NSD2 targeting reverses plasticity and drug resistance in prostate cancer

Treatment with highly potent androgen receptor signaling inhibitors (ARSIs), such as enzalutamide and abiraterone promotes lineage plasticity in metastatic castration-resistant prostate cancer (mCRPC), which results in intra-tumor heterogeneity and emergence of mCRPC subtypes. The histological transformation from adenocarcinoma to aggressive neuroendocrine prostate cancer (CRPC-NE) has been associated with a loss of dependency on lineage-survival signals, leading to targeted drug resistance. Epigenomic reprogramming might be a fundamental driver of lineage plasticity. To determine CRPC-NE vulnerabilities, we have performed image-based screening using a small library of antibodies targeting different histone marks on CRPC-NE organoids derived from genetically engineered mice. We find that the histone mark H3K36me2 and the histone methyltransferase NSD2 (also known as MMSET/WHSC1) play important roles in maintaining the state of CRPC-NE. Knockout of NSD2 or ablation of H3K36me2 using H3.3K36M oncohistone reverted CRPC-NE to CRPC-AR-like phenotype. Simultaneous profiling of the transcriptome and epigenome from single cells collected from control (sgCtrl) and NSD2 knockout (sgNSD2) organoids, or from empty vector (EV) and H3.3K36M transduced organoids confirms the lineage reversal of treatment-resistant cells and maps the re-establishment of canonical AR signaling dependency. Moreover, H3K36me2 or NSD2 depleted mouse and human CRPC-NE organoids responded to enzalutamide treatment in vitro and in vivo, suggesting a restoration of ARSI sensitivity. Most importantly, a small molecule inhibitor of NSD2, which is similar to KTX-1001 (NCT05651932), in combination with enzalutamide leads to growth suppression or apoptosis of mouse and human CRPC-NE organoids, organoids of other CRPC subtypes and xenografts in vitro and in vivo. In conclusion, inhibition of NSD2 reverses lineage plasticity and reverts the state of treatment-resistant cells back into an ARSI-sensitive state. Thus, we suggest that the combination of NSD2 inhibition with AR inhibition may represent a novel therapeutic approach for patients with CRPC-NE and other CRPC subtypes.