Hailiang Hu

Hormonal therapy targeting androgen receptor (AR) is initially effective to treat prostate cancer (PCa), but it eventually fails. It has been hypothesized that cellular heterogeneity of PCa, consisting of AR+ luminal tumor cells and AR- neuroendocrine (NE) tumor cells, may contribute to therapy failure. Here, we describe the successful purification of NE cells from primary fresh human prostate adenocarcinoma based on the cell surface receptor C-X-C motif chemokine receptor 2 (CXCR2). Functional studies revealed CXCR2 to be a driver of the NE phenotype, including loss of AR expression, lineage plasticity, and resistance to hormonal therapy. CXCR2-driven NE cells were critical for the tumor microenvironment by providing a survival niche for the AR+ luminal cells. We demonstrate that the combination of CXCR2 inhibition and AR targeting is an effective treatment strategy in mouse xenograft models. Such a strategy has the potential to overcome therapy resistance caused by tumor cell heterogeneity.

Following publication of the original article [1], the authors reported that name that appeared in published online version is incorrect. Aifeng Wang should be Aifen Wang. Corrected name is provided in the author group section above.

BACKGROUND: MYCN amplification or N-Myc overexpression is found in approximately 40% NEPC and up to 20% CRPC patients. N-Myc has been demonstrated to drive disease progression and hormonal therapeutic resistance of NEPC/CRPC. Here, we aim to identify the molecular mechanisms underlying the N-Myc-driven therapeutic resistance and provide new therapeutic targets for those N-Myc overexpressed NEPC/CRPC. METHODS: N-Myc overexpressing stable cell lines for LNCaP and C4-2 were generated by lentivirus infection. ADT-induced senescence was measured by SA-β-gal staining in LNCaP cells in vitro and in LNCaP xenograft tumors in vivo. Migration, cell proliferation and colony formation assays were used to measure the cellular response after overexpressing N-Myc or perturbing the miR-421/ATM pathway. CRISPR-Cas9 was used to knock out ATM in C4-2 cells and MTS cell viability assay was used to evaluate the drug sensitivity of N-Myc overexpressing C4-2 cells in response to Enzalutamide and ATM inhibitor Ku60019 respectively or in combination. RESULTS: N-Myc overexpression suppressed ATM expression through upregulating miR-421 in LNCaP cells. This suppression alleviated the ADT-induced senescence in vitro and in vivo. Surprisingly, N-Myc overexpression upregulated ATM expression in C4-2 cells and this upregulation promoted migration and invasion of prostate cancer cells. Further, the N-Myc-induced ATM upregulation in C4-2 cells rendered the cells resistance to Enzalutamide, and inhibition of ATM by CRISPR-Cas9 knockout or ATM inhibitor Ku60019 re-sensitized them to Enzalutamide. CONCLUSIONS: N-Myc differentially regulating miR-421/ATM pathway contributes to ADT resistance and Enzalutamide resistance development respectively. Combination treatment with ATM inhibitor re-sensitizes N-Myc overexpressed CRPC cells to Enzalutamide. Our findings would offer a potential combination therapeutic strategy using ATM kinase inhibitor and Enzalutamide for the treatment of a subset of mCRPC with N-Myc overexpression that accounts for up to 20% CRPC patients.

ATM is a well-known master regulator of double strand break (DSB) DNA repair and the defective DNA repair has been therapeutically exploited to develop PARP inhibitors based on the synthetic lethality strategy. ATM mutation is found with increased prevalence in advanced metastatic castration-resistant prostate cancer (mCRPC). However, the molecular mechanisms underlying ATM mutation-driving disease progression are still largely unknown. Here, we report that ATM mutation contributes to the CRPC progression through a metabolic rather than DNA repair mechanism. We showed that ATM deficiency generated by CRISPR/Cas9 editing promoted CRPC cell proliferation and xenograft tumor growth. ATM deficiency altered cellular metabolism and enhanced Warburg effect in CRPC cells. We demonstrated that ATM deficiency shunted the glucose flux to aerobic glycolysis by upregulating LDHA expression, which generated more lactate and produced less mitochondrial ROS to promote CRPC cell growth. Inhibition of LDHA by siRNA or inhibitor FX11 generated less lactate and accumulated more ROS in ATM-deficient CRPC cells and therefore potentiated the cell death of ATM-deficient CRPC cells. These findings suggest a new therapeutic strategy for ATM-mutant CRPC patients by targeting LDHA-mediated glycolysis metabolism, which might be effective for the PARP inhibitor resistant mCRPC tumors.

Since androgen receptor (AR) signaling is critically required for the development of prostate cancer (PCa), targeting AR axis has been the standard treatment of choice for advanced and metastatic PCa. Unfortunately, although the tumor initially responds to the therapy, treatment resistance eventually develops and the disease will progress. It is therefore imperative to identify the mechanisms of therapeutic resistance and novel molecular targets that are independent of AR signaling. Recent advances in pathology, molecular biology, genetics and genomics research have revealed novel AR-independent pathways that contribute to PCa carcinogenesis and progression. They include neuroendocrine differentiation, cell metabolism, DNA damage repair pathways and immune-mediated mechanisms. The development of novel agents targeting the non-AR mechanisms holds great promise to treat PCa that does not respond to AR-targeted therapies.