Oxysterol sulfotransferase in prostate cancer inhibition: Cell-intrinsic and -extrinsic roles

Oxysterol sulfotransferase (SULT2B) mediates enzymatic sulfation of oxysterols. SULT2B can modulate lipid metabolism by interfering with oxysterol-induced activation of the LXR nuclear receptor, since sulfated oxysterols are LXR inert. Poor survival is linked to reduced SULT2B in primary prostate cancer, and the enzyme is undetectable in clinical metastases of castration resistant prostate cancer (CRPC). SULT2B-null CRPC xenografts show escalated growth while SULT2B-high tumors are growth suppressed, show reduced tumor-emitted bioluminescence and sustain apoptosis. SULT2B silenced cells are more aggressive - evident from EMT-like induction; activated ERK survival signal; and enhanced invasion. To gain mechanistic insight, we probed PC3 CRPC cells for cell-intrinsic and -extrinsic changes due to ectopic SULT2B expression. Results: Single-cell RNA sequences of SULT2B-high PC3 (SA) & control PC3 (VA) cells revealed transition of neuroendocrine-like PC3 from mesenchymal to epithelial traits afforded by SULT2B. UMAP showed a cluster of SA cells (cluster 7) spatially well-resolved from all other clusters. Bioinformatic probing of cluster 7 cells showed them enriched in epithelial markers and deficient in mesenchymal markers. Down genes in cluster 7 include FOXA2, SOX4, MMP16, Fibronectin 1 - all drivers of lethal CRPC. Notably, CD59 - a sialic acid containing cell surface glycoprotein - is a down gene in cluster 7 and in all SA clusters combined. CD59 is a ligand for Siglec-9 - a lectin that binds sialic acid and resides on macrophages (MΦ) & other myeloids. CD59 binding to Siglec-9 may aid immune evasion since blocking Siglec-9 interaction with sialylated glycoproteins prevented immune cells infiltration to prostate tumor and inhibited PC xenograft (PMID 39436703). Inflammatory genes - such as for NFκB1 & CXCL1, CXCL8 chemokines - are induced in cluster 7 cells and in all SA cell clusters together. RT-qPCR confirmed the changes. AKR1C3 - a key androgen biosynthesis driving enzyme - was elevated in SULT2B-silenced C4-2B CRPC cells in vitro . Multiplex immunofluorescence showed colocalization of CD86 + M1MΦ (pro-inflammatory, immune-boosting) with SULT2B+ cells of SA xenograft, and CD163 + /CD206 + M2MΦ (anti-inflammatory, immune-suppressive) infiltration to AKR1C3 + tumor cells of VA xenograft. AKR1C3 is expressed copiously in VA xenograft, colocalizing with M2MΦ, while it is markedly reduced in M1MΦ-enriched SA xenograft. Reciprocal AKR1C3 and SULT2B expression is consistent with our finding that AKR1C3 is upregulated by oxysterol-LXR signaling. Conclusion: Results highlight dual impacts of SULT2B on CRPC - regulating cancer cell metabolism and also shaping cancer-immune cells interplay by altering MΦ dynamics at tumor microenvironment. In depth molecular insights into cell-intrinsic and -extrinsic roles of SULT2B may uncover new avenue(s) for limiting lethal progression of prostate cancer