Bim contributes to phenethyl isothiocyanate‐induced apoptosis in breast cancer cells

Abstract

Phenethyl isothiocyanate (PEITC) is a highly promising cancer chemopreventive constituent of cruciferous vegetables (e.g., watercress) with in vivo efficacy in experimental rodent cancer models. Research thus far implicates apoptosis induction in cancer chemopreventive response to PEITC, but the mechanism of proapoptotic effect is not fully understood. The present study demonstrates that p53 upregulated modulator of apoptosis (PUMA)-independent apoptosis by PEITC is mediated by B-cell lymphoma 2 interacting mediator of cell death (Bim). Exposure of a cell line (BRI-JM04) derived from spontaneously developing mammary tumor of a MMTV-neu transgenic mouse to pharmacological concentrations of PEITC resulted in decreased cell viability coupled with apoptosis induction, characterized by release of histone-associated DNA fragments into the cytosol and cleavage of poly-(ADP-ribose)-polymerase and procaspase-3. The PEITC-induced apoptosis in BRI-JM04 cells was associated with up-regulation of Bak, PUMA, and Bim (long and short forms of Bim), increased S65 phosphorylation of BimEL (extra-long form), and down-regulation of Bcl-xL and Bcl-2. On the other hand, a non-tumorigenic human mammary epithelial cell line (MCF-10A) was significantly more resistant to PEITC-induced apoptosis compared with BRI-JM04 despite induction of Bax and PUMA due to concomitant overexpression of anti-apoptotic proteins, including Bcl-xL, Bcl-2, and Mcl-1. Wild-type HCT-116 cells and its isogenic PUMA knockout variant exhibited comparable sensitivity to PEITC-induced apoptosis. On the other hand, siRNA knockdown of Bim protein imparted partial but statistically significant protection against PEITC-induced apoptosis in BRI-JM04, MCF-7, and MDA-MB-231 cells. In conclusion, the present study provides novel insight into the mechanism of PEITC-induced apoptosis involving Bim.

Differential induction of apoptosis in human breast cancer cell lines by phenethyl isothiocyanate, a glutathione depleting agent

“…Several previous studies have investigated effects of PEITC in breast cancer cells, demonstrating that PEITC induces apoptosis of human and mouse breast cancer cell lines in vitro (Hahm and Singh 2011;Lee and Cho 2008;Tseng et al 2004) and decreases breast cancer growth in vivo in a mouse model (McCune et al 2010). PEITC has also been shown to decrease expression and function of ER (ii) (iii) b Quantitation.…”

“…It is important to recognise that the differential induction of apoptosis in MDA-MB-231 and MCF7 cells is relative and not absolute. For example, PEITC has been shown to induce apoptosis in MCF7 cells in previous studies (Lee and Cho 2008;Hahm and Singh 2011). However, our study has focused on relatively early time points to probe some of the more immediate changes in PEITC-treated cells.…”

“…We analysed the effects of PEITC on expression of BAX, a pro-apoptotic BCL2 family protein which has previously been demonstrated to be increased in PEITC-treated in human ovarian and breast cancer cell lines (Hahm and Singh 2011;Lee and Cho 2008;Satyan et al 2006). An increase in BAX expression was observed at 2 h after addition of PEITC in MDA-MB-231 cells, and BAX levels further increased at 4 and 6 h (Fig.…”

“…PEITC has been shown to promote apoptosis in breast cancer cells (Hahm and Singh 2011;Lee and Cho 2008;Tseng et al 2004) and to decrease ER expression (Kang and Wang 2010). Induction of apoptosis has been associated with increased expression of the pro-apoptotic BAX and BIM proteins (Hahm and Singh 2011;Lee and Cho 2008;Tseng et al 2004). PEITC can also interfere with proangiogenic pathways via down-modulation of the HIF1α transcription factor (Wang et al 2009).…”

Phenethyl Isothiocyanate, a Dual Activator of Transcription Factors NRF2 and HSF1

“…In another study in human oral cancer cells (HN22), inhibition of p38 MAPK with the SB203580 p38 MAPK inhibitor blocked apoptosis mediated by PEITC's activation of the death receptor 5 (DR5) 84. Furthermore, it has been shown that compared to normal cells, cancer cells are more sensitive to PEITC‐mediated cell death 85. The seemingly conflicting evidence on the dependence of apoptosis on PEITC‐induced activation of specific MAPKs could be attributed to differences in the cancer cell lines used in these studies, including their individual MAPK and caspase status, and apoptotic susceptibility.…”