exhibiting aggressive growth and early metastasis to distant sites. For 30 years, treatment options for SCLC have been limited to chemotherapy, warranting the need for more effective treatments. Frequent inactivation of TP53 and RB1 as well as histone dysmodifications in SCLC suggest that transcriptional and epigenetic regulations play a major role in SCLC disease evolution. Here we performed a synthetic lethal screen using the BET inhibitor JQ1 and an shRNA library targeting 550 epigenetic genes in treatment-refractory SCLC xenograft models and identified HDAC6 as a synthetic lethal target in combination with JQ1. Combined treatment of human and mouse SCLC cell line–derived xenograft tumors with the HDAC6 inhibitor ricolinostat (ACY-1215) and JQ1 demonstrated significant inhibition of tumor growth; this effect was abolished upon depletion of NK cells, suggesting that these innate immune lymphoid cells play a role in SCLC tumor treatment response. Collectively, these findings suggest a potential new treatment for recurrent SCLC. Significance: These findings identify a novel therapeutic strategy for SCLC using a combination of HDAC6 and BET inhibitors. Cancer Res; 78(13); 3709–17. ©2018 AACR.

Although most activating mutations of epidermal growth factor receptor (EGFR)-mutant non-small cell lung cancers (NSCLCs) are sensitive to available EGFR tyrosine kinase inhibitors (TKIs), a subset with alterations in exon 20 of EGFR and HER2 are intrinsically resistant and lack an effective therapy. We used in silico, in vitro, and in vivo testing to model structural alterations induced by exon 20 mutations and to identify effective inhibitors. 3D modeling indicated alterations restricted the size of the drug-binding pocket, limiting the binding of large, rigid inhibitors. We found that poziotinib, owing to its small size and flexibility, can circumvent these steric changes and is a potent inhibitor of the most common EGFR and HER2 exon 20 mutants. Poziotinib demonstrated greater activity than approved EGFR TKIs in vitro and in patient-derived xenograft models of EGFR or HER2 exon 20 mutant NSCLC and in genetically engineered mouse models of NSCLC. In a phase 2 trial, the first 11 patients with NSCLC with EGFR exon 20 mutations receiving poziotinib had a confirmed objective response rate of 64%. These data identify poziotinib as a potent, clinically active inhibitor of EGFR and HER2 exon 20 mutations and illuminate the molecular features of TKIs that may circumvent steric changes induced by these mutations.

Background: KRAS glycine-to-cysteine amino acid substitutions at codon 12 (KRASG12C) occur in ~13% of non-small cell lung cancers (NSCLC), ~3% of colorectal cancers (CRC), and less commonly in other cancer types. In early phase clinical trials of patients with KRASG12C-mutant cancers, promising antitumor activity has been reported with drugs such as adagrasib (MRTX849) and sotorasib (AMG510) which are direct inhibitors of KRASG12C. These small molecule irreversible inhibitors bind covalently to cysteine 12 within the switch II pocket which is formed, in part, by residues H95, Y96, and Q99. Mechanisms of acquired resistance to these therapies are currently unknown. Methods: Patients with KRASG12C-mutant NSCLC and CRC who were enrolled on adagrasib clinical trials and developed subsequent disease progression were included in this study if they were also consented to institutional review board-approved correlative studies at participating institutions. Tissue biopsies were analyzed histologically; tumor and/or circulating tumor DNA samples underwent next generation sequencing at the time of disease progression which was compared to that from pre-treatment samples when available. Results: A total of 30 patients were included in this study, 23 with NSCLC and 7 with CRC (25 with ctDNA, 7 with tissue sequencing, 2 with both). At the time of acquired resistance to adagrasib, we observed multiple on-target acquired KRAS alterations: mutations of the covalent-binding C12 residue, including C12W, C12F, C12V; a KRAS G13D mutation; high-level amplification of the KRASG12C allele; and mutation of the switch II binding pocket residues R68S, H95D, H95R, and Y96C. Furthermore, we detected several acquired off-target bypass mechanisms of resistance such as EGFR or MET amplification; activating mutations in NRAS (Q61K), BRAF (V600E), MAP2K1 (K57N, I99_K104del, E102_I103del), and RET (M918T); and oncogenic fusions involving RET, BRAF, RAF1, and FGFR. In two NSCLC cases with repeat tissue biopsies, histologic transformation from lung adenocarcinoma to squamous cell carcinoma was observed with no identifiable genomic mechanism of acquired resistance. In several cases, multiple coincident resistance mechanisms were identified in the same patient. Deep scanning mutagenesis studies were performed in parallel and identified the landscape of resistance mutations to adagrasib and sotorasib. While most resistance mutations confer high-level resistance to both therapies, some second-site mutations display differential sensitivity to distinct KRASG12C inhibitors, suggesting potential therapeutic strategies for overcoming drug resistance to specific mutations. Conclusion: Diverse genomic and histologic mechanisms impart resistance to covalent KRASG12C inhibitors in patients with cancer. Acquired genomic mutations, amplifications, and rearrangements may be potentially targetable by combining KRASG12C inhibition with available kinase inhibitors or SHP2 inhibitors. Citation Format: Mark Awad, Shengwu Liu, Kathryn Arbour, Viola Zhu, Melissa Johnson, Rebecca Heist, Tejas Patil, Gregory Riely, Joseph Jacobson, Julien Dilly, Xiaoping Yang, Nicole Persky, David Root, Lynette Sholl, Lee Lim, Kavita Garg, Mark Li, Lars Engstrom, Laura Waters, J. David Lawson, Peter Olson, James Christensen, Piro Lito, Sai-Hong Inatius Ou, Pasi Janne, Andrew Aguirre. Mechanisms of acquired resistance to KRAS G12C inhibition in cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB002.

Purpose: KRAS-activating mutations are the most common oncogenic driver in non–small cell lung cancer (NSCLC), but efforts to directly target mutant KRAS have proved a formidable challenge. Therefore, multitargeted therapy may offer a plausible strategy to effectively treat KRAS-driven NSCLCs. Here, we evaluate the efficacy and mechanistic rationale for combining mTOR and WEE1 inhibition as a potential therapy for lung cancers harboring KRAS mutations. Experimental Design: We investigated the synergistic effect of combining mTOR and WEE1 inhibitors on cell viability, apoptosis, and DNA damage repair response using a panel of human KRAS-mutant and wild type NSCLC cell lines and patient-derived xenograft cell lines. Murine autochthonous and human transplant models were used to test the therapeutic efficacy and pharmacodynamic effects of dual treatment. Results: We demonstrate that combined inhibition of mTOR and WEE1 induced potent synergistic cytotoxic effects selectively in KRAS-mutant NSCLC cell lines, delayed human tumor xenograft growth and caused tumor regression in a murine lung adenocarcinoma model. Mechanistically, we show that inhibition of mTOR potentiates WEE1 inhibition by abrogating compensatory activation of DNA repair, exacerbating DNA damage in KRAS-mutant NSCLC, and that this effect is due in part to reduction in cyclin D1. Conclusions: These findings demonstrate that compromised DNA repair underlies the observed potent synergy of WEE1 and mTOR inhibition and support clinical evaluation of this dual therapy for patients with KRAS-mutant lung cancers. Clin Cancer Res; 23(22); 6993–7005. ©2017 AACR.

Cancer stem cells (CSCs) are considered one of the key contributors to chemoresistance and tumor recurrence. Therefore, the precise identification of reliable CSC markers and clarification of the intracellular signaling involved in CSCs remains a great challenge in fields relating to cancer biology. Here, we implemented a novel chemoresistant prostate cancer patient-derived xenograft (PDX) model in NOD/SCID mice and identified CD54 as a candidate gene among the most highly enriched gene expression profiles in prostate tumors exposed to chronic cisplatin administration. Additional in vitro and in vivo assays showed that CD54 played a critical role in the self-renewal and tumorigenesis of prostate CSCs. Moreover, silencing CD54 greatly reduced the tumorigenesis of prostate cancers both in vitro and in vivo and significantly extended the survival time of tumor-bearing mice in a prostate cancer xenograft model. Dissection of the molecular mechanism revealed that the p38-Notch1 axis was the main downstream signaling pathway in CD54-mediated regulation of CSCs in prostate cancers. Together, these results established that CD54 could be a novel reliable prostate CSC marker and provided a new potential therapeutic target in prostate cancer via CD54-Notch1 signaling.

PURPOSE: Evaluating drug responses using primary patient derived cells ex vivo represents a potentially rapid and efficient approach to screening for new treatment approaches. Here, we sought to identify neratinib combinations in HER2 mutant non-small cell lung cancer (NSCLC) patient xenograft derived organotypic spheroids (XDOTS) using a short term ex vivo system. METHODS: We generated two HER2 mutant NSCLC PDX models (DFCI359 (HER2 exon19 755_757LREdelinsRP) and DFCI315 (HER2 exon20 V777_G778insGSP)) and used the PDX tumors to generate XDOTS. Tumor spheroids were grown in a microfluidic device and treated ex vivo with neratinib based drug combinations. Live/dead quantification was performed by dual labeling deconvolution fluorescence microscopy. The most efficacious ex vivo combination was subsequently validated in vivo using the DFCI359 and DFCI315 PDXs and a HER2(YVMA) genetically engineered mouse model (GEMM). RESULTS: Both neratinib and afatinib, but not gefitinib, induced cell death in DFCI359 XDOTS. The combinations of neratinib/trastuzumab, and neratinib/temsirolimus enhanced the therapeutic benefit of neratinib alone in DFCI315 and DFCI359. The combination of neratinib and trastuzumab in vivo was more effective compared to single agent neratinib or trastuzumab and was associated with more robust inhibition of HER2 and downstream signaling. CONCLUSIONS: The XDOTS platform can be used to evaluate therapies and therapeutic combinations ex vivo using PDX tumors. This approach may accelerate the identification and clinical development of therapies for targets with no or few existing models and/or therapies.

Purpose: Despite the challenge to directly target mutant KRAS due to its high GTP affinity, some agents are under development against downstream signaling pathways, such as MEK inhibitors. However, it remains controversial whether MEK inhibitors can boost current chemotherapy in KRAS-mutant lung tumors in clinic. Considering the genomic heterogeneity among patients with lung cancer, it is valuable to test potential therapeutics in KRAS mutation–driven mouse models. Experimental Design: We first compared the pERK1/2 level in lung cancer samples with different KRAS substitutions and generated a new genetically engineered mouse model whose tumor was driven by KRASG12C, the most common KRAS mutation in lung cancer. Next, we evaluated the efficacy of selumetinib or its combination with chemotherapy, in KRASG12C tumors compared with KRASG12D tumors. Moreover, we generated KRASG12C/p53R270H model to explore the role of a dominant negative p53 mutation detected in patients in responsiveness to MEK inhibition. Results: We determined higher pERK1/2 in KRASG12C lung tumors compared with KRASG12D. Using mouse models, we further identified that KRASG12C tumors are significantly more sensitive to selumetinib compared with KrasG12D tumors. MEK inhibition significantly increased chemotherapeutic efficacy and progression-free survival of KRASG12C mice. Interestingly, p53 co-mutation rendered KRASG12C lung tumors less sensitive to combination treatment with selumetinib and chemotherapy. Conclusions: Our data demonstrate that unique KRAS mutations and concurrent mutations in tumor-suppressor genes are important factors for lung tumor responses to MEK inhibitor. Our preclinical study supports further clinical evaluation of combined MEK inhibition and chemotherapy for lung cancer patients harboring KRASG12C and wild-type p53 status. Clin Cancer Res; 24(19); 4854–64. ©2018 AACR.

KRAS mutation is present in approximately 30% of human lung adenocarcinomas. Although recent advances in targeted therapy have shown great promise, effective targeting of KRAS remains elusive, and concurrent alterations in tumor suppressors render KRAS-mutant tumors even more resistant to existing therapies. Contributing to the refractoriness of KRAS-mutant tumors are immunosuppressive mechanisms, such as increased presence of suppressive regulatory T cells (Tregs) in tumors and elevated expression of the inhibitory receptor PD-1 on tumor-infiltrating T cells. Treatment with BET bromodomain inhibitors is beneficial for hematologic malignancies, and they have Treg-disruptive effects in a non-small cell lung cancer (NSCLC) model. Targeting PD-1 inhibitory signals through PD-1 antibody blockade also has substantial therapeutic impact in lung cancer, although these outcomes are limited to a minority of patients. We hypothesized that the BET bromodomain inhibitor JQ1 would synergize with PD-1 blockade to promote a robust antitumor response in lung cancer. In the present study, using Kras(+/LSL-G12D); Trp53(L/L) (KP) mouse models of NSCLC, we identified cooperative effects between JQ1 and PD-1 antibody. The numbers of tumor-infiltrating Tregs were reduced and activation of tumor-infiltrating T cells, which had a T-helper type 1 (Th1) cytokine profile, was enhanced, underlying their improved effector function. Furthermore, lung tumor–bearing mice treated with this combination showed robust and long-lasting antitumor responses compared to either agent alone, culminating in substantial improvement in the overall survival of treated mice. Thus, combining BET bromodomain inhibition with immune checkpoint blockade offers a promising therapeutic approach for solid malignancies such as lung adenocarcinoma.

Purpose: HER2 (or ERBB2) aberrations, including both amplification and mutations, have been classified as oncogenic drivers that contribute to 2% to 6% of lung adenocarcinomas. HER2 amplification is also an important mechanism for acquired resistance to EGFR tyrosine kinase inhibitors (TKI). However, due to limited preclinical studies and clinical trials, currently there is still no available standard of care for lung cancer patients with HER2 aberrations. To fulfill the clinical need for targeting HER2 in patients with non–small cell lung cancer (NSCLC), we performed a comprehensive preclinical study to evaluate the efficacy of a third-generation TKI, osimertinib (AZD9291). Experimental Design: Three genetically modified mouse models (GEMM) mimicking individual HER2 alterations in NSCLC were generated, and osimertinib was tested for its efficacy against these HER2 aberrations in vivo. Results: Osimertinib treatment showed robust efficacy in HER2wt overexpression and EGFR del19/HER2 models, but not in HER2 exon 20 insertion tumors. Interestingly, we further identified that combined treatment with osimertinib and the BET inhibitor JQ1 significantly increased the response rate in HER2-mutant NSCLC, whereas JQ1 single treatment did not show efficacy. Conclusions: Overall, our data indicated robust antitumor efficacy of osimertinib against multiple HER2 aberrations in lung cancer, either as a single agent or in combination with JQ1. Our study provides a strong rationale for future clinical trials using osimertinib either alone or in combination with epigenetic drugs to target aberrant HER2 in patients with NSCLC. Clin Cancer Res; 24(11); 2594–604. ©2018 AACR. See related commentary by Cappuzzo and Landi, p. 2470

The bromodomain and extraterminal (BET) family of proteins comprises four members-BRD2, BRD3, BRD4 and the testis-specific isoform BRDT-that largely function as transcriptional coactivators and play critical roles in various cellular processes, including the cell cycle, apoptosis, migration and invasion. BET proteins enhance the oncogenic functions of major cancer drivers by elevating the expression of these drivers, such as c-Myc in leukemia, or by promoting the transcriptional activities of oncogenic factors, such as AR and ERG in prostate cancer. Pathologically, BET proteins are frequently overexpressed and are clinically linked to various types of human cancer; they are therefore being pursued as attractive therapeutic targets for selective inhibition in patients with cancer. To this end, a number of bromodomain inhibitors, including JQ1 and I-BET, have been developed and have shown promising outcomes in early clinical trials. Although resistance to BET inhibitors has been documented in preclinical models, the molecular mechanisms underlying acquired resistance are largely unknown. Here we report that cullin-3SPOP earmarks BET proteins, including BRD2, BRD3 and BRD4, for ubiquitination-mediated degradation. Pathologically, prostate cancer-associated SPOP mutants fail to interact with and promote the degradation of BET proteins, leading to their elevated abundance in SPOP-mutant prostate cancer. As a result, prostate cancer cell lines and organoids derived from individuals harboring SPOP mutations are more resistant to BET-inhibitor-induced cell growth arrest and apoptosis. Therefore, our results elucidate the tumor-suppressor role of SPOP in prostate cancer in which it acts as a negative regulator of BET protein stability and also provide a molecular mechanism for resistance to BET inhibitors in individuals with prostate cancer bearing SPOP mutations.

Cardiac fibroblasts (CFs) phenotypic conversion to myofibroblasts (MFs) represents a crucial event in cardiac fibrosis that leads to impaired cardiac function. However, regulation of this phenotypic transformation remains unclear. Here, we showed that sirtuin-7 (Sirt7) plays an important role in the regulation of MFs differentiation. Sirt7 expression and phosphorylation were upregulated in CFs upon angiotensin-II (Ang-II) stimulation. Sirt7 depletion by siRNA in CFs resulted in decreased cell proliferation and extracellular matrix (ECM) deposition. Further, examination of Sirt7-depleted CFs demonstrated significantly lower expression of α-smooth muscle actin (α-SMA), the classical marker of MFs differentiation, and decreased formation of focal adhesions. Moreover, overexpression of Sirt7 increased α-SMA expression in Ang-II treated CFs and exacerbated Ang-II-induced MFs differentiation. Moreover, Sirt7 depletion could largely reverse Ang-II induced increase of nuclear translocalization and activity of smad2 and extracellular regulated kinases (ERK) in CFs. Importantly, the increased differentiation of CFs to MFs was also abolished by smad2 siRNA or U0126. Our findings reveal a novel role of Sirt7 and its phosphorylation in the phenotypic conversion of CFs to MFs and might lead to the development of new therapeutic and prognostic tools for cardiac fibrosis.

Natural killer (NK) cell activation is well orchestrated by a wide array of NK cell receptor repertoire. T-cell immunoglobulin and ITIM domain (TIGIT) receptor was recently defined as an inhibitory receptor that is expressed on NK cells and T cells. TIGIT receptor/poliovirus receptor (PVR) ligand engagement signaling inhibits cytotoxicity mediated by NK and CD8(+) T cells. However, it is unclear how TIGIT/PVR signaling regulates cytokine secretion in NK cells. Here we show that TIGIT/PVR engagement suppresses interferon-γ (IFN-γ) production of NK cells. TIGIT transgenic NK cells generate less IFN-γ undergoing TIGIT/PVR ligation. Moreover, TIGIT knock-out NK cells produce much more IFN-γ. TIGIT/PVR ligation signaling mediates suppression of IFN-γ production via the NF-κB pathway. We identified a novel adaptor β-arrestin 2 that associates with phosphorylated TIGIT for further recruitment of SHIP1 (SH2-containing inositol phosphatase 1) through the ITT-like motif. Importantly, SHIP1, but not other phosphatases, impairs the TNF receptor-associated factor 6 (TRAF6) autoubiquitination to abolish NF-κB activation, leading to suppression of IFN-γ production in NK cells.

The granzyme/perforin pathway is a major mechanism for cytotoxic lymphocytes to eliminate virus-infected and tumor cells. The balance between activation and inhibition of the proteolytic cascade must be tightly controlled to avoid self damage. Granzyme H (GzmH) is constitutively expressed in NK cells and induces target cell death; however, how GzmH activity is regulated remains elusive. We reported earlier the crystal structures of inactive D102N-GzmH alone and in complex with its synthetic substrate and inhibitor, as well as defined the mechanisms of substrate recognition and enzymatic activation. In this study, we identified SERPINB1 as a potent intracellular inhibitor for GzmH. Upon cleavage of the reactive center loop at Phe343, SERPINB1 forms an SDS-stable covalent complex with GzmH. SERPINB1 overexpression suppresses GzmH- or LAK cell–mediated cytotoxicity. We determined the crystal structures of active GzmH and SERPINB1 (LM-DD mutant) in the native conformation to 3.0- and 2.9-Å resolution, respectively. Molecular modeling reveals the possible conformational changes in GzmH for the suicide inhibition. Our findings provide new insights into the inhibitory mechanism of SERPINB1 against human GzmH.

Effective therapies for non–small cell lung cancer (NSCLC) remain challenging despite an increasingly comprehensive understanding of somatically altered oncogenic pathways. It is now clear that therapeutic agents with potential to impact the tumor immune microenvironment potentiate immune-orchestrated therapeutic benefit. Herein, we evaluated the immunoregulatory properties of histone deacetylase (HDAC) and bromodomain inhibitors, two classes of drugs that modulate the epigenome, with a focus on key cell subsets that are engaged in an immune response. By evaluating human peripheral blood and NSCLC tumors, we show that the selective HDAC6 inhibitor ricolinostat promotes phenotypic changes that support enhanced T-cell activation and improved function of antigen-presenting cells. The bromodomain inhibitor JQ1 attenuated CD4+FOXP3+ T regulatory cell suppressive function and synergized with ricolinostat to facilitate immune-mediated tumor growth arrest, leading to prolonged survival of mice with lung adenocarcinomas. Collectively, our findings highlight the immunomodulatory effects of two epigenetic modifiers that, together, promote T cell–mediated antitumor immunity and demonstrate their therapeutic potential for treatment of NSCLC.Significance: Selective inhibition of HDACs and bromodomain proteins modulates tumor-associated immune cells in a manner that favors improved T-cell function and reduced inhibitory cellular mechanisms. These effects facilitated robust antitumor responses in tumor-bearing mice, demonstrating the therapeutic potential of combining these epigenetic modulators for the treatment of NSCLC. Cancer Discov; 7(8); 852–67. ©2017 AACR.This article is highlighted in the In This Issue feature, p. 783

Skin is a highly immunogenic site for vaccine delivery due to its richness of antigen-presenting cells. Several vaccines have been approved for skin delivery and in particular intradermal delivery in the last two decades. Yet intradermal delivery often causes frequent and severe local reactions, preventing the incorporation of adjuvants to further boost skin vaccination. Here we describe a novel skin delivery technology, called micro-fractional epidermal powder delivery or EPD, with minimized local reactions for improved skin vaccination. EPD is based on laser or microneedle treatment to generate microchannel arrays in the epidermis followed by topical application of powder vaccine-coated array patches to deliver vaccines into the skin via microchannels. Due to the fractional delivery, EPD significantly reduces vaccine/adjuvant-induced local reactions without compromising vaccine immunogenicity and adjuvant potency. EPD also eliminates needle injection-associated pain and is promising to improve vaccine stability due to the direct powder delivery. This chapter describes detailed methods for the advantageous EPD in preclinical animal models.