Role of Protein Kinase-C and Rho Kinase in the Cytotoxic Effects of Bitter Melon Extract on Metastatic Breast Cancer Cells


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Introduction: Bitter melon extract (BME) is known to inhibit breast cancer cells (MCF-7) proliferation. The PKC and ROK play critical roles in cell division, migration, and survival. However, the roles of protein kinase-c (PKC) and rho kinase (ROK) inhibition on MCF-7 cells have not been established. Moreover, whether potential effects of BME’s effects on MCF-7 cells are mediated by PKC and ROK are unknown. Aims: We aimed to investigate if BME exerts cytotoxic effects on breast cancer cells (MCF-7 cells) and if PKC and ROCK mediate BME’s effects. We hypothesized that BME inhibits proliferation of MCF-7 cells by decreasing PKC activity and increasing ROK activity. Methods: Fresh bitter melons were purchased from an Asian grocery store and the extract (BME) was extracted, centrifuged, and filter sterilized. The MCF-7 cells were cultured in DMEM medium with different amounts of BME [0%, 0.5%, 1%, 2%, 5%, and 10% of BME (v/v)], and in the presence of absence of PKC inhibitor (GF109203x; 0.5µM) and ROK inhibitor (H-1152; 1 µM). After culturing cells for 6 days (for the dose-response study) and 2 days (for the inhibitor studies), pictures of cultures were taken, cell viability was determined using Trypan blue dye, and change in protein expression was determined using western blotting. Repeated t-test was used to determine statistical significance. Results & Discussion: BME dose-dependently inhibited viability of MCF-cells (N=3) and MYPT1 (Myosin phosphatase targeting subunit-1) expression (N=1, duplicate). The PKC inhibitor alone did not have significant effect on cell viability (N=4) but the ROK inhibitor decreased cell viability (N=5) and MYPT1 expression. In the future, we will be studying phosphorylation of ROK’s target proteins to examine how ROK mediates BME’s cytotoxic effects.


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