Smoothened loss is a characteristic of neuroendocrine prostate cancer
Lili Wang1, Haiying Li1, Zhang Li1
1Department of Clinical Laboratory, Shandong Provincial Hospital, Cheeloo College of Medicine, Shandong University, Jinan, China.
Purpose:
Hedgehog (Hh) signaling promotes castration-resistant prostate cancer by supporting androgen-independent prostate cancer cell development and growth; however, its role in neuroendocrine prostate cancer (NEPC) has not yet been explored. In this study, we assessed the expression of key genes involved in Hh signaling in prostate cancer and investigated the potential role of smoothened (SMO) in the pathogenesis of NEPC.
Methods:
Six public datasets, each containing cases of prostate adenocarcinoma (AdPC) and NEPC, were analyzed to compare the differential messenger RNA (mRNA) expression of six classic Hh signaling genes. The SMO, synaptophysin, chromogranin A (CHGA) and androgen receptor (AR) proteins were evaluated in human tissues from 5 cases of NEPC, 2 cases of AdPC mixed with NEPC, 2 cases of AdPC with neuroendocrine differentiation and 22 cases of high-grade AdPC as determined by an immunohistochemistry assay. Gene set enrichment analysis (GSEA) was performed to identify relevant genetic signatures associated with SMO expression based on the public datasets. Stable SMO-knockdown LNCaP and C4-2B cells were established with a lentiviral system, and the expression of SMO, Gli1, AR, prostate-specific antigen (PSA), and REST was assessed by real-time polymerase chain reaction and western blot. Secreted PSA in the conditioned medium was assessed by ELISA. Gli1 was ectopically expressed performed by the transfection of Gli1 complementary DNA into SMO-knockdown LNCaP cells, and western blot was used to assess of AR and PSA expression.
Results:
The mRNA level of SMO was dramatically downregulated in NEPC samples compared with AdPC samples in all 6 public datasets. SMO protein loss was observed in 100% of NEPC samples but in only 9% (2 of 22) of high-grade AdPC samples. GSEA results showed that SMO loss was closely correlated with AR signaling activity. Stable SMO knockdown significantly attenuated AR signaling activity and suppressed AR expression, while Gli1 overexpression partially reversed the inhibitory effects of SMO knockdown on AR signaling activity and AR expression in LNCaP and C4-2B cells.
Conclusion:
These results demonstrate that SMO loss is a characteristic of NEPC and that detecting SMO by IHC could aid pathologists in NEPC diagnosis. SMO loss may promote NEPC pathogenesis by modulating AR signaling.
Insights
SMO loss is a hallmark of neuroendocrine prostate cancer (NEPC), potentially aiding diagnosis. This loss may drive NEPC by affecting androgen receptor (AR) signaling pathways.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Research
Background:
- Hedgehog (Hh) signaling is implicated in castration-resistant prostate cancer.
- The role of Hh signaling in neuroendocrine prostate cancer (NEPC) remains unexplored.
Purpose of the Study:
- To investigate the expression of Hh signaling genes in NEPC.
- To determine the role of smoothened (SMO) in NEPC pathogenesis.
Main Methods:
- Analysis of six public prostate cancer datasets for differential mRNA expression of Hh signaling genes.
- Immunohistochemistry (IHC) to evaluate SMO, synaptophysin, chromogranin A (CHGA), and androgen receptor (AR) protein expression in human prostate cancer tissues.
- Gene set enrichment analysis (GSEA) to correlate SMO expression with genetic signatures.
- In vitro studies using SMO-knockdown LNCaP and C4-2B cells to assess AR signaling and expression.
Main Results:
- SMO mRNA was significantly downregulated in NEPC compared to adenocarcinoma (AdPC).
- SMO protein loss was observed in all NEPC samples but rare in high-grade AdPC.
- SMO loss correlated with reduced AR signaling activity and AR expression.
- Gli1 overexpression partially rescued the effects of SMO knockdown on AR signaling.
Conclusions:
- SMO loss is a characteristic feature of NEPC, potentially serving as a diagnostic marker via IHC.
- SMO loss may contribute to NEPC development by modulating AR signaling pathways.
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