Expression of bax and p53 proteins in the tumorigenesis and progression of breast carcinomas

ERα and ERβ expression in correlation with Ki-67, Bcl-2 and Bak in primary tumors and lymph node metastases of breast cancer: The effect of pre-operative chemotherapy

This study aimed to assess the pre-operative chemotherapy impact on the relationship between estrogen receptor (ER) expression and markers of proliferation and apoptosis in primary and metastatic breast cancer. Immunohistochemical examinations were conducted on surgically removed ductal invasive breast cancers and their lymph node metastases in 135 patients. A total of 64 patients from this group underwent pre-operative chemotherapy and in 71 cases the surgery was performed without primary chemotherapy. A negative correlation between ERα and Ki-67 was found in primary tumors and lymph node metastases. A positive correlation was observed between ERα and Bcl-2. A positive correlation was also noted between ERβ and Bak, suggesting that the two ERs were involved in the regulation of proteins responsible for the control of the apoptotic process. Assessment of the expression of the proteins conducted separately in primary tumors and lymph node metastases did not reveal a significant effect of pre-operative chemotherapy on the correlations of ERs with Ki-67, Bcl-2 and Bak. However, the analysis of the correlations between the receptor expression in primary tumors and Ki-67, Bcl-2 and Bak in lymph node metastases showed a statistically significant impact of pre-operative chemotherapy on the correlations of ERα and Bcl-2 with ERβ and Bak, confirming involvement of the two ERs in the regulation of apoptosis during breast carcinogenesis.

Reduced mRNA and protein expression of BCL-2 versus decreased mRNA and increased protein expression of BAX in breast cancer brain metastases: a real-time PCR and immunohistochemical evaluation

OBJECTIVES

Brain metastases are an increasingly common complication in breast cancer patients. Apoptosis regulating genes are promising candidates for further treatment options. We examined the mRNA and protein expression of p53, BCL-2 and BAX in breast cancer brain metastases versus primary tumors.

METHODS

In a two-step approach p53, BCL-2 and BAX mRNA expression in ductal invasive breast cancer brain metastases was examined by: (1) reverse transcription-polymerase chain reaction (RT-PCR) mRNA expression screening (band appearance in relation to an internal standard) and (2) quantitative real-time RT-PCR (CT-values in relation to an internal standard). Protein expression using immunohistochemistry. Results were compared with primary tumors.

RESULTS

We found significantly lower BCL-2 mRNA and protein expression in breast cancer brain metastases versus primary tumors. P53 mRNA and protein expression was also lower in metastases. However, this difference was only significant on mRNA but not on the protein level. BAX expression evaluation revealed was contradictory results: mRNA expression was significantly lower whereas protein expression was significantly higher in metastatic lesions.

DISCUSSION

The mRNA and protein expression of p53 and BCL-2 seems to be reduced in breast cancer brain metastases. BAX mRNA and protein may be regulated differentially in metastatic lesions.

Dietary depletion of vitamin E and vitamin A inhibits mammary tumor growth and metastasis in transgenic mice

We showed previously that dietary antioxidant depletion enhances tumor reactive oxygen species (ROS) and apoptosis, resulting in a reduction in brain tumor size in the TgT(121) transgenic mouse model, a nonmetastatic tumor model. Here, in a transgenic mouse model of mammary tumorigenesis with defined rates of tumor growth and lung-targeted metastasis, we determined the ability of dietary antioxidant depletion to inhibit tumor growth and metastasis. Compared with control mice fed a standard diet, antioxidant-depleted mice exhibited tumor-targeted generation of ROS manifested by increased levels of oxidatively modified DNA/RNA (8- hydroxy-2'-deoxyguanine, 8-hydroxyguanine) and lipid peroxidation (4-hydroxy-2-nonenal) in primary and metastatic tumor foci. In addition to increased tumor-targeted ROS, the number of apoptotic cells was increased approximately 500% (P < 0.01) and terminal dUTP nucleotide DNA end-labeling-positive cells 200% (P < 0.01) in mice fed the antioxidant-depleted diet, whereas the percentage of tumor cells undergoing mitosis was >50% lower than in controls (P < 0.01). The proportional distribution of small (<1.5 cm) and large (> or = 1.5 cm) primary mammary tumors differed. The mice fed the antioxidant-depleted diet had more small primary tumors (P <0.05) and fewer large primary tumors (P < 0.05). Importantly, they also had fewer lung metastatic tumor foci compared with mice fed the control diet (4.5 +/- 1.3 vs. 15.8 +/- 8.5 foci/lung, P < 0.01). These findings may be important in understanding the role of dietary antioxidant vitamins in tumor growth and metastasis.