Involvement of the mitochondrial pathway in bruceine D-induced apoptosis in Capan-2 human pancreatic adenocarcinoma cells.
ABSTRACT The fruit of Brucea javanica L. is a common herb used in Chinese medicine for the treatment of a variety of cancers. Our research group has previously identified bruceine D (BD), a quassinoid found abundantly in B. javanica, to have potent cytotoxic effect on a number of pancreatic cancer cell lines, including Panc-1, SW1990 and Capan-1 cells. In the present study, we showed that BD was also able to inhibit the growth of the Capan-2 human pancreatic adenocarcinoma cell line, but it exerted only modest cytotoxicity on the WRL68 human hepatocyte cell line and a human pancreatic progenitor cell line. The antiproliferative effects of BD were comparable to those exhibited by camptothecin and gemcitabine in our culture system. We found a dose-dependent decrease of the mitochondrial membrane potential in BD-treated Capan-2 cells as measured by the JC-1 assay. BD exposure was able to attenuate the expression of Bcl-2 protein in Capan-2 cells as detected by western blot analysis. In addition, the expression of both caspase 9 and caspase 3 in BD-treated Capan-2 cells was significantly accentuated. Moreover, BD was capable of inducing the fragmentation of genomic DNA in Capan-2 cells as evidenced by Hoechst staining. Cell cycle analysis demonstrated that BD could increase the percentage of Capan-2 cells in the subG1 phase in a dose-related manner. An increase in the apoptosis of Capan-2 cells was also observed by Annexin V and PI staining. These results unequivocally indicate that BD induces cytotoxicity in Capan-2 cells via the induction of cellular apoptosis involving the mitochondrial pathway.
- [Show abstract] [Hide abstract]
ABSTRACT: Pancreatic cancer has a poor prognosis with a 5-year survival rate of <5%. It does not respond well to either chemotherapy or radiotherapy, due partly to cancer cell apoptotic resistance (AR). AR has been attributed to certain genetic abnormalities or defects in apoptotic signaling pathways. In pancreatic cancer, significant mutations of K-ras and p53, constitutive activation of NFκB, over-expression of heat shock proteins (Hsp90, Hsp70), histone deacetylase (HDACs) and the activities of other proteins (COX-2, Nrf2 and bcl-2 family members) are closely linked with resistance to apoptosis and invasion. AR has also been associated with aberrant signaling of MAPK, PI3K-AKT, JAK/STAT, SHH, Notch, and Wnt/β-catenin pathways. Strategies targeting these signaling molecules and pathways provide an alternative for overcoming pancreatic cancer AR. The use of herbal medicines or natural products (HM/NPs) alone or in combination with conventional anti-cancer agents has been shown to produce beneficial effects through actions upon multiple molecular pathways involved in AR. The current standard first-line chemotherapeutic agents for pancreatic cancer are gemcitabine (Gem) or Gem-containing combinations; however, the efficacy is dissatisfied and this limitation is largely attributed to resistance to apoptosis. Meanwhile, emerging data have pointed to a combination of HM/NPs that may augment the sensitivity of pancreatic cancer cells to Gem. Greater understanding of how these compounds affect the molecular mechanisms of apoptosis may propel development of HM/NPs as anti-cancer agents and/or adjuvant therapies forward. In this review, we give a critical appraisal of the use of HM/NPs alone and in combination with anti-cancer drugs. We also discuss the potential regulatory mechanisms whereby AR is involved in these protective pathways.The international journal of biochemistry & cell biology. 05/2014;