Apoptotic and antiproliferative effects of silk protein sericin conjugated-AgNO3 nanoparticles in human breast cancer cells

Bombyx mori silk sericin is a globular-like protein that is used as an antioxidant, antibacterial, and antitumor agent. In this current research, we isolated sericin by degumming process and formation of sericin-AgNO3 NPs confirmed by UV–vis spectra, SEM, EDX, FTIR, and XRD patterns. The sericin and sericin-AgNO3 NPs mediated changes in human breast cancer cells were determined. The antiproliferative activity of sericin-AgNO3 NPs was analyzed by MTT dye reduction assay. Alterations at molecular levels were investigated by qRT-PCR, while apoptotic effects were studied by nuclear DNA staining. After 72 h treatment, sericin and sericin-AgNO3 NPs showed significant antiproliferative effects in MDA-MB-231 (26 %) and MCF-7 (41 %) cells. Expression modification showed prominent stimulation of cell cycle arrest and stress related genes such as cyclin-dependent kinase inhibitors (CDKN1A, CDKN1B), and GADD family genes. RT-PCR results of the GADD family include GADD45A, B, G, 34, 153 and cyclin-dependent kinase inhibitors (CDKN1A, 1B) showed pronounced induction of 3.1 to 19.8-folds in MCF-7 cell line while induction in MDA-MB-231 cell line was 2.5 to 34.3-folds. Nuclear DAPI staining showed significant induction of apoptosis and nuclear fragmentation in MDA-MB-231 cells at a concentration of 1 mg/mL for both sericin and sericin-AgNO3 NPs. Meanwhile, in case of MCF-7 cells, after treatment with sericin and sericin-AgNO3 NPs (1 mg/mL), the cells changed into a round shape and lost their original spindle outlook in dose-dependent manners. We concluded that sericin-AgNO3 NPs have significant antiproliferative, apoptosis, and genetic profiling effects in both breast cancer cell lines at the highest concentration.