Transcriptome-Wide Effects of Sphingosine Kinases Knockdown in Metastatic Prostate and Breast Cancer Cells:
Heba Alshaker1,2, Qi Wang1, Daniel Brewer1,3
1School of Medicine, University of East Anglia, Norwich, United Kingdom.
Abstract:
Sphingosine kinases 1 and 2 (SK1 and SK2) are proto-oncogenic isozymes expressed in many human tumors and associated with chemoresistance and poor prognosis. They are well-recognized therapy targets and their inhibition was shown to induce tumor volume reduction and chemosensitization in multiple cancer models. Oncogenic signaling is extremely complex and often cross-regulated. Designing molecular therapies and their combinations requires rational approaches to avoid redundant targeting or developing resistance. In this study, we have performed RNA transcriptome microarray analysis of two breast and two prostate metastatic cancer cell lines treated with siRNAs targeting SK1 or SK2. In prostate cancer cell lines SK1 knockdown (KD) has significantly changed expression of several genes including downregulation of NSUN2, G3BP2 and upregulation of ETS1. SK2 KD also affected expression of multiple genes including downregulation of CAPZA1 NSUN3 and ADPGK and upregulation of VDAC1, IBTK, ETS1, and MKNK2. Similarly, in breast cancer cells SK1 KD led to downregulation of NSUN2, NFATC3, CDK2, and G3BP2 and upregulation of GTF2B, TTC17, and RAB23. SK2 KD in breast cancer cells has decreased expression of ITGAV and CAPZA1 and increased expression of GTF2B and ST13. Gene-set enrichment analysis of known biochemical pathways showed that in prostate and breast cell lines SKs KD have altered multiple pathways. SK1 KD altered chromatin assembly, regulation of G1/S transition and mitosis, Wnt and MAP kinase signaling and cell motility. SK2 KD altered RAS protein signal transduction, regulation of MAP kinase and serine/threonine kinase activity, cell motility, small GTPase mediated signal transduction and phosphatidylinositol 3-kinase (PI3K) signaling. Through genome-wide microarray analysis, we have identified important molecular pathways affected by SK1 and SK2 KD. It appears that while KD of both genes leads to a decrease in individual pro-tumorigenic genes, there is a universal cellular response resulting in upregulation of several known pro-survival and pro-tumorigenic pathways such as MAPK, RAS, and PI3K, which may mediate cancer resistance to anti-SKs therapies. Our data point out to the potential advantage of certain molecular therapy combinations in targeting prostate and breast cancer. Further signaling studies are required to confirm the individual involvement of identified pathways.
Insights
Targeting sphingosine kinases 1 and 2 (SK1 and SK2) in cancer may paradoxically activate pro-survival pathways. This study reveals that inhibiting SK1/SK2 in breast and prostate cancers can upregulate MAPK, RAS, and PI3K signaling, potentially causing therapeutic resistance.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Signaling
Background:
- Sphingosine kinases 1 and 2 (SK1 and SK2) are proto-oncogenic enzymes implicated in cancer progression, chemoresistance, and poor prognosis.
- SK1 and SK2 are recognized therapeutic targets, with inhibition showing promise in reducing tumor volume and enhancing chemosensitivity in preclinical models.
- Understanding the complex cross-regulation of oncogenic signaling is crucial for designing effective combination therapies and preventing resistance.
Purpose of the Study:
- To investigate the global gene expression changes and affected molecular pathways following SK1 and SK2 knockdown in metastatic breast and prostate cancer cell lines.
- To identify potential mechanisms of resistance that may arise from targeting SK1 and SK2.
Main Methods:
- RNA transcriptome microarray analysis was performed on two breast and two prostate cancer cell lines after siRNA-mediated knockdown of SK1 or SK2.
- Gene-set enrichment analysis was utilized to identify altered biochemical pathways.
Main Results:
- SK1 and SK2 knockdown significantly altered the expression of numerous genes in both prostate and breast cancer cell lines, including genes involved in cell cycle, signaling, and motility.
- SK1 knockdown affected pathways related to chromatin assembly, G1/S transition, mitosis, Wnt, and MAP kinase signaling.
- SK2 knockdown impacted pathways involved in RAS signaling, MAP kinase activity, cell motility, and PI3K signaling.
- Notably, knockdown of both SK1 and SK2 led to the upregulation of pro-survival pathways like MAPK, RAS, and PI3K, suggesting a potential compensatory mechanism.
Conclusions:
- Genome-wide analysis identified key molecular pathways modulated by SK1 and SK2 knockdown.
- Targeting SK1 and SK2 may trigger compensatory activation of pro-survival pathways (MAPK, RAS, PI3K), potentially mediating resistance to anti-SK therapies.
- These findings highlight the potential benefit of specific molecular therapy combinations for prostate and breast cancers and underscore the need for further signaling studies.
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