Comprehensive assessment of anaplastic lymphoma kinase in localized and metastatic prostate cancer reveals targetable alterations.

Anaplastic lymphoma kinase (ALK) is a tyrosine kinase with genomic and expression changes in many solid tumors. ALK inhibition is first line therapy for lung cancers with ALK alterations, and an effective therapy in other tumor types, but has not been well-studied in prostate cancer. Here, we aim to delineate the role of ALK genomic and expression changes in primary and metastatic prostate cancer. We determined ALK expression by immunohistochemistry and RNA-Seq, and genomic alterations by NGS. We assessed functional consequences of ALK overexpression and pharmacological ALK inhibition by cell proliferation and cell viability assays. Among 372 primary prostate cancer cases we identified one case with uniformly high ALK protein expression. Genomic analysis revealed a SLC45A3-ALK fusion which promoted oncogenesis in in vitro assays. We observed ALK protein expression in 5/52 (9%) of metastatic prostate cancer cases, of which 4 of 5 had neuroendocrine features. ALK-expressing neuroendocrine prostate cancer had a distinct transcriptional program, and earlier disease progression. An ALK-expressing neuroendocrine prostate cancer model was sensitive to pharmacological ALK inhibition. In summary, we found that ALK overexpression is rare in primary prostate cancer, but more frequent in metastatic prostate cancers with neuroendocrine differentiation. Further, ALK fusions similar to lung cancer are an occasional driver in prostate cancer. Our data suggest that ALK-directed therapies could be an option in selected patients with advanced prostate cancer.

Racial Difference in Prostate Cancer Cell Telomere Lengths in Men with Higher Grade Prostate Cancer: A Clue to the Racial Disparity in Prostate Cancer Outcomes.

BACKGROUND: Black men have worse prostate cancer outcomes following treatment than White men even when accounting for prognostic factors. However, biological explanations for this racial disparity have not been fully identified. We previously showed that more variable telomere lengths among cancer cells and shorter telomere lengths in cancer-associated stromal (CAS) cells individually and together ("telomere biomarker") are associated with prostate cancer-related death in surgically treated men independent of currently used prognostic indicators. Here, we hypothesize that Black-White differences in the telomere biomarker and/or in its components may help explain the racial disparity in prostate cancer outcomes. METHODS: Black [higher grade (Gleason ≥4+3) = 34 and lower grade = 93] and White (higher grade = 34 and lower grade = 89) surgically treated men were frequency matched on age, pathologic stage, and grade. We measured telomere lengths in cancer and CAS cells using a robust telomere-specific FISH assay. Tissue microarray and grade-specific distributional cutoff points without regard to race were evaluated. RESULTS: Among men with higher grade disease, the proportion of Black men (47.1%) with more variable cancer cell telomere lengths was 2.3-times higher (P = 0.02) than that in White men (20.6%). In contrast, among men with lower grade disease, cancer cell telomere length variability did not differ by race. The proportion of men with shorter CAS cell telomeres did not differ by race for either higher or lower grade disease. CONCLUSIONS: A greater proportion of Black men with higher grade disease have an adverse prostate cancer cell telomere phenotype than White men with higher grade disease. IMPACT: Our findings suggest a possible explanation for the racial disparity in prostate cancer outcomes.

PTEN status assessment in the Johns Hopkins active surveillance cohort.

BACKGROUND: Up to half of men with Gleason score 6 (GS6) prostate cancers initially managed with active surveillance (AS) will eventually require definitive therapy, usually due to tumor grade reclassification during follow-up. We examined the association between PTEN status on biopsy and subsequent clinicopathologic outcomes in men with GS6 cancers who enrolled in AS. METHODS: We performed a case-control study of men enrolled in the Johns Hopkins AS cohort with diagnostic biopsy tissue available for immunohistochemical (IHC) staining. IHC was performed for PTEN using genetically validated protocols for all patients. Cases included men who underwent grade reclassification to GS ≥ 3 + 4 = 7 on biopsy within 2 years of follow-up (i.e., early reclassification) or reclassification to GS ≥ 4 + 3 = 7 on biopsy or radical prostatectomy during follow-up (i.e., extreme reclassification). Control patients were diagnosed with GS6 cancer and monitored on AS for at least 8 years without undergoing biopsy reclassification. RESULTS: Among 67 cases with adequate tissue, 31 men underwent early reclassification and 36 men underwent extreme reclassification. Cases were compared to 65 control patients with adequate tissue for assessment. On initial prostate biopsy, cases were older (median age 67 vs. 65, p = 0.024) and were less likely to meet very-low-risk criteria (64 vs 79%, p = 0.042) as compared to controls. Although not statistically significant, PTEN loss was observed in only 1 (1.5%) of 65 controls as compared to 6 (9%) of 67 cases (p = 0.062). CONCLUSIONS: PTEN loss was rare among men with GS6 prostate cancer enrolled in AS at Johns Hopkins. Despite this, PTEN loss was more frequent among men who underwent early or extreme reclassification to higher-grade cancer as compared to controls. Additional studies in larger low-risk cohorts may better elucidate a potential role for PTEN in selecting patients for AS.

Telomere length assessment in human archival tissues: combined telomere fluorescence in situ hybridization and immunostaining.

A method was developed to assess human telomere lengths at the individual cell level in tissue sections from standard formalin-fixed paraffin-embedded tissues. We coupled this method with immunofluorescence to allow the simultaneous identification of specific cell types. Validation of this in situ quantification method showed excellent agreement with the commonly used telomere repeat fragment-Southern blot method. The assay requires very few cells ( approximately 10 to 15). Thus, small tissue samples, including clinical biopsies, can be easily accommodated. In addition, the cells under study need not be actively cycling and there is no requirement for tissue disaggregation or cell culture. This method provides a more accurate assessment of telomere lengths than Southern blotting because confounding contributions from undesired cell types within tissue samples are avoided. Using this technique, we were able to perform the first comparison of relative telomere lengths in matched tumor versus normal epithelial cells within archival human prostate tissues.