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Prostate cancer is a frequent malignancy in older men and has a very high 5‐year survival rate if diagnosed early. The prognosis is much less promising if the tumor has already spread outside the prostate gland. Targeted treatments mainly aim at blocking androgen receptor (AR) signaling and initially show good efficacy. However, tumor progression due to AR‐dependent and AR‐independent mechanisms is often observed after some time, and novel treatment strategies are urgently needed. Dysregulation of the PI3K/AKT/mTOR pathway in advanced prostate cancer and its implication in treatment resistance has been reported. We compared the impact of PI3K/AKT/mTOR pathway inhibitors with different selectivity profiles on in vitro cell proliferation and on caspase 3/7 activation as a marker for apoptosis induction, and observed the strongest effects in the androgen‐sensitive prostate cancer cell lines VCaP and LNCaP. Combination treatment with the AR inhibitor darolutamide led to enhanced apoptosis in these cell lines, the effects being most pronounced upon cotreatment with the pan‐PI3K inhibitor copanlisib. A subsequent transcriptomic analysis performed in VCaP cells revealed that combining darolutamide with copanlisib impacted gene expression much more than individual treatment. A comprehensive reversal of the androgen response and the mTORC1 transcriptional programs as well as a marked induction of DNA damage was observed. Next, an in vivo efficacy study was performed using the androgen‐sensitive patient‐derived prostate cancer (PDX) model LuCaP 35 and a superior efficacy was observed after the combined treatment with copanlisib and darolutamide. Importantly, immunohistochemistry analysis of these treated tumors showed increased apoptosis, as revealed by elevated levels of cleaved caspase 3 and Bcl‐2‐binding component 3 (BBC3). In conclusion, these data demonstrate that concurrent blockade of the PI3K/AKT/mTOR and AR pathways has superior antitumor efficacy and induces apoptosis in androgen‐sensitive prostate cancer cell lines and PDX models.

Abstract The market approval of Tazemetostat (TAZVERIK) for the treatment of follicular lymphoma and epithelioid sarcoma has established “enhancer of zeste homolog 2” (EZH2) as therapeutic target in oncology. Despite their structural similarities and common mode of inhibition, Tazemetostat and other EZH2 inhibitors display differentiated pharmacological profiles based on their target residence time. Here we established high throughput screening methods based on time-resolved fluorescence energy transfer, scintillation proximity and high content analysis microscopy to quantify the biochemical and cellular binding of a chemically diverse collection of EZH2 inhibitors. These assays allowed to further characterize the interplay between EZH2 allosteric modulation by methylated histone tails (H3K27me3) and inhibitor binding, and to evaluate the impact of EZH2’s clinically relevant mutant Y641N on drug target residence times. While all compounds in this study exhibited slower off-rates, those with clinical candidate status display significantly slower target residence times in wild type EZH2 and disease-related mutants. These inhibitors interact in a more entropy-driven fashion and show the most persistent effects in cellular washout and antiproliferative efficacy experiments. Our work provides mechanistic insights for the largest cohort of EZH2 inhibitors reported to date, demonstrating that—among several other binding parameters—target residence time is the best predictor of cellular efficacy.

Lungs have long been considered sterile, but recent research has shown that a large number of microbiological organisms exist in the lungs of healthy subjects (including bacteria, fungi, and viruses), collectively known as the microbiome. It undergoes changes in patients with respiratory pathology. Studies in idiopathic pulmonary fibrosis show that a large number of bacteria or the abundant presence of potentially pathogenic bacteria can cause disease progression and exacerbation, and can implicitly increase mortality. There seems to be a quantitative balance, a well-established proportion between the components of this microbiome, which is disturbed during a disease and can reach a "state of pulmonary dysbiosis". Evidence suggests that the microbiome may be used as a prognostic biomarker and may also explain the pathogenesis of interstitial fibrosis.