Down-regulation of caspase 3 in breast cancer: a possible mechanism for chemoresistance

Abstract

Caspase-3 is a member of the cysteine protease family, which plays a crucial role in apoptotic pathways by cleaving a variety of key cellular proteins. Caspase-3 can be activated by diverse death-inducing signals, including the chemotherapeutic agents. The purpose of this study was to determine the levels of caspase-3 expression in breast tumor samples and to determine whether alterations in its expression can affect their ability to undergo apoptosis. Primary breast tumor and normal breast parenchyma samples were obtained from patients undergoing breast surgery and the expression of caspases-3 was studied. Similarly, normal mammary epithelial cells and several established mammary cancer cell lines were studied for caspases-3 expression by reverse transcriptase-polymerase chain reaction, Northern blot analysis, and Western blot analysis. Approximately 75% of the tumor as well as morphologically normal peritumoral tissue samples lacked the caspase-3 transcript and caspase-3 protein expression. In addition, the caspases-3 mRNA levels in commercially available total RNA samples from breast, ovarian, and cervical tumors were either undetectable (breast and cervical) or substantially decreased (ovarian). Despite the complete loss of caspase-3, the expression levels of other caspases, such as caspase-8 and caspase-9, were normal in all of the tumor samples studied. The sensitivity of caspase-3-deficient breast cancer (MCF-7) cells to undergo apoptosis in response to doxorubicin and other apoptotic stimuli could be augmented by reconstituting caspase-3 expression. These results suggest that the loss of caspases-3 expression may represent an important cell survival mechanism in breast cancer patients.

Death receptor 4 (DR4) efficiently kills breast cancer cells irrespective of their sensitivity to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)

“…Reconstitution of caspase 3 expression enhanced apoptosis induced by staurosporine and chemotherapeutic agents. 29,38 These data suggest that caspase 3 deficiency could at least partially account for resistance of MCF-7 cells to DR4. On the other hand, apoptosis induced by overexpression of the proapoptotic bcl-2 family member Bak was not impaired in MCF-7 cells as compared to the caspase 3-expressing HeLa cells.…”

“…However, this deficiency might not be restricted to MCF-7 cell line, as recent evaluation of caspase 3 mRNA and protein in primary breast tumors demonstrated lack of expression in 75% of the samples. 29 To determine whether the absence of caspase 3 expression in MCF-7 cells was unique, we evaluated expression of caspases in our panel of breast cancer cell lines by Western blotting. No caspase 3 protein was detected in MCF-7 cells, while all other cell lines expressed readily detectable level of protein (Fig 5b).…”

Old, new and emerging functions of caspases

“…156 CASP3 polymorphisms in some lung cancer patients also show significantly decreased risk of disease. 157 Although it was reported that caspase-3 expression is significantly reduced in breast cancer cells, cancer tissue and even in the normal parenchyma surrounding tumors, 158 several groups have demonstrated the converse. Higher levels of caspase-3 protein were found in malignant, compared to nonmalignant breast tissue, and coincided with increased apoptosis.…”

Evaluation of apoptotic cell death mechanisms induced by hypericin-mediated photodynamic therapy in colon cancer cells

“…Caspase-3 is a fundamental protein frequently used to investigate apoptotic pathways (Devarajan et al, 2002). During apoptosis, cytochrome-c (cyt-c) releases from mitochondria into the cytosol and induces the caspase activation pathway starting with procaspase-9 activation.…”