Identification of acquired Notch3 dependency in metastatic Head and Neck Cancer

During cancer development, tumor cells acquire changes that enable them to invade surrounding tissues and seed metastasis at distant sites. These changes contribute to the aggressiveness of metastatic cancer and interfere with success of therapy. Our comprehensive analysis of "matched" pairs of HNSCC lines derived from primary tumors and corresponding metastatic sites identified several components of Notch3 signaling that are differentially expressed and/or altered in metastatic lines and confer a dependency on this pathway. These components were also shown to be differentially expressed between early and late stages of tumors in a TMA constructed from over 200 HNSCC patients. Finally, we show that suppression of Notch3 improves survival in mice in both subcutaneous and orthotopic models of metastatic HNSCC. Novel treatments targeting components of this pathway may prove effective in targeting metastatic HNSCC cells alone or in combination with conventional therapies.

Genomic analysis of early-stage lung cancer reveals a role for TP53 mutations in distant metastasis

Patients with non-small cell lung cancer (NSCLC) who have distant metastases have a poor prognosis. To determine which genomic factors of the primary tumor are associated with metastasis, we analyzed data from 759 patients originally diagnosed with stage I-III NSCLC as part of the AACR Project GENIE Biopharma Collaborative consortium. We found that TP53 mutations were significantly associated with the development of new distant metastases. TP53 mutations were also more prevalent in patients with a history of smoking, suggesting that these patients may be at increased risk for distant metastasis. Our results suggest that additional investigation of the optimal management of patients with early-stage NSCLC harboring TP53 mutations at diagnosis is warranted in light of their higher likelihood of developing new distant metastases.

Abstract 2311: Identification of therapeutic targets in HNSCC

HNSCC is 6th most common malignancy in the world. Despite advances in diagnosis and treatment, the survival rates remain low due in large part to metastatic disease. The underlying biology associated with metastatic disease and poor outcome in HNSCC remains unclear. Importantly, metastatic cells acquire new properties that permit them to invade surrounding tissues and seed metastasis at distant sites. While these acquired properties contribute to aggressiveness of metastatic cancer, they can be exploited to target metastatic cells selectively, sparing toxicity in normal tissues. We used functional genomic technologies to identify new therapeutic targets for advanced disease in HNSCC. These targets were identified by conducting whole genome shRNA screens in matched sets of cell lines derived from primary HNSCC tumors and their respective metastatic sites/recurrences. Since hypoxia is an important attribute of aggressive and therapy resistant subpopulations of HNSCC tumor cells, we also aimed to identify genes that became essential when cells are exposed to hypoxia. To complement the data from the functional screens and to further characterize our cell line collection, we utilized several high through put approaches including mutational analysis, proteomics and gene expression profiling. Moreover, we performed chemical screens using libraries of over 4000 FDA approved drugs with the aim to combine our functional genomic data with the results from the drug screens to discover drug/gene “hit” combinations that would provide a basis for development of novel anti-cancer therapies.While HNSCC derived cell lines represent a valuable tool to study this disease, their biology might not always accurately represent the biology of the tumors they were derived from. Therefore, we looked at the expression of the components of several key pathways that we discovered using the in vitro characterization in a patient material from over HNSCC surgical samples constructed into a TMA. Five of the hits belonged to the Notch signalling pathway and 4 others came from the proteomic analysis as they showed higher levels of surface expression in metastatic cells and/or under hypoxic conditions. Interestingly, higher proportion of patients with late stages of HNSCC belonged to the high Jag2 and Hey1 populations as compared to patients with low stages of HNSCC that mostly expressed low or intermediate levels of these proteins. This data is in line with our observations that Jag2 and Hey1 expression is elevated in cells derived from metastatic sites and is low in cells derived from primary tumors. Proportion of cells with high CD66 and TRAIL proteins was also higher among the late stage tumors suggesting that these biomarkers are of interest for further investigation. We discovered several molecular pathways that are important in metastatic/hypoxic HNSCC. We are investigating our ability to target these pathways using FDA approved drugs in order to achieve durable cures.

Citation Format: Maria Kondratyev, Aleksandra Pesic, Anna Dvorkin-Sheva, Troy Ketela, Natalie Stickle, Laurie Aiiles, Reidar Grenman, Marianne Koritzinsky, Brad Wouters. Identification of therapeutic targets in HNSCC [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 2311.

The Prevent Ovarian Cancer Program (POCP): Identification of women at risk for ovarian cancer using complementary recruitment approaches

BACKGROUND

Up to 20% of high-grade serous ovarian carcinomas (HGSOC) are hereditary; however, historical uptake of genetic testing is low. We used a unique combination of approaches to identify women in Ontario, Canada, with a first-degree relative (FDR) who died from HGSOC without prior genetic testing, and offer them multi-gene panel testing.

METHODS

From May 2015-Sept 2019, genetic counseling and testing was provided to eligible participants. Two recruitment strategies were employed, including self-identification in response to an outreach campaign and direct targeting of FDRs of deceased HGSOC patients treated at our institution. The rate of pathogenic variants (PV) in established/potential ovarian cancer risk genes and the benefits/challenges of each approach were assessed.

RESULTS

A total of 564 women enrolled in response to our outreach campaign (n = 473) or direct recruitment (n = 91). Mean age at consent was 52 years and 96% did not meet provincial testing criteria. Genetic results were provided to 528 individuals from 458 families. The rate of PVs in ovarian cancer risk genes was highest when FDRs were diagnosed with HGSOC <60 years (9.4% vs. 3.9% ≥ 60y, p = 0.0160). Participants in the outreach vs. direct recruitment cohort had a similar rate of PVs; however, uptake of genetic testing (97% vs. 89%; p = 0.0036) and study completion (95% vs. 87%; p = 0.0062) rates were higher in the former. Eleven participants with pathogenic variants have completed risk-reducing gynecologic surgery, with one stage I HGSOC and two breast cancers identified.

CONCLUSION

Overall PV rates in this large cohort were lower than expected; however, we provide evidence that genetic testing criteria in Ontario should include individuals with a deceased FDR diagnosed with HGSOC <60 years of age.

Tumor and germline next generation sequencing in high grade serous cancer: experience from a large population-based testing program

The aim of this study was to determine the prevalence of somatic and germline pathogenic variants (PVs) in high‐grade serous cancer (HGSC) and to demonstrate the technical feasibility and effectiveness of a large‐scale, population‐based tumor testing program. It involved a retrospective review of genetic test results in 600 consecutive HGSC tumor samples and a subsequent comparison of germline and tumor results in a subset of 200 individuals. Tumor testing was successful in 95% of samples (570/600) with at least one BRCA1/2 PV identified in 16% (93/570) of cases. Among the 200 paired cases, BRCA1/2 PVs were detected in 38 tumors (19%); 58% were somatic (22/38); and 42% were germline (16/38). There was 100% concordance between germline and tumor test results. This is the largest series of BRCA1/2 testing in HGSC (tumor‐only and paired cohorts), reported to date, and our data show that an effectively designed and validated population‐based tumor testing program can be used to determine both treatment eligibility and hereditary cancer risk.

Inter-laboratory proficiency testing scheme for tumour next-generation sequencing in Ontario: a pilot study

Background

A pilot inter-laboratory proficiency scheme for 5 Ontario clinical laboratories testing tumour samples for the Ontario-wide Cancer Targeted Nucleic Acid Evaluation (octane) study was undertaken to assess proficiency in the identification and reporting of next-generation sequencing (ngs) test results in solid tumour testing from archival formalin-fixed, paraffin-embedded (ffpe) tissue.

Methods

One laboratory served as the reference centre and provided samples to 4 participating laboratories. An analyte-based approach was applied: each participating laboratory received 10 ffpe tissue specimens profiled at the reference centre, with tumour site and histology provided. Laboratories performed testing per their standard ngs tumour test protocols. Items returned for assessment included genes and variants that would be typically reported in routine clinical testing and variant call format (vcf) files to allow for assessment of ngs technical quality.

Results

Two main aspects were assessed:■ Technical quality and accuracy of identification of exonic variants■ Site-specific reporting practicesTechnical assessment included evaluation of exonic variant identification, quality assessment of the vcf files to evaluate base calling, variant allele frequency, and depth of coverage for all exonic variants. Concordance at 100% was observed from all sites in the technical identification of 98 exonic variants across the 10 cases. Variability between laboratories in the choice of variants considered clinically reportable was significant. Of the 38 variants reported as clinically relevant by at least 1 site, only 3 variants were concordantly reported by all participating centres as clinically relevant.

Conclusions

Although excellent technical concordance for ngs tumour profiling was observed across participating institutions, differences in the reporting of clinically relevant variants were observed, highlighting reporting as a gap where consensus on the part of Ontario laboratories is needed.

Abstract 3054: Cell surface targets in head and neck cancer

HNSCC is 6th most common malignancy in the world. Despite advances in diagnosis and treatment, the survival rates remain low due in large part to metastatic disease. The underlying biology associated with metastatic disease and poor outcome in HNSCC remains unclear. Importantly, metastatic cells acquire new properties that permit them to invade surrounding tissues and seed metastasis at distant sites. While these acquired properties contribute to aggressiveness of metastatic cancer and interfere with success of therapies, they can also potentially be exploited to target metastatic cells selectively, sparing toxicity in normal tissues. We used functional genomic technologies to identify new potential therapeutic targets for advanced disease in HNSCC. These targets were identified by conducting whole genome shRNA screens in matched sets of cell lines derived from primary tumors and their respective metastatic sites, with the goal of identifying genes that become essential for cell survival only following metastasis. Since hypoxia is an important attribute of aggressive and therapy resistant subpopulations of HNSCC tumor cells, we also aimed to identify genes that became essential when cells are exposed to hypoxia. We are particularly interested in the identification of contextual synthetic lethal oncogenes expressed on the cell surface, as those are easily targetable by therapeutic antibodies. To identify these targets, we performed high-throughput flow cytometry screening that enables evaluation of 370 validated cell surface antibodies. Cell surface targets differentially expressed in metastatic lines included CECAM and CCR6 that were previously reported to be implicated in metastasis and tumor progression as well as Thy1, a known marker of stem cells involved in regulation of cell adhesion. Cell surface targets induced under hypoxic conditions across the cell lines included CA9, an enzyme that is known to regulate pH in hypoxic cells and be associated with tumor progression, as well as CD338, CD264 and CD312, that were previously associated with stemness in a few models of cancer. Interestingly, the described proteins were also found to be differentially essential in the shRNA screens, highlighting their functional importance in tumor progression and hypoxia survival. We are currently investigating the role of these proteins in HNSCC metastasis utilizing our unique collection of matched pairs of HNSCC lines from multiple patients. Moreover, we are utilizing our pipeline of patient derived HNSCC xenografts to test the effect of knocking down the described genes in patient tumors. We are also testing the expression of selected hits in histological sections of patient tumorsthe 400-patient TMA by immunohistochemistry looking for correlation with tumor grade, aggressiveness, levels of hypoxia as well as presence/absence of metastasis in the patient.

Citation Format: Maria Kondratyev, Aleksandra Pesic, Azin Sayad, Troy Ketela, Natalie Stickle, Carl Virtanen, Jason Moffat, Laurie Ailles, Marianne Koritzinsky, Brad Wouters. Cell surface targets in head and neck cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3054.

Somatic Tumor Variant Filtration Strategies to Optimize Tumor-Only Molecular Profiling Using Targeted Next-Generation Sequencing Panels

A common approach in clinical diagnostic laboratories to variant assessment from tumor molecular profiling is sequencing of genomic DNA extracted from both tumor (somatic) and normal (germline) tissue, with subsequent variant comparison to identify true somatic variants with potential impact on patient treatment or prognosis. However, challenges exist in paired tumor-normal testing, including increased cost of dual sample testing and identification of germline cancer predisposing variants. Alternatively, somatic variants can be identified by in silico tumor-only variant filtration precluding the need for matched normal testing. The barrier to tumor-only variant filtration is defining a reliable approach, with high sensitivity and specificity to identify somatic variants. In this study, we used retrospective data sets from paired tumor-normal samples tested on small (48 gene) and large (555 gene) targeted next-generation sequencing panels, to model algorithms for tumor-only variants classification. The optimal algorithm required an ordinal filtering approach using information from variant population databases (1000 Genomes Phase 3, ESP6500, ExAC), clinical mutation databases (ClinVar), and information on recurring clinically relevant somatic variants. Overall the tumor-only variant filtration strategy described in this study can define clinically relevant somatic variants from tumor-only analysis with sensitivity of 97% to 99% and specificity of 87% to 94%, and with significant potential utility for clinical laboratories implementing tumor-only molecular profiling.

Abstract 407: Novel targets in metastatic HNSCC

Head and neck carcinoma (HNSCC) is 6th most common malignancy in the world. Despite advances in diagnosis and treatment, the survival rates remain low due in large part to metastatic disease. The underlying biology associated with metastatic disease and poor outcome in HNSCC remains unclear. Importantly, metastatic cells acquire new properties that permit them to invade surrounding tissues and seed metastasis at distant sites. While these acquired properties contribute to aggressiveness of metastatic cancer and interfere with success of therapies, they can also potentially be exploited to target metastatic cells selectively, sparing toxicity in normal tissues. The idea behind this selective targeting is based on discovering molecular pathways that became essential in metastatic cells, and then exploiting this vulnerability through targeted agents. We used functional genomic technologies to identify new potential therapeutic targets for advanced disease in HNSCC. These targets were identified by conducting whole genome shRNA screens in matched sets of cell lines derived from primary tumors and their respective metastatic sites, with the goal of identifying genes that become essential for cell survival only following metastasis. Since hypoxia is an important attribute of aggressive and therapy resistant subpopulations of HNSCC tumor cells, we also aimed to identify genes that became essential when cells are exposed to hypoxia. To complement the functional screens data, we performed targeted sequencing of the most commonly altered genes in HNSCC as reported by the TCGA profiled gene expression in the HNSCC cell lines cultured under normoxia and hypoxia using Illumina microarrays. These analyses led to the discovery of genes that are differentially essential in metastatic cells as well as in cells exposed to hypoxic conditions. Utilizing CRISPR technology, we assembled a library of guide RNAs targeting the discovered hits and are currently validating the top identified genes using both in vitro and in vivo systems. To validate hits that are essential in metastatic cells in vivo, we engineered selected “matched” pairs of HNSCC cell lines to express CAS9 protein upon induction with doxycycline. The cells are then transduced with the library of guides and injected subcutaneously into mice; tumors from control and doxycycline treated animals are compared. The difference in genes that are essential for growth of tumors seeded by primary tumor derived and metastasis derived HNSCC cell lines is then assessed in a quantitative manner.

Citation Format: Maria Kondratyev, Aleksandra Pesic, Troy Ketela, Azin Sayad, Stephano Marastoni, Jason Mofat, Carl Virtanen, Natalie Stickle, Reider Grenman, Brad Wouters. Novel targets in metastatic HNSCC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 407.

Abstract B09: Efficient generation of patient-matched malignant and normal primary cell cultures from clear cell renal cell carcinoma patients: clinically relevant models for research and personalized medicine

Patients with clear cell renal cell carcinoma (ccRCC) have few therapeutic options, as ccRCC is unresponsive to chemotherapy and is highly resistant to radiation. Recently targeted therapies have extended progression-free survival, but responses are variable and no significant overall survival benefit has been achieved. Commercial ccRCC cell lines are often used as model systems to develop novel therapeutic approaches, but these do not accurately recapitulate primary ccRCC tumors at the genomic and transcriptional levels. Furthermore, ccRCC exhibits significant intertumor genetic heterogeneity, and the limited cell lines available fail to represent this aspect of ccRCC. Our objective was to generate accurate preclinical in vitro models of ccRCC using tumor tissues from ccRCC patients.

ccRCC primary single cell suspensions were cultured in fetal bovine serum (FBS)-containing media or defined serum-free media (DFSM). The apparent efficiency of primary cell culture establishment was high in both culture conditions, but genotyping by single nucleotide polymorphism (SNP) arrays revealed that the majority of cultures in FBS (6 of 8), and all of the cultures in DFSM (8 of 8), contained normal, not cancer cells. To distinguish cancer vs. normal cells in subsequent experiments, we sequenced the von Hippel Lindau (VHL) gene, which is mutated in a large percentage of patients, in a cohort of samples for which cryopreserved viable single cell suspensions were available. Once patients with sequence-detectable mutations were identified, the cells were thawed and cultured as before. Established cultures were then sequenced for the patient-specific VHL mutations. Once again, the majority of cultures in FBS (1 of 7), and all of the cultures in DSFM (7 of 7) contained VHL-wild type cells. The loss of VHL leads to accumulation of hypoxia-inducible factor (HIF) and expression of HIF target genes. Therefore, in an attempt to select for VHL-mutant cancer cells, we used fluorescence activated cell sorting (FACS) to isolate cells expressing Carbonic Anhydrase IX (CA9), a cell surface HIF target. Isolated CA9+ cells were cultured in FBS-containing media, and upon genotyping, we found that VHL-mutant ccRCC cell cultures were established with an efficiency of ~85%. Parallel cultures of bulk single cell suspensions in serum-free conditions again selected for growth of normal (VHL-wild type) cells. The normal cells were verified to be renal proximal tubule epithelial cells based on their expression of renal proximal tubule markers Aquaporin-1 and Alkaline Phosphatase. Transcriptional profiling of ccRCC and matched normal cell cultures identified up- and down-regulated networks in ccRCC and comparison to The Cancer Genome Atlas confirmed the clinical validity of our cell cultures. The ability to establish patient-derived cultures of ccRCC cells and matched normal kidney epithelial cells from almost every patient provides a resource for future development of novel therapies and personalized medicine for ccRCC patients.

Citation Format: Nazleen Lobo, Craig Gedye, Kevin R. Brown, Joshua Paterson, Natalie Stickle, Jason Moffat, Michael A.S. Jewett, Laurie E. Ailles. Efficient generation of patient-matched malignant and normal primary cell cultures from clear cell renal cell carcinoma patients: clinically relevant models for research and personalized medicine. [abstract]. In: Proceedings of the AACR Special Conference: Patient-Derived Cancer Models: Present and Future Applications from Basic Science to the Clinic; Feb 11-14, 2016; New Orleans, LA. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(16_Suppl):Abstract nr B09.

The SH2B1 adaptor protein associates with a proximal region of the erythropoietin receptor

Gene targeting experiments have shown that the cytokine erythropoietin (EPO), its cognate erythropoietin receptor (EPO-R), and associated Janus tyrosine kinase, JAK2, are all essential for erythropoiesis. Structural-functional and murine knock-in experiments have suggested that EPO-R Tyr-343 is important in EPO-mediated mitogenesis. Although Stat5 binds to EPO-R phosphotyrosine 343, the initial Stat5-deficient mice did not have profound erythroid abnormalities suggesting that additional Src homology 2 (SH2) domain-containing effectors may bind to EPO-R Tyr-343 and couple to downstream signaling pathways. We have utilized cloning of ligand target (COLT) screening to demonstrate that EPO-R Tyr(P)-343 and Tyr(P)-401 bind to the SH2 domain-containing adaptor protein SH2B1β. Immunoprecipitation and in vitro mixing experiments reveal that EPO-R binds to SH2B1 in an SH2 domain-dependent manner and that the sequence that confers SH2B1 binding to the EPO-R is pYXXL. Previous studies have shown that SH2B1 binds directly to JAK2, but we show that in hematopoietic cells, SH2B1β preferentially associates with the EPO-R. SH2B1 is capable of constitutive association with EPO-R, which is necessary for its optimal SH2-dependent recruitment to EPO-R-Tyr(P)-343/Tyr(P)-401. We also demonstrate that SH2B1 is responsive to EPO stimulation and becomes phosphorylated, most likely on serines/threonines, in an EPO dose- and time-dependent manner. In the absence of SH2B1, we observe enhanced activation of signaling pathways downstream of the EPO-R, indicating that SH2B1 is a negative regulator of EPO signaling.