Targeting histone deacetylation, cell cycle regulators and heat shock proteins as novel therapeutic strategies for penile cancers

Penile carcinoma (PeCa) is a rare malignancy occurring in men. Treatment typically involves penectomy, radiation, or cisplatin-based chemotherapy. A paclitaxel, ifosfamide, and cisplatin-based regimen achieves response rates around 65%. However, non-responders face a 5-year survival rate of only 8%, and due to its rarity, it is mediocrely characterized. Thus, an in-depth delineation of PeCa is crucial to identify novel therapeutic targets. Newly established primary human PeCa cell lines and corresponding xenografts tumors were examined using mass spectrometry and phospho-kinase arrays to analyze the (phospho-)proteome and secretome. Proteomic analyses identified heat shock proteins (HSP27/60/70), factors involved in posttranslational modifications (e.g. acetylation), and the VEGF signaling pathway as putative therapeutic targets. Secreted factors were associated with the HIF-1 and Hippo signaling cascades. Compared to standard chemotherapy (e.g. cisplatin, 5-FU, ifosfamide, irinotecan), treatment with romidepsin, quisinostat (HDAC inhibitors (i)), palbociclib (CDK4/6i), or 17-AAG and PU-H71 (HSP90i) reduced cell viability, induced apoptosis, and led to G2 / M cell cycle arrest in most PeCa cells. This research underscores the therapeutic potential of using HDAC, CDK4/6, and HSP90 inhibitors for PeCa management and reveals additional promising targets and biomarkers for future strategies.