Chemoresistance in Prostate Cancer Cells Is Regulated by miRNAs and Hedgehog Pathway

Abstract

Many prostate cancers relapse due to the generation of chemoresistance rendering first-line treatment drugs like paclitaxel (PTX) ineffective. The present study aims to determine the role of miRNAs and Hedgehog (Hh) pathway in chemoresistant prostate cancer and to evaluate the combination therapy using Hh inhibitor cyclopamine (CYA). Studies were conducted on PTX resistant DU145-TXR and PC3-TXR cell lines and clinical prostate tissues. Drug sensitivity and apoptosis assays showed significantly improved cytotoxicity with combination of PTX and CYA. To distinguish the presence of cancer stem cell like side populations (SP), Hoechst 33342 flow cytometry method was used. PTX resistant DU145 and PC3 cells, as well as human prostate cancer tissue possess a distinct SP fraction. Nearly 75% of the SP cells are in the G0/G1 phase compared to 62% for non-SP cells and have higher expression of stem cell markers as well. SP cell fraction was increased following PTX monotherapy and treatment with CYA or CYA plus PTX effectively reduced their numbers suggesting the effectiveness of combination therapy. SP fraction cells were allowed to differentiate and reanalyzed by Hoechst staining and gene expression analysis. Post differentiation, SP cells constitute 15.8% of total viable cells which decreases to 0.6% on treatment with CYA. The expression levels of P-gp efflux protein were also significantly decreased on treatment with PTX and CYA combination. MicroRNA profiling of DU145-TXR and PC3-TXR cells and prostate cancer tissue from the patients showed decreased expression of tumor suppressor miRNAs such as miR34a and miR200c. Treatment with PTX and CYA combination restored the expression of miR200c and 34a, confirming their role in modulating chemoresistance. We have shown that supplementing mitotic stabilizer drugs such as PTX with Hh-inhibitor CYA can reverse PTX chemoresistance and eliminate SP fraction in androgen independent, metastatic prostate cancer cell lines.

Enhanced expression of DNA polymerase eta contributes to cisplatin resistance of ovarian cancer stem cells

“…miR-93 is located at chromosome 7q22, in the intron 13 of the host gene minichromosome maintenance 7 (MCM7), where they are cotranscribed in the context of MCM7 primary transcript (39). Although MCM7 overexpression has been identified in various tumors and considered a bad prognostic indicator in prostate cancer (45,46), MCM7 expression is lower in various CSCs, including SP of human lung cancer cells (47) and prostate cancer cells (48), as well as ALDH+ breast cancer cells (41). In addition, an analysis of 12 publically available microarray datasets revealed a down-regulation of the MCM7 gene in various cancer stem-like cells in all datasets, although only three of them showed significant change (SI Appendix, Table S1).…”

Multifunctional Nanoparticles for Prostate Cancer Therapy

“…Cyclopamine is an inhibitor of the Sonic Hedgehog pathway responsible for the growth and proliferation of cancer stem cells. It has been used in the treatment of pancreatic cancer (9), glioblastoma multiforme (10), and prostate cancer (11). The use of cyclopamine in combination with paclitaxel for cancer stem cell therapy has also been reported (11).…”

“…It has been used in the treatment of pancreatic cancer (9), glioblastoma multiforme (10), and prostate cancer (11). The use of cyclopamine in combination with paclitaxel for cancer stem cell therapy has also been reported (11). The mechanism, by which cyclopamine acts, is disrupting the smoothened (Smo), a seven-transmembrane receptor, activity.…”

Role of miRNA and cancer stem cells in chemoresistance and pancreatic cancer treatment

“…Emerging evidence suggests dysregulation of certain miRNAs contributes to the generation of CSCs. Recent findings indicate an interrelationship between EMT phenotype, CSCs, chemoresistance and miRNAs ( Figure 1) [15]. Drug resistance positively correlates with the presence of CSCs, which in turn is linked to EMT phenotype acquisition.…”

“…Despite these advances, our understanding of chemoresistance in pancreatic cancer is fragmentary and incomplete. Recent studies in our lab and by other groups [2][3][4] have pointed to the important role played by microRNAs (miRNAs) and cancer stem cells (CSCs) in etiology and progression of various cancers, including pancreatic, marking their importance not only for diagnostics but also as potential targets for reversing drug resistance.…”