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Background: Oncogenic alterations (gene amplification, mutation, and fusion/rearrangements) of fibroblast growth factor receptor 2 (FGFR2) are rare and occur at varying frequencies across solid tumor types and have become critical therapeutic targets in drug development. First generation FGFR pan-kinase inhibitors non-selectively inhibit FGFR1-4 and are associated with dose limiting toxicities and narrow therapeutic windows. Off-isoform toxicity (FGFR1-hyperphosphatemia; FGFR4-diarrhea) and on-target acquired resistance have led to limited efficacy, which is primarily seen in FGFR2-fusion+ intrahepatic cholangiocarcinoma. Therapies that selectively target FGFR2 remain an unmet need in advanced breast cancer as well as other solid tumor types. RLY-4008 is a novel, oral FGFR2 inhibitor designed to overcome the limitations of pan-FGFR inhibitors (FGFRi) by potently and selectively targeting primary oncogenic FGFR2 alterations and acquired resistance mutations. RLY-4008 is > 200-fold selective over FGFR1, > 80- and > 5000-fold selective over FGFR3 and FGFR4 respectively. Here we describe a phase 1/2 study to investigate the safety and antitumor activity in advanced FGFR2 altered cancers, including breast cancer. Methods: ReFocus is a phase 1/2 open label global study evaluating the safety and efficacy of RLY-4008 (NCT04526106) in adult patients with advanced unresectable and/or metastatic cancers harboring an FGFR2 alteration. Key eligibility criteria include: documented FGFR2 alteration in blood or tissue per local assessment, ECOG performance status of 0-1, disease that is refractory or not adequately responding to standard therapy, has no available standard therapy, or patient is intolerant of, or declined standard therapy (including pan-FGFRi), and measurable or evaluable disease per RECIST 1.1. FGFR2 alteration will be confirmed retrospectively by central laboratory assessment. Part 1 dose escalation employed the Bayesian Optimal Interval (BOIN) design to determine the MTD/RP2D of RLY-4008. Part 2 dose expansion is presently enrolling patients at the RP2D of RLY-4008 and includes 5 cohorts comprised of patients with: 1. FGFR2 fusion+ cholangiocarcinoma previously treated with an FGFRi; 2. FGFR2 fusion+ cholangiocarcinoma not previously treated with an FGFRi; 3. FGFR2 fusion+ solid tumors; 4. FGFR2 mutation+ solid tumors and 5. FGFR2 amplified solid tumors. Solid tumors in cohorts 3, 4 and 5 will have a focus in breast cancer. The primary endpoint is objective response rate (ORR); key secondary endpoints include: duration of response, safety and tolerability, correlation of FGFR2 genotype by central tissue assessment with antitumor response, characterization of PK profile, and quality of life. US enrollment began September 2020 and has expanded into Europe and Asia. Clinical trial information: NCT04526106. Citation Format: Suneel Kamath, David Tai, Irene Moreno, Hani Babiker, Zhaohui Jin, Changhoon Yoo, Fabien Ricard, Kai Yu Jen, Jim Coward, Jia Liu, Frans Opdam, Michael Millward, Mariano Ponz-Sarvise, Jeffrey Yachnin, Richard Kim, Joon Oh Park, Vivek Subbiah, Alison M. Schram. ReFocus: A Phase 1/2 Study of the Highly Selective FGFR2 Inhibitor, RLY-4008, in Patients with Advanced Solid Tumors Including Breast Cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT3-24-01.

Background: Targeting constitutively active mutant kinases with selective small molecule inhibitors is a key therapeutic pillar of precision oncology. Phosphatidylinositol-4,5bisphosphate-3 kinase, catalytic subunit alpha (PIK3CA) mutations leading to oncogenic activation of PI3Kα represent the largest opportunity for this approach in solid tumors. However, there is no selective inhibitor that targets mutant PI3Kα in the clinic. Toxicity related to non-selective inhibition of WT PI3Kα (hyperglycemia) and other PI3K isoforms limits the tolerability, dosing and efficacy of the orthosteric inhibitor, alpelisib, the only approved solid tumor PI3K inhibitor. RLY-2608, a novel oral allosteric PI3Kα inhibitor, is uniquely designed to overcome these limitations via mutant- and isoform-selective PI3Kα inhibition for greater target coverage, improved tolerability and antitumor activity. We initiated a first-in-human (FIH), study to evaluate the clinical activity of RLY-2608 as a single agent in advanced solid tumor patients (pts) with PI3KCA mutations and in combination with fulvestrant in pts with PIK3CA mutant, HR+, HER2- metastatic breast cancer (MBC). Methods: This is a global, multi-center, dose escalation/expansion study (NCT05216432) of RLY2608 as a single agent in adults who have advanced solid tumors and are refractory, intolerant, or declined standard therapy and RLY-2608 in combination with fulvestrant in previously treated pts with HR+/HER2- MBC. Eligibility criteria include presence of PI3KCA mutation (blood or tumor) per local assessment, ECOG performance status 0-1, measurable or evaluable disease per RECIST 1.1 and no prior PI3K inhibitor (except combination group 2). RLY-2608 is administered on a continuous schedule with 4-week cycles. Adverse events (AEs) per CTCAE v5, PK, biomarkers (mutant ctDNAs and insulin pathway markers) and anti-tumor activity are assessed serially. Dose escalation employs a Bayesian Optimal Interval design to identify MTD and RP2D. Following dose escalation, pts will be treated with RLY-2608 at the MTD/RP2D in a monotherapy dose expansion with 5 groups (N=75, 15 each): 1. Clear cell ovarian carcinoma 2. Head and neck squamous cell carcinoma 3. Cervical cancer 4. Other solid tumors 5. PI3KCA double mutations. In addition, two expansion cohorts will enroll patients with HR+/HER2- MBC treated with RLY-2608 and fulvestrant combination (N = 30, 15 each): 1. No prior PI3K therapy 2. Intolerant to PI3K inhibitors. The primary endpoints are MTD/RP2D and AE profile for single agent and combination; key secondary endpoints are PI3KCA genotype in blood and tumor, PK, biomarkers, and overall response rate. US enrollment began December 2021 and ex-USA startup is under way. Citation Format: Andreas Varkaris, Erika Hamilton, Jason Henry, Alexander I. Spira, Alison M. Schram, Julia E. McGuinness, Gege Tan, Xiaoyan Li, Tamieka Hunter, Ramin Samadani, Alison Timm, Djuro Karanovic, Vivek Subbiah, Cesar A. Perez. First-in-human global multi-center study of RLY-2608, a pan mutant and isoform selective PI3Kα inhibitor, as a single agent in advanced solid tumor patients and in combination with fulvestrant in patients with advanced breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT3-22-01.

Introduction: Preclinical studies suggest cooperativity between blocking the human epidermal growth factor receptor 2 (HER2) and the vascular endothelial growth factor (VEGF) pathways in gastroesophageal adenocarcinomas (GEAs). Methods:Patients with previously untreated advanced HER2 positive GEAs were treated with standard of care chemotherapy capecitabine 1,200 mg/m2 days 1-14 and oxaliplatin 130 mg/m2 day 1 (CAPOX) plus trastuzumab 6 mg/kg day 1, once every 3 weeks. Investigational agent bevacizumab (7.5 mg/kg, VEGF mAb) was added on day 1 of each cycle for all patients. The primary endpoint was radiographic objective response rate by RECIST 1.1. ctDNA was extracted and profiled from serially banked plasma samples (every other treatment cycle) using CLIA certified 152-gene next generation sequencing (NGS) panel assay, PredicineCARETM. Results:Sixty one patients were screened for the study of whom 24 were ineligible. Thirty-seven patients were enrolled, and one withdrew consent prior to starting. Thirty-six patients were evaluable for efficacy and safety. The median follow-up was 23.2 months (IQR: 11.0 - 46.9 months). All enrolled patients are now off study. Radiographic objective response rate was 81%. Median progression-free survival (PFS) and overall survival (OS) were 14.0 months (95% CI, 11.3 -36.4) and 23.2 months (95% CI, 16.6-36.4), respectively. The most common grade 3-4 toxicities were diarrhea, peripheral neuropathy, and hypertension. Baseline ctDNA profiling identified HER2 amplifications in 76.7% of tested cases (23/30). Baseline ctDNA based tumor fraction (TF) was highly prognostic and TF > 50th centile had a statistically significantly worse PFS of 11.3 months (95% CI 5.2-18) vs. 22.7 months (95% CI 18.1-NA), p value = 0.0013, and OS of 15.4 months (95% CI 8.0-27.6) vs. 28.0 months (95% CI 17.8-NA), p value = 0.022. 56.7% of cases (17/30) had alternative MAPK drivers present in pretreatment ctDNA, most commonly amplifications in EGFR, FGFR1, MET, and KRAS. Additional MAPK alterations were associated with worse PFS of 12.5 months (95% CI 5.2-NA) vs. 22.7 months (95% CI 8.5-NA), p-value = 0.0067, and OS of 16.5 months (95% CI 8.0-27.6) vs. 32.3 months (95% CI 17.8-NA), p-value = 0.015. 19 cases had plasma profiled at time of clinical resistance of whom 10 showed new oncogenic mutations not detectable in the matched baseline sample. These included mutations in MAPK pathway (KRAS, NRAS, BRAF, HER2; n = 1 each) and PI3K pathway (PTEN, PIK3CA; n = 1 each), suggesting a role in therapeutic resistance. Conclusions:The combination of CAPOX, trastuzumab and bevacizumab shows striking clinical activity comparable to novel triplet regimens that include PD1 blockade for HER2+ GEAs. Further evaluation of VEGF mAb in combination with chemoimmunotherapy and anti-PD1 regimens is warranted. Diagnostic ctDNA profiling identifies cases with high TF and alternative MAPK drivers who have worse outcomes. Serial measurement of ctDNA may allow early identification of novel genetic resistance mechanisms which can aid attempts at early intervention. Citation Format: Harshabad Singh, Kristen E. Lowder, Kevin Kapner, Ronan J. Kelly, Hui Zheng, Nadine J. McCleary, Thomas A. Abrams, Jennifer A. Chan, Eileen M. Regan, Samuel J. Klempner, Alison M. Hannigan, Lauren K. Brais, Elizabeth A. Andrews, Matthew B. Yurgelun, James M. Cleary, Douglas A. Rubinson, Lauren L. Ritterhouse, Garrett E. Maron, Andrew J. Aguirre, Lu Tan, Pan Du, Jeffrey A. Meyerhardt, Emma Gardecki, Jochen K. Lennerz, Shidong Jia, Brian M. Wolpin, Peter C. Enzinger. Long term results and ctDNA correlatives for CAPOX BETR: A multi-center phase II trial of capecitabine, oxaliplatin, bevacizumab and trastuzumab for previously untreated HER2 positive metastatic gastroesophageal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT155.

Background: BGB-3245 is a RAF dimer inhibitor with preclinical activity in MAPK-altered tumor models harboring BRAF V600 mutations, atypical BRAF mutations/fusions, and RAS mutations. This study is investigating the safety, pharmacokinetics, and preliminary antitumor activity of BGB-3245 in patients (pts) with advanced or refractory MAPK-altered solid tumors. Methods: Eligible pts were ≥18 yrs old with ECOG 0-1 and had solid tumors harboring MAPK pathway alterations. Dose-escalation and cohort-size decisions were made using the Modified Toxicity Probability Interval Design. The starting dose was 5 mg QD. Treatment emergent adverse events (TEAEs) were graded per NCI CTCAE v5.0. Tumor responses were assessed by investigators using RECIST v1.1. Results: As of 1 Sep 2022, 42 pts were treated across 6 cohorts (5-60 mg QD). The median age was 60 yrs; pts had received a median of 3 prior lines of treatment. All pts had TEAEs; 79% had treatment-related (TR) AEs. The most common TRAEs (≥ 10%) were rash acneiform (33%), rash maculopapular (24%), fever (17%), ALT elevations and nausea (both 12%). Gr ≥3 TRAEs were reported in 29% of pts, events in ≥ 2 pts included decreased platelet count and rash maculopapular (3 each), ALT and AST elevations, and fever (2 each). Dose reductions occurred in 5 pts: rhabdomyolysis (1), LVEF decreased (1), hand-foot syndrome (1), rash maculopapular (1), and liver function abnormalities (1). Dose interruptions due to AEs occurred in 60% of pts. Dose discontinuations occurred in 79% of pts, 57% due to disease progression or death, 21% due to AE. Dose limiting toxicities were observed at 10 mg, 40 mg, and 60 mg. 40 mg QD was determined as the MTD. PK results showed generally dose-proportional increases in exposure. Tmax was at ~2 h; BGB-3245 had a long terminal half-life and 7.4-fold average accumulation in exposure at steady-state. 79% of pts were efficacy evaluable. The disease control rate was 48% with 1 CR, 5 cPR, 2 uPR and 8 SD≥24 wks. Objective responders included BRAF V600E melanoma pts post-BRAF/MEK and checkpoint inhibitors (2; 1 CR, 1 cPR), 1 NRAS G12S melanoma and 1 NRAS Q61K melanoma (post checkpoint inhibitors), 1 BRAF V600E LGSOC (progressed on BRAF inhibitor), 1 BRAF V600E cholangiocarcinoma (progressed on BRAF/MEK inhibitors), 1 BRAF K601E/PIK3CA endometrial cancer, and 1 KRAS G12D appendiceal cancer. Preliminary analysis of circulating tumor DNA showed correspondence to clinical response. Conclusions: BGB-3245 has a manageable safety profile and a generally dose-proportional PK. Antitumor activity was observed in pts with no approved targeted therapy options. The safety and early efficacy profile of BGB-3245 supports further investigation in selected MAPK-altered tumors. Citation Format: Alison M. Schram, Vivek Subbiah, Ryan Sullivan, Rasha Cosman, Jia Liu, Eric I. Sbar, Thuy Hoang, Jiarong Chen, Mark Johnson, Vincent Amoruccio, Todd Shearer, Adeela Kamal, Jocelyn Lewis, Wenlin Shao, Badreddin Edris, Lusong Luo, Jayesh Desai. A first-in-human, phase 1a/1b, open-label, dose-escalation and expansion study to investigate the safety, pharmacokinetics, and antitumor activity of the RAF dimer inhibitor BGB-3245 in patients with advanced or refractory tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT031.

Introduction: Neoadjuvant chemoimmunotherapy is promising in improving outcomes for patients with resectable lung cancer in the phase III setting, though data are immature at this time for overall survival (OS). Here, we present outcomes after 3 years of follow-up from the first reported study of neoadjuvant immunotherapy + chemotherapy in this population. Methods: This open-label, multi-center single-arm investigator-initiated phase II study was conducted at three hospitals in the USA. Neoadjuvant atezolizumab, carboplatin, and nab-paclitaxel were administered for up to 4 cycles prior to surgical resection. The primary endpoint of major pathologic response (MPR) has been previously reported; here we report mature disease-free survival (DFS) and OS as well as clinical characteristics of patients with recurrent brain metastases (BM) with integrated data from tumor genomics, gene expression, and quantitative immunofluorescent (QIF) measurement of immune markers. Results: Of 30 enrolled patients, 29 were taken to the operating room with 26 completing successful R0 resection. 17 patients experienced MPR, of whom 10 had pathological complete response (pCR). The median follow-up time was 39.5 months (95% CI: 30.9-49.4). Median OS was 55.8 months (95% CI: 43.6-NA); median DFS was 34.5 months (95% CI: 18.4-NA). Landmark OS at 12, 24, and 36 months were 97%, 80%, and 77%, respectively; DFS: 80%, 60%, and 49%. Radiographic and pathologic measures of response, as well as baseline PD-L1 levels, did not statistically significantly associate with DFS or OS. The strongest trends were observed with pCR (OS: HR 0.22, 95% CI 0.03-1.83; DFS: HR 0.45, 95% CI 0.12-1.65). Percent decrease of radiographic response correlated inversely with percent pathological regression (Pearson correlation -0.44, 95% CI: -0.71—-0.08). Of 14 patients evaluable for site of recurrence, 6 developed BM. 5/6 patients with BM died, with median time to recurrence of 12.4 months (95% CI: 9.9-32.6) and time to death of 45.3 months (95% CI: 22.7-55.8). 3/6 patients who developed BM experienced MPR (2 achieved pCR). Radiographic response and PD-L1 level did not significantly associate with development of BM. Patients whose tumors had mutations in STK11 and KEAP1 did not experience statistically worse DFS/OS, though incidence of BM trended higher. Reduced copy number of STK11 and KEAP1, which both reside on chromosome 19p, was observed in about 1/3 of tumors. Deletion of either gene was significantly associated with worse pathologic response, lower levels of PD-L1+ cells by QIF, and BM. Conclusions: Mature OS data reveal sustained clinical benefit of neoadjuvant chemoimmunotherapy with atezolizumab. Predictivity of radiographic and pathologic surrogates for survival was limited. Further study is warranted to establish the associations between STK11 and KEAP1 genomic alterations and key clinical outcomes in early-stage NSCLC. Citation Format: Brian S. Henick, Justin F. Gainor, Mark M. Awad, Codruta Chiuzan, Stephanie Izard, Yohanna Georgis, Peter D. Koch, Robert F. Garofano, Cheryl V. Wong, Anjali Saqi, Jessica M. Grindheim, Katja Schulze, Naiyer A. Rizvi, Benjamin Izar, Alison M. Taylor, Catherine A. Shu. 3-year update of neoadjuvant atezolizumab + chemotherapy in patients with resectable non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT217.

Background: NRG1 fusions represent a rare and potentially actionable oncogenic alteration found in ~0.2% of solid tumors. Seribantumab is a fully human anti-HER3 IgG2 monoclonal antibody that blocks aberrant NRG1 fusion protein binding to HER3 thereby preventing ligand-dependent activation and dimerization resulting in complete inhibition of the PI3K/AKT and MAPK downstream signaling pathways. Seribantumab has shown significant anti-tumor activity in PDX models and in patients (pts) with solid tumors harboring NRG1 fusions. Methods: CRESTONE (NCT04383210) is a phase 2 study of seribantumab in adult pts with solid tumors harboring NRG1 fusions who received at least one prior therapy and were naïve to ERBB-targeted therapy (Cohort 1); pts previously treated with ERBB-targeted therapies (exploratory Cohort 2) and pts with tumors harboring additional molecular alterations (exploratory Cohort 3). Here, we present updated efficacy results for pts in Cohort 1 dosed at 3 g IV QW. Safety data are evaluated for pts enrolled in Cohort 1 and exploratory Cohorts 2 and 3. Results: As of Dec 2, 2022, 51 pts were enrolled across all cohorts with 30 pts in Cohort 1 dosed at 3 g IV QW. Median age was 62 years (range 19-84); median prior lines of therapy was 2 (range 1-7); tumor types included non-small cell lung cancer (NSCLC, n=30), pancreatic adenocarcinoma (PDAC, n=6), biliary tract/cholangiocarcinoma (CCA, n=6), breast (n=4), and others (n=5); 15 different NRG1 fusion partners were identified with CD74 (22%) and SLC3A2 (16%) as the most frequently reported. In the overall safety population, 41 pts (80%) reported at least one treatment-related adverse event (TRAE). The most common TRAEs (occurring in ≥20% of pts) were diarrhea (41%), fatigue (29%), rash (24%), and nausea (22%). Four pts (8%) experienced Gr 3/4 TRAEs; no Gr 5 TRAEs. The safety profile for Cohort 1 was similar to the overall safety population. Among the 30 pts in Cohort 1, 22 were evaluable for investigator assessed (INV) response per RECIST v1.1; 2 pts (9%) had confirmed complete response (CR), 6 pts (27%) had confirmed partial response (PR), and 13 pts (59%) had stable disease (SD) as their best overall response (BOR). The INV objective response rate (ORR, confirmed PR + CR) was 36% and disease control rate (DCR, confirmed PR+CR+SD) was 95%. The overall duration of response ranged from 1.4 to 17.2 months. In pts with NSCLC, the INV-ORR was 39% and DCR was 94%. Conclusions: Seribantumab has an acceptable safety and tolerability profile as a single agent in pts with solid tumors harboring NRG1 fusions. Updated efficacy data indicate seribantumab has robust and durable clinical activity, including CRs, across different tumor types harboring an NRG1 fusion and is a promising treatment option. Citation Format: Tejas Patil, Daniel R. Carrizosa, Mark E. Burkard, Karen L. Reckamp, Jayesh Desai, Young Kwang Chae, Stephen V. Liu, Kartik Konduri, Shirish M. Gadgeel, Jessica J. Lin, Parneet K. Cheema, David R. Spigel, Alison M. Schram, Valerie M. Jansen, Yasir Y. Elamin. CRESTONE: A Phase 2 study of seribantumab in adult patients with neuregulin-1 (NRG1) fusion positive locally advanced or metastatic solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT229.

Squamous Cell Carcinoma (SCC) is an aggressive form of cancer that develops in the mucosal epithelium of the digestive and respiratory tracts as well as on the skin. Two major risk factors for development of SCC are carcinogen exposures, such as alcohol and tobacco, and Human Papillomavirus (HPV) infection. Viral- and carcinogen-driven SCCs have differential responses to radiation, chemotherapy, and immunotherapy, with HPV+ SCCs responding better to these treatments than HPV- carcinomas. Analysis of aneuploidy patterns of genomic samples from The Cancer Genome Atlas (TCGA) have shown that squamous cancers cluster together and are characterized by gain of chromosome arm 3q gain and loss of chromosome arm 3p. However, while HPV+ SCCs show similar rates of 3q gain, they have significantly lower rates of 3p loss, suggesting that 3p deletion and HPV infection might have overlapping roles in cancer initiation and/or progression. In addition, the degree to which these two paths of tumor development contribute to differences in disease progression and outcome has been largely unexplored. We have identified a strong correlation between 3p deletion and high epithelial-mesenchymal transition (EMT) gene signature across all cancer types. Interestingly, interferon signaling has been found to be upregulated in non-squamous cancers upon 3p deletion but downregulated in squamous cancers with 3p deletion. SCCs positive for HPV infection show decreased expression of EMT genes and increased expression of genes in interferon signaling and cell cycle checkpoint pathways. Together, the results of these TCGA analyses suggest mechanisms by which chromosome 3p deletion and HPV infection may affect cancer progression and are currently being validated in vitro in a panel of squamous cancer cell lines. Additionally, we will use a targeted CRISPR-Cas9 system developed in our lab to delete chromosome 3p, as well as transfect HPV oncoproteins, in normal keratinocytes to create isogenic models. With these models, we will study the role of individual aneuploidy events in tumorigenesis, tumor development, and metastasis in the context of HPV positive and negative SCC. Citation Format: Samyukta Mallick, Alison M. Taylor. The role of chromosome arm 3p and human papillomavirus on proliferation, differentiation, and metastasis in squamous cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1414.

Mammography screening is widely used for earlier detection of breast cancer and has been shown to contribute to reduction of mortality and morbidity. Most screen-detected breast cancers are early stage, hormonal receptor-positive, HER2-negative (HR+ HER2-) breast cancers. The majority of HR+ HER2- cancers are assigned to molecular intrinsic subtypes of Luminal A and Luminal B, which generally harbour low recurrence risk, with Luminal B cases being more invasive but still less aggressive than HER2-enriched or Basal-like subtypes. However, some of these Luminal cancers later recur (5+ years after diagnosis) often as advanced and/or metastatic disease. We studied a cohort of screen-detected breast cancers (42 cases) at Sunnybrook Health Sciences Centre (Toronto, ON Canada) with integrated cross-platform radiomics, molecular and proteomic analysis in an attempt to better characterise these cancers and their proclivity for late recurrence. Utilising a Nanostring 200-gene assay, the molecular subtypes (PAM50 and MammaTyper-like) and a range of recapitulated clinical prognostic scores (50-Gene, 70-Gene and 21-Gene Risk) were determined for these cancers. While a majority of cases (29 out of 42) were subtyped as Luminal A cancers by PAM50, a fraction (12 out of 29) of these were either subtyped as Luminal B/HER2+ based on MammaTyper-like results, or measured as intermediate to high risk of recurrence based on the 70-Gene or 21-Gene Risk classification. Although discordant results from multi-parametric assays are not uncommon, we postulate that here, discordance could suggest presence of heterogeneous cellular or molecular elements with invasive phenotype that could lead to aggressive transformations in the long run. Differential expression analysis between Luminal A cases with consistent subtyping and low risk prognostication and those with discordant subtyping or prognostication results revealed a panel of genes with significant changes in expression. Further analysis of RNA expression of these genes via Receiver Operating Characteristic (ROC) curve demonstrated that some genes showed high Area Under the Curve (AUC) scores in the classification between the two groups of Luminal A breast cancers, further supporting the existence of distinct molecular phenotypes. Targeted sequencing with Oncomine Comprehensive Assay V3 did not reveal particular mutational patterns between the two Luminal A groups. Nevertheless, radiomic analysis of mammographic images of the cancer, as well as single cell phenotyping of the tumor microenvironment with protein multiplexing will be incorporated to further characterise elements that are phenotypically different, and potentially identify mechanistic drivers contributing to late recurrence in Luminal A cancers. Citation Format: Alison M. Cheung, Dan Wang, Kela Liu, Yutaka Amemiya, Elzbieta Slodkowska, James G. Mainprize, Jane Bayani, Arun Seth, John Bartlett, Martin J. Yaffe. Integrative cross-platform characterisation of mammographic screen-detected breast cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5622.

Many translational studies suggest racial and ethnic survival disparities in lung squamous cell carcinoma (LSCC), with self-identified African-Americans showing significantly lower overall survival and progression-free survival than self-identified Caucasians. However, potential clinical and genomic factors contributing to this disparity have yet to be elucidated. Using clinically annotated genomic data from 501 LSCC tumor samples in the Cancer Genome Atlas (TCGA), we compared clinical data, gene expression profiles, mutations, and focal and arm-level copy number changes from tumors across ancestral groups to identify significantly differential events. Within this dataset, patients of AFR ancestry had worse survival and progression-free survival then patients of EUR ancestry. We applied the Cox Proportional Hazards model to predict overall and progression-free survival as functions of genetic ancestry alongside other genetic, molecular, and clinical variables. We found a significant difference in metastatic stage between tumors from patients of African (AFR) and European (EUR) ancestry, which was significant in predicting survival. Compared to tumors from EUR patients, tumors from AFR patients featured increased chromosome arm 8q gain and more frequent amplification of genetic locus chr8q24, which contains proto-oncogene MYC. Expression of MYC target genes was also significantly increased in AFR samples relative to EUR samples. These findings may suggest a role for the MYC pathway in differential cancer progression. We found more frequent amplification of genetic loci chr22q11 and chr16p11 in AFR samples compared to EUR samples. We identified top differentially mutated genes between groups, of which SPRR3, PDGFA, FRS3, and C21orf62 correlate with survival. We also found immune signaling gene sets enriched in the EUR group by gene set expression analysis (GSEA). These results suggest potential genetic and clinical factors implicated in racial survival disparities. Further studies and more diverse sampling of cancer patient populations are required to validate these differences and elucidate patient-specific treatment modalities. Citation Format: Sejal Jain, Alexandria G. Yao, Diane Allen-Gipson, Fatemeh Momen-Heravi, Alison M. Taylor. Clinical and genomic correlates with genetic ancestry in lung squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1947.

Activating KRAS mutations frequently occur in several cancers including the majority of pancreatic ductal adenocarcinoma (96%), ~50% of colorectal cancers, and ~30% of lung adenocarcinoma. It has been shown that mutant K-ras preferentially signals through RAF-MEK-ERK signaling and that blockade of this pathway is essential for tumor regression. However, targeted MEK inhibitors (MEKi) have shown limited clinical benefit in the treatment of K-ras mutant cancers due to resistance caused by the feedback activation of the upstream kinase CRAF. Recently, PROTACs (Proteolysis-Targeting Chimeras) targeting MEK1 and MEK2 were developed, providing a new therapeutic strategy to degrade MEK1/2 in K-ras mutant cancer cells. Due to the fact that feedback-induced CRAF causes MEKi resistance in K-ras mutant cells, we postulated that degrading MEK1/2 could bypass CRAF-mediated resistance. Indeed, treatment of MEKi-sensitive or resistant K-ras mutant cell lines with MEK1/2 degraders rapidly reduced MEK1/2 protein levels and downstream ERK signaling causing growth inhibition and apoptosis. Proteomics characterization of K-ras mutant cell lines following MEK1/2 degrader or inhibitor treatment revealed MEK1/2 degradation exhibited distinct signaling pathway responses compared to inhibition. Together, our studies showed MEK1/2 degraders represent a promising avenue for the treatment K-ras mutant cancers that can by-pass resistance mechanisms observed with traditional MEK1/2 inhibitors. Citation Format: Carlos Herrera-Montavez, Alison M. Kurimchak, Jian Jin, James S. Duncan. Characterizing MEK1/2 degradation in K-ras mutant cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2621.

INTRODUCTION/METHODS: The multistep process of the tumor invasion-metastasis cascade is a major barrier to effective therapy. Mutations of the tumor suppressor p53 are frequently detected in esophageal squamous cell carcinoma (ESCC) cases, which in turn correlate with high metastatic rates. To understand the mutant p53-mediated mechanisms in promoting ESCC metastasis, we conducted RNA-Seq, ChIP-Seq and cytokine array on isogenic primary and metastatic tumor cells harvested from our mouse model of esophageal cancer, L2-Cre; LSL-Trp53R172H; Rosa26LSL-YFP, in which we have identified macrophage colony stimulating factor 1 (CSF1) to be a direct gene target of p53-R172H. We have targeted CSF1/CSF1R signaling to assess its pro-tumorigenic roles. In addition to studying tumor intrinsic mechanisms, we have established multiplex immunofluorescence and flow cytometry approaches to characterize the changes in tumor microenvironment (TME). Overall, this study aims to investigate the role and mediators of CSF1 signaling through its cognate receptor CSF1R by which missense p53 mutations can promote lung metastasis. RESULTS/DISCUSSION: We demonstrate that metastatic ESCC has increased Csf1 expression compared to primary tumors and this is dependent upon p53 mutation status, which is reinforced by TCGA data and patient-derived tissue microarrays (TMAs). The TMA analysis also suggested that CSF1 expression is higher in tumors that are poorly differentiated. Furthermore, through the proximity ligation assay (PLA), we have identified that bromodomain and extra-terminal (BET) protein BRD4, which binds to acetylated histones to regulate transcription interacts with p53-R172H at higher levels compared to wild-type p53 to induce Csf1 expression. We show that the BRD4/CSF1/CSF1R signaling axis fosters tumor invasion, subcutaneous tumor growth and metastatic burden in lungs in a mutant p53 background. In accordance, targeting CSF1/CSF1R signaling reduces phosphorylation of STAT3 in the metastatic tumors, which suggests a mechanism for increased invasiveness and metastasis. In parallel, upon inhibiting this axis, we have identified decreased infiltration of F4/80+CD163+ and F4/80+CD206+ M2-polarized macrophages, as well as CD31+ endothelial cells, and increased number of CD3+CD8+ cytotoxic T-cells at the metastatic tumor sites, indicating that the CSF1/CSF1R pathway plays a critical role in shaping the pro-metastatic and immunosuppressive TME. Finally, analysis of squamous cell carcinoma (SCC) datasets reveals that specific p53 mutations are associated with differential survival rates and CSF1 expression. CONCLUSION: We have demonstrated novel roles and mechanisms of mutant p53-dependent CSF1-CSF1R signaling pathway in fostering ESCC tumor invasion and lung metastasis that may be applicable to other SCCs. We believe this can open up new avenues for therapeutic applications. Citation Format: Gizem Efe, Katherine M. Cunningham, Qiaosi Tang, Kensuke Sugiura, Karen Dunbar, Kensuke Suzuki, Lois Resnick-Silverman, Alison M. Taylor, James J. Manfredi, Carol L. Prives, Anil K. Rustgi. The role of mutant p53-mediated mechanisms in modulating the tumor microenvironment and promoting lung metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1289.

Intrahepatic cholangiocarcinoma (ICC) is an aggressive malignancy of the bile ducts within the liver characterized by high levels of genetic heterogeneity. In the context of such genetic variability, determining which oncogenic mutations drive ICC growth has been difficult, and developing modes of patient stratification and targeted therapies remains challenging. Here we model the interactions between rare mutations with more common driver genes and combine in silico analysis of patient data with highly multiplexed in vivo CRISPR-spCas9 screens to perform a functional in vivo study into the role genetic heterogeneity plays in driving ICC. Novel tumor suppressors were uncovered, which, when lost, cooperate with the RAS oncoprotein to drive ICC growth. Focusing on a set of driver mutations that interact with KRAS to initiate aggressive, sarcomatoid-type ICC revealed that tumor growth relies on Wnt and PI3K signaling. Pharmacologic coinhibition of Wnt and PI3K in vivo impeded ICC growth regardless of mutational profile. Therefore, Wnt and PI3K activity should be considered as a signature by which patients can be stratified for treatment independent of tumor genotype, and inhibitors of these pathways should be levied to treat ICC. Significance: This work shows that, despite significant genetic heterogeneity, intrahepatic cholangiocarcinoma relies on a limited number of signaling pathways to grow, suggesting common therapeutic vulnerabilities across patients.

Background: Loss of function in the tumor suppressor gene, PTEN, activates PI3K/AKT signaling, driving tumor growth. Somatic mutations in PTEN occur in 5-10% of estrogen-receptor-positive (ER+) breast cancer (BC), and PTEN loss/inactivation is associated with an aggressive BC phenotype and poor outcome. Capivasertib, a pan-AKT kinase inhibitor, has shown antitumor activity in solid tumors. In ER+ BC, suppression of PI3K/AKT signaling results in a compensatory increase in ER-dependent transcription, potentially limiting the efficacy of AKT inhibitors when given as monotherapy. We therefore investigated concurrent inhibition of AKT and ER with combination therapy of capivasertib and fulvestrant in PTEN-mutant ER+ metastatic BC (MBC). Methods: In an expansion cohort (part F) of a Phase I study (NCT01226316), oral capivasertib 400 mg twice daily, 4 days on 3 days off, and fulvestrant at labeled dose, was administered to ER+ MBC patients (pts) with tumors harboring a deleterious PTEN alteration (identified in tissue/plasma by local next-generation sequencing [NGS], with central NGS and immunohistochemistry [IHC] performed retrospectively). Pts were enrolled in fulvestrant-naïve (FN) or fulvestrant-resistant (FR) cohorts (max 24 pts/cohort). Key objectives included safety and efficacy based on 24-week clinical benefit rate (CBR). Results: At data cut-off, 31 pts (12 FN; 19 FR) received treatment. Median number of prior metastatic regimens was 7. FN pts had higher rates of visceral disease (100%) and prior chemotherapy receipt (median 4 [range 0-8]) than FR pts (84%; median 2 [1-7]), respectively]. CBR and median progression-free survival (PFS) were 17% and 2.6 months in FN pts, and 37% and 4.1 months in FR pts, respectively (Table). Twenty-four patients (77%) had PTEN mutations and 7 (23%) had PTEN gene deletions determined by local NGS. Central plasma NGS confirmed 79% (19/24) of the PTEN mutations, and IHC confirmed complete loss of the PTENprotein in 85% (22/26) of cases. Treatment-related grade ≥3 adverse events (AEs) occurred in 32%, most frequently diarrhea and maculopapular rash (both n=2 pts). Treatment-related AEs resulted in dose reduction in 2 pts. Table. Clinical efficacyFN, n=12FR, n=19ORR, % (95% CI)8 (0.2, 39)21 (6, 46)CBR, % (95% CI)17 (2, 48)37 (16, 62)Confirmed response, n (%)1 (8)4 (21)Stable disease ≥24 weeks, n (%)2 (17)3 (16)Median PFS, months (95% CI)2.6 (1.2–4.2)4.1 (1.5–6.7)Median duration of response, months (95% CI)5.5 (NC–NC)6.9 (1.4–NC)Data cut-off was 21 March 2019. Median time from last fulvestrant administration to study entry in FR pts (n=19) was 13.8 months (range 0.7–28.2). CBR was defined as confirmed responders and those with stable disease ≥24 weeks. NC, not calculable (because of limited pt numbers); ORR, objective response rate Conclusions: Capivasertib plus fulvestrant is clinically active in heavily pretreated PTEN-mutated ER+ MBC, including in pts with prior resistance to fulvestrant. Efficacy appeared marginally better in FR than FN pts, possibly due to enrichment of pts with more aggressive disease in the FN cohort. Further analyses of the relationship between genomic features, such as concurrent mutations with drug activity, will be reported. Citation Format: Lillian M Smyth, Gerald Batist, Funda Meric-Bernstam, Peter Kabos, Iben Spanggaard, Ana Lluch, Alison Schram, Andrea Varga, Andrea Wong, Helen Ambrose, Alan Barnicle, T. Hedley Carr, Elza C de Bruin, Carolina Salinas-Souza, Andrew Foxley, Joana Hauser, Justin PO Lindemann, Rhiannon Maudsley, Robert McEwen, Michele Moschetta, Martine Roudier, Gaia Schiavon, Pedram Razavi, Udai Banerji, Sarat Chandarlapaty, José Baselga, David M Hyman. Capivasertib (AZD5363) in combination with fulvestrant in PTEN-mutant ER+ metastatic breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-19-05.

Dysregulation of PI3K signaling is a common event in human cancer, but feedback inhibition of receptor kinase signaling and/or induction of PTEN translation by activated PI3K/AKT/mTOR signaling reduces pathway output and tumor dependency. In some cancers, including the majority of endometrial carcinomas, these lesions coexist and cause synergistic hyperactivation of pathway output, particularly mTORC1 kinase signaling. Although this suggests that PI3K signaling is a driver of these endometrial cancers, standard inhibitors have had only marginal activity in patients with advanced disease. We here show that, in experimental isogenic models and PDX models with PI3K and PTEN alterations, PI3K inhibitors and rapalogs are weak inhibitors of TORC1 targets and slow but do not suppress the in vivo growth of these tumors. Revolution Medicines has developed a series of bi-steric selective and potent mTORC1 inhibitors that inhibit the phosphorylation of 4EBP-1, S6K and other mTORC1 substrates at concentrations that do not affect TORC2 substrates and thus do not induce the hyperglycemia caused by downregulation of AKT signaling by pan-mTOR kinase inhibitors. We have explored the biologic and anti-tumor effects of these inhibitors in models of endometrial cancer with coexistent PI3K mutation and PTEN inactivation. The mTORC1 kinase selective bi-steric inhibitor RMC-6272 can potently suppress both mTORC1 activity and the growth of these tumor cells in vitro. Moreover, in contrast to PI3K inhibition, RMC-6272 effectively inhibited the phosphorylation of mTORC1 kinase substrates and completely suppressed the growth in vivo of multiple PDXs with this genotype without inducing hyperglycemia or causing weight loss in the mice. The results suggest that dysregulation of TORC1 activity is an important driver of endometrial carcinomas with coexistent PTEN inactivation and PI3K mutations and that selective TORC1 kinase inhibitors may prove to be useful therapeutics in this context. The bi-steric mTORC1 kinase inhibitor RMC-5552 is the first clinical candidate of this class and clinical testing is ongoing (NCT04774952). Citation Format: Hilla Solomon, Radha Mukherjee, Xiaoping Chen, HuiYong Zhao, Elisa de Stanchina, Britta Weigelt, Alison M. Schram, Carol Aghajanian, Mallika Singh, Jan Smith, Neal Rosen. Effective in vivo treatment of endometrial tumor models with coexistent mutant PI3K and PTEN inactivation with a selective bi-steric mTORC1 kinase inhibitor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB089.

Background: Cholesterol reduction is considered a mechanism through which lipid-lowering drugs including statins are associated with a reduced aggressive prostate cancer risk. While prior cohort studies found positive associations of total cholesterol with advanced stage and grade in White men based mostly on cholesterol at baseline, whether associations for total cholesterol, low (LDL)- and high (HDL)-density lipoprotein cholesterol, apolipoprotein B (LDL particle component) and A1 (HDL particle component), and triglycerides exist for fatal prostate cancer and in Black men using time-updated biomarkers is unknown. Methods: We conducted a prospective study of 1,553 Black and 5,071 White cancer-free men attending visit 1 (1987-1989) of the Atherosclerosis Risk in Communities Study. Death from prostate cancer was ascertained from the underlying cause on death certificates. Follow-up began at visit 1 and ended at date of death, loss to follow-up, or 12/31/2018, which ever came first. There were 128 deaths from prostate cancer (43 in Black men, 85 in White men) ascertained over 153,184 person years of follow-up (mean 23 years). We estimated multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CI) for fatal prostate cancer per 1-standard deviation increment and for tertiles (T1-T3) of time-updated lipid biomarkers adjusting for baseline age, education, race and field center, and updated BMI, waist circumference, smoking status, hyperglycemia and diagnosed diabetes, aspirin use, and lipid-lowering drug use overall, and in Black and White men. Results: Higher total cholesterol concentration was associated with higher fatal prostate cancer risk in White men only (HR per-1 SD=1.25; 95%CI=1.00-1.58), and higher concentration of LDL cholesterol appeared to be associated with fatal prostate cancer in White men only (HR per-1 SD=1.26; 95%CI=0.99-1.60). Apolipoprotein B was non-linearly associated with fatal prostate cancer overall (T2 vs. T1 HR=1.66; 95% CI=1.05-2.64) and in Black men (T2 vs. T1 HR=3.59; 95% CI=1.53-8.40) but not in White men (T2 vs. T1 HR=1.13; 95% CI=0.65-1.97). HRs were >1 overall (T3 vs. T1 HR=1.18) and in Black men (T3 vs. T1 HR=2.11) but were not statistically significant. HDL-cholesterol, Apolipoprotein A1 and triglycerides were not associated with fatal prostate cancer overall and by race. Tests for statistical interaction by race were not statistically significant. Conclusion: Positive associations with fatal prostate cancer were observed with total and LDL-cholesterol in White men, and apolipoprotein B in Black men. These findings may improve the understanding of lipid metabolism in prostate carcinogenesis, and further emphasize the importance of cholesterol control. Support: NHLBI contracts, NCI grants, NPCR Citation Format: Michael T. Marrone, Anna E. Prizment, David Couper, Kenneth R. Butler, Brad C. Astor, Corinne E. Joshu, Elizabeth A. Platz, Alison M. Mondul. Total, LDL-, HDL-cholesterol, apolipoproteins, and triglycerides and risk fatal prostate cancer in black and white men in the ARIC study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB158.

Cervical cancer screening rates among Arab-American women have been consistently shown to be lower than that of non-Hispanic White and Black women in the state of Michigan. Addressing the low cervical cancer screening rates among Arab American women in Michigan requires a deep understanding of the community’s perspective about cervical cancer screening. Thus, we conducted a series of focus groups in Southeastern Michigan to understand the attitudes, acceptability, and barriers of cervical cancer screening among this population. Four focus groups with a total of 19 women were conducted via Zoom. Participants were recruited through social media channels and community organizations. All focus groups were conducted with self-identifying Arab, Arab American, or Chaldean women aged 30 to 61. The focus groups were conducted in either English, Arabic, or a mixture of both languages. Women completed a brief anchoring survey with demographic questions and a self-assessment of their HPV knowledge (see Table 1). The guided discussion centered around knowledge of cervical cancer, broadly, knowledge of Human papillomavirus (HPV) and its transmission, attitudes towards the HPV vaccination, and attitudes towards cervical cancer screening, which included HPV self-sampling methods. The recorded sessions were transcribed and are being coded using Dedoose Version 8.0.35, a qualitative analysis software. During the focus group, the discussion centered around barriers at the individual and community levels for screening and vaccination, attitudes towards preventive health care including screening, a need for accessible women’s health literature, and health education. The women also discussed vaccine hesitancy related to HPV and COVID19. This suggests the need for targeted community interventions. General characteristics of participants (N*=19) N Mean Age (N=17) 37.9 8.7 (SD) Married (N=18) 11 61.1% Survey Language Arabic 6 31.6% English 13 68.4% How well would you say the financial needs are met in your household? Just sufficient 9 50% More than sufficiently met 3 16.7% Barely making it 3 16.7% Not met at all 3 16.7% How well informed do you think you are about cervical cancer? Not informed at all 1 5.6% Not well informed 10 55.6% Moderately informed 5 27.8% Well informed 1 5.6% Very well informed 1 5.6% Have you had vaginal sex (intercourse) before? Yes 15 83.3% No 3 16.7% Have you had oral sex before? Yes 8 47.1% No 9 52.9% Do you have any children? Yes 15 83.3% No 3 16.7% *Complete data available for 17 participants, partially complete data for 2 participants, and missing data for 1 participant Citation Format: Lilah Khoja, Heidi G. Torres, Mariam Ayyash, Madiha Tariq, Alison M. Mondul, Rafael Meza, Celeste L. Pearce. Cervical cancer screening and vaccination acceptability and attitudes amongst Arab American women in southeastern Michigan [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2211.

Invasive Ductal Carcinoma (IDC) and Invasive Lobular Carcinoma (ILC) are two major subtypes of breast cancer with significant differences in their histological and molecular underpinnings. ILC has a unique loss of E-cadherin (CDH1) which we have previously demonstrated as a negative regulator of the Insulin-like Growth Factor 1 receptor (IGF1R) through a comprehensive analysis of cell line models and tumor samples. We propose that loss of E-cadherin in ILC sensitizes cells to growth factor signaling and thus alters their sensitivity to growth factor signaling inhibitors. To investigate this, we used CRISPR to generate CDH1 knockout (KO) IDC cell lines (MCF7, T47D, ZR75.1) to uncover the mechanism by which E-cadherin loss activates the IGF pathway while also assessing its targetability. CDH1 KO cells exhibited anchorage independent growth in suspension culture and altered p120 catenin localization as observed in ILC tumors. Through in vitro studies, we show increased signaling sensitivity to IGF/insulin ligands and enhanced signaling duration in CDH1 KO cells. In addition, we observed a higher migratory potential of CDH1 KO cells compared to wild type (WT) cells, which was further enhanced as a chemotactic response to IGF1 or serum. Further, this phenotype could be reversed with an IGF1R inhibitor, BMS-754807. We additionally identified an increase in Collagen I haptotaxis in the CDH1 KO cells, which was also translated into a novel invasive phenotype towards serum in the T47D CDH1 KO cells. Despite no significant differences in membranous IGF1R levels between WT and CDH1 KO cells, higher ligand-receptor interaction was observed with CDH1 KO cells, demonstrating an increased ligand-receptor complex formation upon stimulation. Our results suggest that loss of CDH1 results in an increase in IGF1 receptor availability for ligand binding which in turn allows for an enhanced downstream signaling activation. Interestingly, a physical repression of E-cadherin on IGF1R could not be demonstrated, suggesting spatial changes on the membrane following E-cadherin loss may control ligand binding. Critically, increased sensitivity to IGF1R, PI3K, AKT and MEK inhibitors was observed in CDH1 KO cells suggesting that these targets should be further explored in ILC and that CDH1 loss may be exploited as a biomarker of response, or for patient stratification to inhibitors targeting these pathways. Citation Format: Ashuvinee Elangovan, Laura Savariau, Megan E. Yates, Jagmohan Hooda, Alison M. Nagle, Steffi Oesterreich, Jennifer M. Atkinson, Adrian V. Lee. Loss of E-cadherin induces IGF1R activation revealing a targetable pathway in invasive lobular breast carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2690.

MicroRNAs (miR) are evolutionarily highly conserved non-coding RNAs that play roles in fundamental cellular functions by post-translational gene regulation. In cancer pathogenesis, miRs exert both anti-tumorigenic and pro-tumorigenic effects by virtue of miR-specific and context-dependent mechanisms. The role of chromosomal changes and mutation status on miR expression in cancer remains unknown. Here we provide evidence that chromosome arm 1p loss and P53 mutations are associated with lower levels of miR-34a, particularly in squamous cancers such as head and neck squamous cell carcinoma (HNSCC). miR-34a acts as a tumor suppressor and physically interacts with and functionally targets the proto-oncogene MET, and modulates cell proliferation. miR-34a expression is inversely correlated with MET in tumor tissue. We found that miR-34a suppresses HNSCC carcinogenesis, at least in part, by downregulating MET, consequently inhibiting HNSCC proliferation. Moreover, ectopic expression of miR-34a reduces HNSCC cell proliferation and tumor burden in vitro and in vivo, represses expression of genes and proteins involved in epithelial-mesenchymal transition, and negates the oncogenic effect of MET in mouse tumors. Our work demonstrates a role of miR-34a in maintaining tumor immunity, as overexpression of miR-34a resulted in a decease in percentage of anti-inflammatory (M2-like) TAMs and PDL1+TAMs, which are reported to have pro-tumorigenic activity. In HNSCC patient samples, higher levels of miR-34a are significantly associated with a higher frequency of Th1 cells, myeloid cells, and regulatory T cells. Our results demonstrate that miR-34a directly targets MET and maintains anti-tumor immune activity, and could potentially represent a new therapeutic approach for HNSCC. Citation Format: Xun Wu, Yi-Shing Lisa Cheng, Methew Matthen, Angela Yoon, Gary Schwartz, Shashi Bala, Alison M. Taylor, Fatemeh Momen-Heravi. Role of miR-34a-MET axis in head and neck cancer squamous cell carcinoma [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 2367.

Epidemiological data identifies disparities in black patients for head and neck squamous carcinoma (HNSCC) screening, detection, treatment, and survival. Although socioeconomic and environmental factors play a role in the existing racial disparities, HNSCC incidence and survival rates in the black population cannot be attributed to these factors alone. To investigate the role race plays in the genomics of head and neck cancer, we examined HNSCC samples from 49 black and 446 white patients in the Cancer Genome Atlas (TCGA). We used computationally-derived ancestry identifications to correlate race with HNSCC molecular features. We then characterized the extent to which genomic alterations in black patients impact their clinical outcomes. We found that black patients lived significantly fewer disease-free months and had a poorer overall survival than white patients. Black patients showed a higher frequency of human papillomavirus (HPV)-negative than HPV-positive tumors compared to white patients. Black patients were found to suffer higher rates of metastasis and more aggressive lymph node involvement. Differences in patient primary tumor site were also identified, with black patients having a higher prevalence of tumors in the larynx and lower prevalence of tumors in the tongue compared to white patients. We also found higher frequencies of RUNX1T1, KMT2D, and UNC13C mutations and lower frequency of PIK3CA mutations in black patients. We found a significant enrichment of MYC signaling and amplifications in the tumors of black patients compared to white patients. Novel data uncovered by this project brings us closer to understanding the racial disparities in HNSCC, and advances research aimed at eliminating those disparities. Unique tumor mutations and molecular signatures show promising clinical utility in providing more targeted, individualized screening diagnostic, and treatment modalities to reduce outcome disparities in the black population. Citation Format: Nadia Mezghani, Alexandria G. Yao, Alison M. Taylor, Fatemeh Momen-Heravi. Molecular subtypes of head and neck cancer in patients with African ancestry [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 2205.