Gao, Allen C

Abstract Intraductal carcinoma of the prostate (IDC-P) is a lethal prostate cancer subtype that generally coexists with invasive high-grade prostate acinar adenocarcinoma (PAC) but exhibits distinct biological features compared with concomitant adenocarcinoma. In this study, we performed whole-exome, RNA, and DNA-methylation sequencing of IDC-P, concurrent invasive high-grade PAC lesions, and adjacent normal prostate tissues isolated from 22 radical prostatectomy specimens. Three evolutionary patterns of concurrent IDC-P and PAC were identified: early divergent, late divergent, and clonally distant. In contrast to those with a late divergent evolutionary pattern, tumors with clonally distant and early divergent evolutionary patterns showed higher genomic, epigenomic, transcriptional, and pathologic heterogeneity between IDC-P and PAC. Compared with coexisting PAC, IDC-P displayed increased expression of adverse prognosis–associated genes. Survival analysis based on an independent cohort of 505 patients with metastatic prostate cancer revealed that IDC-P carriers with lower risk International Society of Urological Pathology (ISUP) grade 1–4 adenocarcinoma displayed a castration-resistant free survival as poor as those with the highest risk ISUP grade 5 tumors that lacked concurrent IDC-P. Furthermore, IDC-P exhibited robust cell-cycle progression and androgen receptor activities, characterized by an enrichment of cellular proliferation–associated master regulators and genes involved in intratumoral androgen biosynthesis. Overall, this study provides a molecular groundwork for the aggressive behavior of IDC-P and could help identify potential strategies to improve treatment of IDC-P. Significance: The genomic, transcriptomic, and epigenomic characterization of concurrent intraductal carcinoma and adenocarcinoma of the prostate deepens the biological understanding of this lethal disease and provides a genetic basis for developing targeted therapies.

Objectives To investigate the genetic alterations of patients with prostate cancer (PCa) with and without intraductal carcinoma of the prostate (IDC‐P). Patients and Methods We performed targeted sequencing of plasma cell‐free DNA on 161 patients with prostate adenocarcinoma (PAC) with IDC‐P and 84 without IDC‐P. Genomic alterations were compared between these two groups. The association between genetic alterations and patients’ survival outcomes was also explored. Results We identified that 29.8% (48/161) and 21.4% (18/84) of patients with and without IDC‐P harboured genomic alterations in DNA repair pathways, respectively ( P = 0.210). Pathogenic germline DNA repair alterations were frequently detected in IDC‐P carriers compared to IDC‐P non‐carriers (11.8% [19/161] vs 2.4% [two of 84], P = 0.024). Germline BReast CAncer type 2 susceptibility protein ( BRCA2 ) and somatic cyclin‐dependent kinase 12 ( CDK12 ) defects were specifically identified in IDC‐P carriers relative to PAC ( BRCA2 : 8.7% [14/161] vs 0% and CDK12 : 6.8% [11/161] vs 1.2% [one of 84]). Patients with IDC‐P had a distinct androgen receptor (AR) pathway alteration, characterised by an enrichment of nuclear receptor corepressor 2 ( NCOR2 ) mutations compared with patients with pure PAC (21.1% [34/161] vs 6.0% [five of 84], P = 0.004). Increased AR alterations were detected in patients harbouring tumours with an IDC‐P proportion of ≥10% vs those with an IDC‐P proportion of <10% (6.4% [five of 78] vs 18.1% [15/83], P = 0.045). For IDC‐P carriers, tumour protein p53 ( TP53 ) mutation was associated with shorter castration‐resistant‐free survival (median 10.9 vs 28.9 months, P = 0.026), and BRCA2 alteration was related to rapid prostate‐specific antigen progression for those receiving abiraterone treatment (median 9.1 vs 11.9 months, P = 0.036). Conclusion Our findings provide genomic evidence explaining the aggressive phenotype of tumours with IDC‐P, highlighting the potential therapeutic strategies for this patient population.

Abstract The present project was undertaken to determine whether the activation of the EGFR family (EGFR/ErbB2/ErbB3/ErbB4) and its downstream signaling effector ERK1/2 plays a role in enzalutamide resistance and whether treatment with ErbB or ERK inhibitors overcome this resistance. C4-2B (enzalutamide sensitive) and 22Rv1 (partially enzalutamide resistant) cell lines cultured for prolonged periods in enzalutamide, developed resistance to this drug (C4-2B/MDVR and 22Rv1/MDVR, respectively). Whole genome comparison of enza-resistant to parental lines demonstrated that the ErbB signaling network was significantly upregulated in the enza-resistant lines. Comparison of various enza-sensitive and resistant lines demonstrated a strong correlation between phosphorylation at EGFR(Y1068) and enza resistance. Inhibition of EGFR, but not that of ErbB2 or ErbB3 prevented cell viability. The EGFR inhibitors erlotinib and dacomitinib, but not the ErbB2 inhibitor lapatinib, suppressed viability in combination with enzalutamide. We hypothesized that enza-resistant tumors expressing higher levels of EGFR would be more responsive to erlotinib. To test this hypothesis, we compared the effects of erlotinib and enzalutamide, individually or in combination, in organelles from PDX tumors expressing high or low EGFR levels. Significantly, tumors expressing high EGFR, but not those expressing low EGFR, were responsive to the combination. Finally, we investigated the cause for greater efficacy with erlotinib compared to lapatinib in PCa. Comparison of the effects of different ligands revealed that while both lapatinib and erlotinib inhibited EGFR phosphorylation, only erlotinib but not lapatinib was able to inhibit EGF-induced ERK phosphorylation. This indicated an important role for ERK in the mediation of EGFR ligand induced enzalutamide resistance. Continuous culture of enza-sensitive C4 cells in enzalutamide resulted in the development of ERK phosphorylation in these PTEN-null cells that normally do not express phosphorylated ERK, and the newly ERK phosphorylated cells also were more susceptible to erlotinib as well. In support of a role for ERK in mediating the effects of EGFR activation in enza-resistant cells, inhibition of EGFR but not ErbB2 or ErbB3 inhibited ERK phosphorylation, and the ERK inhibitor ulitertinib inhibited viability of enza-resistant lines. We conclude that enzalutamide treatment causes an increase in EGFR ligands that result in the phosphorylation of EGFR at Y1068, which further resulted in phosphorylation of ERK. EGFR inhibitors that prevent ERK phosphorylation were effective in suppressing viability of enza-resistant CRPC cells, whereas ErbB2 inhibitors that did not affect ERK phosphorylation were unable to affect cell viability. These results demonstrate why certain ErbB inhibitors failed to affect enza-resistant CRPC tumors but provide encouragement for others. Citation Format: Thomas M. Steele, Maitreyee K. Jathal, Salma Siddiqui, Sisi Qin, Clifford G. Tepper, Ralph W. deVere White, Manish Kohli, Liewei Wang, Allen C. Gao, Paramita M. Ghosh. Overcoming EGFR and ERK-mediated resistance to enzalutamide in castration-resistant prostate 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 4842.