PANC-1 cancer stem-like cell death with silybin encapsulated in polymersomes and deregulation of stemness-related miRNAs and their potential targets

Cancer stem cells (CSCs) have powerful self-renewal ability and tumor recurrence. Pancreatic ductal adenocarcinoma is a malignancy with high mortality rate and ˃5% survival. Silybin has anticancer and hepatoprotective properties. We loaded silybin in PEG400-OA (SPNs) and evaluated its cytotoxic effects on PANC-1 cells and PANC-1 CSCs.   Spheroids from PANC-1 cells were obtained by the hanging drop method. Anti-proliferative and apoptotic functions of SPNs were evaluated in spheroids and non-spheroids with MTT, DNA fragmentation, PI and PI/AnnexinV assays. The expression of CD markers was assessed with flow cytometry. QRT-PCR was used to evaluate the expression of some miRNAs and targets.    IC50 of SPNs was identified to be 50 µg/ml, 45 µg/ml, and 42µg/ml, respectively after 24 hr, 48 hr, and 72 hr in PANC-1 treated cells. PI staining and PI/AnnexinV assay showed that ~20%, ~60%, and ~80%, of cells treated with 30, 50, and 60 µg/ml of SPNs were in sub-G1 and apoptosis phase, respectively. DNA degradation was confirmed after SPNS stimulation. CD24, CD44, and CD133 expression decreased after SPNs treatment both in PANC-1 spheroid cells and PANC-1 cancer cell line. Under-expression of onco-miRs (miR-21, miR-155, and miR-221), over-expression of several apoptotic potential targets of oncomiRs (Bax, Casp-9, and P53), over-expression of tumor suppressive-miRs (let-7b, miR-34a, and miR-126), and under-expression of Bcl-2 was found in SPNs-treated cells.   We suggest that silybin encapsulated in polymersomes (SPNs) may be useful as a complementary agent for destroying both pancreatic cancer cells and pancreatic CSCs  along with chemotherapeutic agents.