Enhancement of gemcitabine efficacy by K73-03 via epigenetically regulation of miR-421/SPINK1 in gemcitabine resistant pancreatic cancer cells

•The miR-421 expression was lower, and SPINK1 expression was higher in gemcitabine-resistant pancreatic cancer cells than in the pancreatic cancer.•MiR-421 has correlation with SPINK1 and miR-421 modulates the SPINK1 transcription.•SPINK1 play vital role to improve the mitochondrial function in the gemcitabine-resistant pancreatic cancer.•K73-03 alone or in combination with gemcitabine can induce mitochondrial damage and apoptosis in the gemcitabine-resistant pancreatic cancer cells.•K73-03 alone or in combination with gemcitabine can up-regulate miR-421 and down-regulate SPINK1 expressions in the gemcitabine-resistant pancreatic cancer cells.•K73-03 in combination with gemcitabine can improve gemcitabine efficacy and decreasing pancreatic cancer resistance. Gemcitabine (GCB) is a first-line chemotherapeutic drug for pancreatic cancer (PCa). However, the resistance begins developing within weeks of chemotherapy. SPINK1 overexpression enhances resistance to chemotherapy. In a recent study, our laboratory established that the oleanolic acid (OA) derivative, K73-03, had a strong inhibitory effect on a SPINK1 overexpressed PCa cells. In our current study, we studied the enhancement of GCB inhibitory effect by K73-03, a new novel OA derivative, alone or in combination with GCB on the GCB-resistant PCa cells by mitochondrial damage through regulation of the miR-421/SPINK1. We detected the binding between miR-421 and SPINK1-3′-UTR in GCB-resistant PCa cells using Luciferase reporter assays. Cells viability, apoptosis, migration, and mitochondrial damage were investigated. The results demonstrated that the combination of K73-03 and GCB suppressed the growth of AsPC-1 and MIA PaCa-2 cells synergistically, with or without GCB resistance. Mechanistic findings showed that a combination of K73-03 and GCB silences SPINK1 epigenetically by miR-421 up-regulating, which leads to mitochondrial damage and inducing apoptosis in GCB-resistant PCa cells. We found an interesting finding that the 73-03 in combination with GCB can improve GCB efficacy and decrease PCa resistance, which induced apoptosis and mitochondrial damage through epigenetic inhibition of SPINK1 transcription by miR-421 up-regulation. This was the first study that used OA derivatives on GCB-resistant PCa cells, so this combined strategy warrants further investigation. [Display omitted]