Formation of nuclear Bax/p53 complexes is associated with chemotherapy induced apoptosis

Abstract

Mechanisms by which chemotherapeutic agents induce apoptosis are not completely understood. Current knowledge of the actual pharmacologic e ects of chemotherapy and their biochemical mechanisms are better understood than the downstream events, which initiate the apoptotic cascade. The chemotherapeutic agent cisplatin causes DNA damage and can induce apoptosis in several types of human cancers. We found the formation of previously unreported nuclear complexes between the tumor suppressor protein p53 and the proapoptotic protein Bax, in human melanoma cell lines induced into apoptosis following cisplatin exposure. These detergent resistant complexes were detected: after wild type (wt) p53 and Bax increased in the nucleus; at the same time when active cytoplasmic apoptosis related protease, caspase 3/CPP32 appeared; and prior to the detection of apoptotic DNA fragmentation. Three channel¯uorescence laser scanning confocal image microscopy revealed that the nuclear Bax/p53 complexes remained in the nucleus and localized proximal to DNA fragmentation sites as assayed by TUNEL after cisplatin exposure. Two human melanoma cell lines, expressing wt p53, were induced into apoptosis after cisplatin exposure, however they di ered in the timing of this induction. In both cell lines the formation of nuclear Bax/p53 coimmunoprecipitable complexes correlated with the timing of the induction of apoptosis. The degree of apoptosis induced by di erent concentrations of cisplatin correlated with the amount of nuclear Bax/p53 complexes. The coimmunoprecipitation of Bax and p53 was found regardless of the antibodies tested and was speci®c since Bcl-x L /p53 complexes were not detected. Additionally, the human prostate cancer cell line, LNCaP, also formed nuclear Bax/p53 complexes only after apoptosis was induced by paclitaxel. Oncogene (2000) 19, 6216 ± 6228.

Id-1 expression promotes cell survival through activation of NF-κB signalling pathway in prostate cancer cells

“…Since LNCaP harbours a functional p53 gene, we found that p53 protein expression was increased with increased TNFa concentrations (5 and 10 ng/ml) in all of the cell lines regardless of Id-1 levels (up to threefold, Figure 2a). Bax has been shown to be a downstream effector of the p53 protein in response to TNFa (Raffo et al, 2000). As shown in Figure 2b, after exposure to TNFa, Bax levels were greatly increased (4 -6-fold) in the controls, but the increment was much lower in the Id-1 transfectants (1.1-3.2-fold).…”

Mortalin–p53 interaction in cancer cells is stress dependent and constitutes a selective target for cancer therapy

“…[32][33][34] Neutralization of Hsp70 through antisense cDNA transfection resulted in tumor death, independent of p53 status. 35 Mortain-p53 interaction was shown to cause inactivation of both wild-type [19][20][21][22][23] and mutant p53 (Lu et al, data not shown) activities, including the deregulation of apoptosis in cancer cells by mechanisms involving formation of nuclear Bax/p53 complexes 36 and their crosstalk with nuclear chaperone, nucleophosmin. 37 Here, we showed that cancer cells under low stress did not have mortalin-p53 interaction and this was not due to their wild-type p53 status.…”

Bacterial cupredoxin azurin as an inducer of apoptosis and regression in human breast cancer

“…Cytosolic and mitochondrial fractions were prepared as described by Deveraux et al (1999). The nuclear extracts were separated following the procedure of Raffo et al (2000). For detection of caspase-7 and 9, the treated cells were lysed in lysis buffer containing 20 mM sodium phosphate (pH 7.4), 150 mM NaCl, 0.1% Triton X-100, and 10% glycerol supplemented with a protease inhibitor cocktail tablet.…”