Key role of mitochondria in cerulenin-mediated apoptosis

Abstract

Cerulenin, a fungal metabolite, is known to be a specific inhibitor of fatty acid synthase. Here we report that cerulenin is an effective inducer of apoptosis in different wild-type p53 and mutant p53 tumor cell lines, whereas normal human keratinocytes and fibroblasts are resistant to the apoptotic effect. To get more insight into the mechanisms of how cerulenin induces apoptosis we investigated several signal transduction molecules, including p53, p73, p21/WAF1, Bax, cytochrome c, and caspases 3 and 9. Our data strongly indicate that mitochondria play a key role in the ceruleninmediated pathway. Bax overexpression correlated with the extent of apoptosis and appears to be regulated in a p53-independent manner. The significance of the mitochondrial pathway for the cerulenin-mediated apoptosis was confirmed by the rapid mitochondrial release of cytochrome c both in wild-type p53 and mutant cell lines. Interestingly, the rapid release of cytochrome c was not accompanied by a breakdown of the mitochondrial potential. Instead, the complete disruption of the mitochondrial function coincided with the appearance of a p18 kDa cleavage product of Bax.

Fatty acid synthase: a novel target for antiglioma therapy

“…To investigate further the apoptotic response, the role of the death receptor pathway in cerulenin-mediated apoptosis was evaluated by infecting glioma cells with a FADD-DN adenovirus. In agreement with the previously suggested mechanism involving cytochrome c release (Heiligtag et al, 2002) FADD-DN, which inhibits all the known death receptor pathways, had no effect on cerulenin-induced glioma cell death.…”

“…In our experiments, we demonstrated clearly that PARP cleavage, an apoptotic marker, was induced in cerulenin-treated U251 and SNB-19 cells; this was associated with significant cytotoxicity. Heiligtag et al (2002) reported that cerulenin is an effective inducer of apoptosis in WT or mutant p53 neuroblastoma, melanoma, and colon carcinoma cell lines; normal human cells were resistant to cerulenin-induced apoptosis. Further, apoptosis was mediated both by overexpression of proapoptotic Bax, in a p53-independent manner, and by a rapid release of mitochondrial cytochrome c, leading to activation of caspase 3 and 9.…”

Inhibition of fatty acid synthase in melanoma cells activates the intrinsic pathway of apoptosis

“…As p53 activation has been associated with the FASN inhibition-induced apoptosis in colon carcinoma, neuroblastoma, and breast cancer cell lines, 22,27 we sought to verify the effect of pifithrin-alpha, an inhibitor of p53 activation, on the apoptotic rates of B16-F10 cells. In the studied conditions, apoptosis was not prevented by p53 inhibition (Figure 5b), indicating that this tumor suppressor protein is not involved in the apoptosis triggered by the lack of an efficient endogenous fatty acid synthesis.…”

“…26 Mitochondrial involvement, evidenced by increased levels of the pro-apoptotic protein Bax and cytochrome c release, was shown in tumor cell lines following pharmacological FASN inhibition. 27,28 Despite the fact that the expression of a dominant-negative mutant p53 increases sensitivity of colon carcinoma cells to FASN inhibitors, 22 FASN inhibition-induced apoptosis was described as p53 independent. 27 Malignant melanoma is a chemotherapy-resistant aggressive tumor derived from melanocytes of the skin and, less frequently, oral mucosal membranes.…”

“…27,28 Despite the fact that the expression of a dominant-negative mutant p53 increases sensitivity of colon carcinoma cells to FASN inhibitors, 22 FASN inhibition-induced apoptosis was described as p53 independent. 27 Malignant melanoma is a chemotherapy-resistant aggressive tumor derived from melanocytes of the skin and, less frequently, oral mucosal membranes. In the last decades, its incidence is increasing in the United States, with more than 68 000 new cases estimated for 2009 according to American Cancer Society.…”