Abstract 1343: Mesenchymal cell populations associated with different stages of prostate cancer progression in mice and human

Mesenchymal cells in the prostate cancer (PCa) tumor microenvironment (TME) contribute to the biological and clinical history of PCa. Indeed, mesenchymal cells heavily interact with cancer cells, immune cells, and the other cellular and non-cellular components of the TME to favor or hinder carcinogenesis and tumor progression. Using a comprehensive array of genetically engineered mouse models (GEMMs) of prostate cancer, 8 mesenchymal populations with different transcriptional programs are preferentially enriched in specific GEMMs at different stages of PCa. Here, we determine the transferability of this mesenchymal cluster designation from mice PCa models to human PCa cases. To this end, we compared: a) Tmprss2-ERG (T-ERG) mouse and ERG+ human cases; b) Pb4-Cre+/-;Ptenf/f;LSL-MYCN+/+;Rb1f/f (PRN) mouse and PCa bone metastasis. We generated scRNA-seq data for > 8000 mesenchymal cells from ERG+ (n=6) and ERG- (n=3) PCa patients, and we retrieved data for bone metastasis mesenchymal cells (osteoblasts, osteoclasts, endothelial cells, pericytes; 1,872 total cells) from GSE143791. To transfer the stromal mouse clusters’ labels to human data, human gene symbols were converted to their mouse counterparts, then both datasets were restricted to overlapping genes. For the human PCa cases, label transfer was performed through ‘ingest’ using the scRNA-seq data from the mouse T-ERG model as reference for the human ERG+ cases and data from the remaining GEMMs as reference for the human ERG- cases. For bone metastases cases, mouse stromal data from all GEMMs were used to project the 8 stromal clusters to the mesenchymal cells in the bone metastases microenvironment. Not surprisingly, ERG+ human samples were enriched (> 60% of total stromal cells) in mouse stroma clusters predominantly present in T-ERG mouse model, characterized by the expression of Wnt regulators and AR. Common populations to all murine models, representing myofibroblasts and immunomodulatory fibroblasts (expressing Gpx3, C3, C7, Cfh), were also commonly present in patients, irrespectively to the ERG status. In the PCa bone metastases, mesenchymal clusters enriched in the PRN model were strongly represented in human bone metastases, comprising > 60% of total stromal cells. These cells were characterized by high expression of POSTN and MKI67, as well as bone-specific genes like BGN. Altogether, these findings suggest that our mesenchymal cluster designation developed using GEMMs can be meaningfully applied to human PCa, and that the different transcriptional programs we identified in distinct mesenchymal population are conserved across species. This lays the foundation for the utilization of defined genetically-engineered models in defining the interactions and cross-talks between different mesenchymal populations in relation to cancer and immune cells and other components of the TME in human prostate cancer.

Citation Format: Mohamed Omar, Hubert Pakula, Filippo Pederzoli, Giuseppe N. Fanelli, Tania Panellinni, Ryan Carelli, Silvia Rodrigues, Caroline Fidalgo-Ribeiro, Pier V. Nuzzo, Lucie V. Emmenis, Mohammad Mohammad, Madhavi Jere, Caitlin Unkenholz, David Rickman, Christopher Barbieri, Brian Robinson, Luigi Marchionni, Massimo Loda. Mesenchymal cell populations associated with different stages of prostate cancer progression in mice and human [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 1343.

Distinct mesenchymal cell states mediate prostate cancer progression

Alterations in tumor stroma influence prostate cancer progression and metastatic potential. However, the molecular underpinnings of this stromal-epithelial crosstalk are largely unknown. Here, we compare mesenchymal cells from four genetically engineered mouse models (GEMMs) of prostate cancer representing different stages of the disease to their wild-type (WT) counterparts by single-cell RNA sequencing (scRNA-seq) and, ultimately, to human tumors with comparable genotypes. We identified 8 transcriptionally and functionally distinct stromal populations responsible for common and GEMM-specific transcriptional programs. We show that stromal responses are conserved in mouse models and human prostate cancers with the same genomic alterations. We noted striking similarities between the transcriptional profiles of the stroma of murine models of advanced disease and those of of human prostate cancer bone metastases. These profiles were then used to build a robust gene signature that can predict metastatic progression in prostate cancer patients with localized disease and is also associated with progression-free survival independent of Gleason score. Taken together, this offers new evidence that stromal microenvironment mediates prostate cancer progression, further identifying tissue-based biomarkers and potential therapeutic targets of aggressive and metastatic disease.

Distinct mesenchymal cell states mediate prostate cancer progression

Alterations in tumor stroma influence prostate cancer progression and metastatic potential. However, the molecular underpinnings of this stromal-epithelial crosstalk are largely unknown. Here, we compare mesenchymal cells from four genetically engineered mouse models (GEMMs) of prostate cancer representing different stages of the disease to their wild-type (WT) counterparts by single-cell RNA sequencing (scRNA-seq) and, ultimately, to human tumors with comparable genotypes. We identified 8 transcriptionally and functionally distinct stromal populations responsible for common and GEMM-specific transcriptional programs. We show that stromal responses are conserved in mouse models and human prostate cancers with the same genomic alterations. We noted striking similarities between the transcriptional profiles of the stroma of murine models of advanced disease and those of of human prostate cancer bone metastases. These profiles were then used to build a robust gene signature that can predict metastatic progression in prostate cancer patients with localized disease and is also associated with progression-free survival independent of Gleason score. Taken together, this offers new evidence that stromal microenvironment mediates prostate cancer progression, further identifying tissue-based biomarkers and potential therapeutic targets of aggressive and metastatic disease.

Germline variants associated with toxicity to immune checkpoint blockade

Immune checkpoint inhibitors (ICIs) have yielded remarkable responses but often lead to immune-related adverse events (irAEs). Although germline causes for irAEs have been hypothesized, no individual variant associated with developing irAEs has been identified. We carried out a genome-wide association study of 1,751 patients on ICIs across 12 cancer types. We investigated two irAE phenotypes: (1) high-grade (3-5) and (2) all-grade events. We identified 3 genome-wide significant associations (P < 5 × 10-8) in the discovery cohort associated with all-grade irAEs: rs16906115 near IL7 (combined P = 3.6 × 10-11; hazard ratio (HR) = 2.1); rs75824728 near IL22RA1 (combined P = 3.5 × 10-8; HR = 1.8); and rs113861051 on 4p15 (combined P = 1.2 × 10-8, HR = 2.0); rs16906115 was replicated in 3 independent studies. The association near IL7 colocalized with the gain of a new cryptic exon for IL7, a critical regulator of lymphocyte homeostasis. Patients carrying the IL7 germline variant exhibited significantly increased lymphocyte stability after ICI initiation, which was itself predictive of downstream irAEs and improved survival.

Oncology clinical trial disruption during the COVID-19 pandemic: a COVID-19 and cancer outcomes study

Background

COVID-19 disproportionately impacted patients with cancer as a result of direct infection, and delays in diagnosis and therapy. Oncological clinical trials are resource-intensive endeavors that could be particularly susceptible to disruption by the pandemic, but few studies have evaluated the impact of the pandemic on clinical trial conduct.

Patients and methods

This prospective, multicenter study assesses the impact of the pandemic on therapeutic clinical trials at two large academic centers in the Northeastern United States between December 2019 and June 2021. The primary objective was to assess the enrollment on, accrual to, and activation of oncology therapeutic clinical trials during the pandemic using an institution-wide cohort of (i) new patient accruals to oncological trials, (ii) a manually curated cohort of patients with cancer, and (ii) a dataset of new trial activations.

Results

The institution-wide cohort included 4756 new patients enrolled to clinical trials from December 2019 to June 2021. A major decrease in the numbers of new patient accruals (−46%) was seen early in the pandemic, followed by a progressive recovery and return to higher-than-normal levels (+2.6%). A similar pattern (from −23.6% to +30.4%) was observed among 467 newly activated trials from June 2019 to June 2021. A more pronounced decline in new accruals was seen among academically sponsored trials (versus industry sponsored trials) (P < 0.05). In the manually curated cohort, which included 2361 patients with cancer, non-white patients tended to be more likely taken off trial in the early pandemic period (adjusted odds ratio: 2.60; 95% confidence interval 1.00-6.63), and substantial pandemic-related deviations were recorded.

Conclusions

Substantial disruptions in clinical trial activities were observed early during the pandemic, with a gradual recovery during ensuing time periods, both from an enrollment and an activation standpoint. The observed decline was more prominent among academically sponsored trials, and racial disparities were seen among people taken off trial.

Care disruptions among patients with lung cancer: A COVID-19 and cancer outcomes study

Introduction

Patients with lung cancer (LC) are susceptible to severe outcomes from COVID-19. This study evaluated disruption to care of patients with LC during the COVID-19 pandemic.

Methods

The COVID-19 and Cancer Outcomes Study (CCOS) is a prospective cohort study comprised of patients with a current or past history of hematological or solid malignancies with outpatient visits between March 2 and March 6, 2020, at two academic cancer centers in the Northeastern United States (US). Data was collected for the three months prior to the index week (baseline period) and the following three months (pandemic period).

Results

313 of 2365 patients had LC, 1578 had other solid tumors, and 474 had hematological malignancies. Patients with LC were not at increased risk of COVID-19 diagnosis compared to patients with other solid or hematological malignancies. When comparing data from the pandemic period to the baseline period, patients with LC were more likely to have a decrease in in-person visits compared to patients with other solid tumors (aOR 1.94; 95% CI, 1.46–2.58), but without an increase in telehealth visits (aOR 1.13; 95% CI 0.85–1.50). Patients with LC were more likely to experience pandemic-related treatment delays than patients with other solid tumors (aOR 1.80; 95% CI 1.13–2.80) and were more likely to experience imaging/diagnostic procedure delays than patients with other solid tumors (aOR 2.59; 95% CI, 1.46–4.47) and hematological malignancies (aOR 2.01; 95% CI, 1.02–3.93). Among patients on systemic therapy, patients with LC were also at increased risk for decreased in-person visits and increased treatment delays compared to those with other solid tumors.

Discussion

Patients with LC experienced increased cancer care disruption compared to patients with other malignancies during the early phase of the COVID-19 pandemic. Focused efforts to ensure continuity of care for this patient population are warranted.

Abstract S06-02: Disruption to care of patients with thoracic malignancies: A COVID-19 and cancer outcomes study

Introduction: Patients with thoracic malignancies are susceptible to severe outcomes from coronavirus disease 2019 (COVID-19). The aim of this study was to evaluate the disruption to care of patients with thoracic malignancies during the COVID-19 pandemic. Methods: The COVID-19 and Cancer Outcomes Study (CCOS) is a multicenter prospective cohort study comprised of adult patients with a current or past history of hematological malignancy or invasive solid tumor who had an outpatient medical oncology visit on the index week between March 2 and March 6, 2020 at the Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai in New York, NY (MSSM) or the Dana-Farber Cancer Institute in Boston, MA (DFCI). An electronic data capture platform was used to collect patient-, cancer-, and treatment-related variables during the three months prior to the index week (the baseline period) and the following three months (the pandemic period). Two-by-three contingency tables with Fisher’s exact tests were computed. All tests were two-tailed and considered statistically significant for p&lt;0.05. All analyses were done in the R statistical environment (v3.6.1). Results: The overall cohort included 2365 patients, of which 313 had thoracic malignancies, 1578 had other solid tumors, and 474 had hematological malignancies. At a median follow-up of 84 days (95% confidence interval, 82-84), 13 patients with thoracic malignancies (4.1%) had developed COVID-19 (vs. other solid: 63 [4.0%] and hematological: 52 [11.0%]; p&lt;0.001). When comparing data from the pandemic period to the baseline period, patients with thoracic malignancies had a decrease in the number of in-person outpatient visits (thoracic: 209 [66.8%] vs. other solid: 749 [47.5%] vs. hematological: 260 [54.9%]; p&lt;0.001) and an increase in the number of telehealth visits (thoracic: 126 [40.3%] vs. other solid: 465 [29.5%] vs. hematological: 168 [35.4%]; p&lt;0.001). During the pandemic period, 33 (10.5%) patients with thoracic malignancies experienced treatment delays due to the pandemic (vs. other solid: 127 [8.0%] and hematological: 79 [16.7%]; p&lt;0.001), and 26 (8.3%) patients with thoracic malignancies experienced delays in cancer imaging or diagnostic procedures (vs. other solid: 63 [4.0%] and hematological: 26 [5.5%]; p=0.003). Discussion: In this prospective cohort study, patients with thoracic malignancies were not at increased risk of developing COVID-19 compared to patients with other cancers, but experienced significant cancer care disruption during the COVID-19 pandemic with a higher likelihood of decreased in-person visits and increased telehealth visits compared to patients with other malignancies. Focused efforts to ensure continuity of care for this vulnerable patient population are warranted.

Citation Format: Sheena Bhalla, Ziad Bakouny, Andrew L. Schmidt, John A. Steinharter, Douglas A. Tremblay, Mark M. Awad, Alaina J. Kessler, Robert I. Haddad, Michelle Evans, Fiona Busser, Michael Wotman, Catherine R. Curran, Brittney S. Zimmerman, Gabrielle Bouchard, Tomi Jun, Pier V. Nuzzo, Qian Qin, Laure Hirsch, Jonathan Feld, Kaitlin M Kelleher, Danielle Seidman, Hsin-Hui Huang, Chris Labaki, Heather M. Anderson-Keightly, Sarah Abou Alaiwi, Talia D. Rosenbloom, Penina S. Stewart, Matthew D. Galsky, Toni K. Choueiri, Deborah B. Doroshow. Disruption to care of patients with thoracic malignancies: A COVID-19 and cancer outcomes study [abstract]. In: Proceedings of the AACR Virtual Meeting: COVID-19 and Cancer; 2021 Feb 3-5. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(6_Suppl):Abstract nr S06-02.

Prevalence of pathogenic germline cancer risk variants in high-risk urothelial carcinoma

Purpose

To date, there has not been a large, systematic evaluation of the prevalence of germline risk variants in urothelial carcinoma (UC).

Methods

We evaluated the frequency of germline pathogenic and likely pathogenic variants in 1038 patients with high-risk UC who underwent targeted clinical germline testing. Case–control enrichment analysis was performed to screen for pathogenic variant enrichment in 17 DNA repair genes in 1038 UC patients relative to cancer-free individuals.

Results

Among 1038 patients with UC, the cumulative frequency of patients with pathogenic variants was 24%; 18.6% of patients harbored ≥1 actionable germline variant with preventive or therapeutic utility. MSH2 (34/969, 3.5%) and BRCA1/2 (38/867, 4.4%) germline variants had the highest frequency. Germline variants in DNA damage repair genes accounted for 78% of pathogenic germline variants. Compared to the cancer-free cohort, UC patients had significant variant enrichment in MSH2 (odds ratio [OR]: 15.4, 95% confidence interval [CI]: 7.1–32.7, p < 0.0001), MLH1 (OR: 15.9, 95% CI: 4.4–67.7, p < 0.0001), BRCA2 (OR: 5.7, 95% CI: 3.2–9.6, p < 0.0001), and ATM (OR: 3.8, 95% CI: 1.8–8.3, p = 0.02).

Conclusion

In this study, 24% of UC patients harbored pathogenic germline variants and 18.6% had clinically actionable variants. MLH1 and MSH2 were validated as UC risk genes while ATM and BRCA2 were highlighted as potential UC predisposition genes. This work emphasizes the utility of germline testing in selected high-risk UC cohorts.

Differential side effects profile in patients with mCRPC treated with abiraterone or enzalutamide: a meta-analysis of randomized controlled trials

Background

Abiraterone and enzalutamide are currently approved for mCRPC patients. Both drugs have distinct mechanisms of action and may have different toxicity profile. There are limited data comparing the side effects of abiraterone and enzalutamide. We performed a meta-analysis of randomized controlled trials (RCT) to better characterize the risk of adverse events associated with both drugs.

Methods

We performed a literature search on MEDLINE for studies reporting abiraterone and enzalutamide side effects from January 1966 to July 31, 2015. Abstracts presented at ASCO meetings from 2004 to 2015 were selected manually. Phase III RCT were included in analysis. We assessed the risk of adverse events reported in RCT by performing two meta-analyses: abiraterone-prednisone vs. placebo-prednisone (2,283 pts) and enzalutamide vs. placebo (2,914 pts). Summary of incidence, relative-risks (RR), and 95% confidence intervals (CI) were calculated using random-effects or fixed-effects models based on the heterogeneity of included studies.

Results

Overall, enzalutamide was not associated with all-grade (RR 1.06 - 95% CI 0.67-1.65) or grade ≥3 (RR 0.81 - 95% CI 0.28-2.33) cardiovascular events, but was associated with increased risk of all-grade fatigue (RR 1.29 - 95% CI 1.15-1.44). On the other hand, abiraterone was associated with increased risk of all-grade (RR 1.28 - 95% CI 1.06-1.55) and grade ≥3 (RR 1.76 - 95% CI 1.12-2.75) cardiovascular events, but was not associated with all-grade (RR 0.85 - 95% CI 0.58-1.23) or grade ≥3 (RR 1.07 - 95% CI 0.97-1.19) fatigue.

Conclusions

In this meta-analysis, abiraterone was associated with an increased risk of cardiovascular events, while enzalutamide was associated with an increased risk of fatigue.

The prognostic value of stromal and epithelial periostin expression in human breast cancer: correlation with clinical pathological features and mortality outcome

Background

PN is a secreted cell adhesion protein critical for carcinogenesis. In breast cancer, it is overexpressed compared to normal breast, and a few reports suggest that it has a potential role as a prognostic marker.

Methods

Tumour samples obtained at the time of mastectomy from 200 women followed for a median time of 18.7 years (range 0.5–29.5 years) were investigated through IHC with a polyclonal anti-PN antibody using tissue microarrays. Epithelial and stromal PN expression were scored independently according to the percentage of coloured cells; the 60^th percentile of PN epithelial expression, corresponding to 1 %, and the median value of PN stromal expression, corresponding to 90 %, were used as arbitrary cut-offs. The relationships between epithelial and stromal PN expression and clinical-pathological features, tumour phenotype and the risk of mortality following surgery were analysed. Appropriate statistics, including the Fine and Gray competing risk proportional hazard regression model, were used.

Results

The expression of PN in tumour epithelial cells was significantly lower than that which was observed in stromal cells (p < 0.000). No specific association between epithelial or stromal PN expression and any of the clinical-pathological parameters analysed was found as it was observed in respect to mortality when these variables were analysed individually. However, when both variables were considered as a function of the other one, the expression of PN in the stromal cells maintained a statistically significant predictive value with respect to both all causes and cancer-specific mortality only in the presence of high epithelial expression levels. No significant differences in either all causes or BCa-specific mortality rates were shown according to epithelial expression for tumours displaying higher stromal PN expression rates. However, the trends were opposite for the higher stromal values and the patients with high epithelial expression levels denoted the group with the worst prognosis, while higher epithelial values in patients with lower stromal expression levels denoted the group with the best prognosis, suggesting that PN epithelial/stromal interactions play a crucial role in breast carcinogenesis, most likely due to functional cross-talk between the two compartments. On the basis of PN expression in both compartments, we defined 4 subgroups of patients with different mortality rates with the group of patients characterized by positive epithelial and low stromal PN expression cells showing the lowest mortality risk as opposed to the groups of patients identified by a high PN expression in both cell compartments or those identified by a low or absent PN expression in both cell compartments showing the worst mortality rates. The differences were highly statistically significant and were also retained after multiparametric analysis. Competing risk analysis demonstrated that PN expression patterns characterizing each of previous groups are specifically associated with cancer-specific mortality.

Conclusions

Although they require further validation through larger studies, our findings suggest that the patterns of expression of PN in both compartments can allow for the development of IHC “signatures” that maintain a strong independent predictive value of both all causes and, namely, of cancer-specific mortality.