p53 tumor suppressor protein and tissue proliferative fraction in infiltrating duct carcinoma

Apoptosis in epithelial ovarian tumors

It is now recognized that apoptosis plays an important role in the pathogenesis of tumors. This study evaluated the extent of apoptosis in different grades of ovarian tumors and correlated it with the expression of apoptosis regulatory genes, p53 and bcl-2 and with the total proliferative compartment of the tumor defined by the expression of the proliferating cell nuclear antigen (PCNA). Apoptosis was evaluated by the TUNEL (Tdt-mediated dUTP biotin nick end labelling) assay. Expressions of p53, bcl-2 and PCNA were analyzed by immunohistochemistry. A negative correlation was observed between the expression of bcl-2 and the extent of apoptosis (r = -0.3336, p = 0.019). P53 accumulation directly correlated with the extent of apoptosis (r = 0.485, p = 0.00041). The labelling index of PCNA also showed correlation with expression of p53 (r = 0.49, p = 0.00000). Apoptosis was significantly higher in poorly differentiated tumors when compared to the well- and moderately-differentiated tumors (r = 0.49152, p = 0.00034). Such poorly-differentiated tumors also showed high p53 overexpression and loss of bcl-2 expression. The present study thus provides evidence that dysregulation of apoptosis and its regulatory genes is associated with increasing malignant potential and may thus contribute to the pathogenesis of ovarian tumors.

In situ apoptosis in the thyroid

Recent evidence has emphasized the importance of programmed cell death, or apoptosis, in the maintenance of tissue homeostasis and pathogenesis of tumors. This study analyzed the significance of apoptosis in relation to the expression of p53 and bcl-2 proteins, tissue proliferation defined by Ki-67 expression, and tissue histology in thyroid tissue. Extent of apoptosis was defined by morphological criteria and the terminal deoxynucleotidyl transferase-mediated deoxy uridine triphosphate (dUTP) biotin nick end labeling (TUNEL) assay. Immunocytochemistry was performed for p53, bcl-2, and Ki-67 expression. There was good correlation between TUNEL-reactive cells and morphological evaluation criteria for apoptosis. The extent of apoptosis was significantly associated with the type of thyroid lesion (r = 0.66990, p = 0.000012), both proliferative (namely multinodular goiter) and neoplastic (benign and malignant). A higher extent of apoptosis was evident in medullary and anaplastic carcinomas. Apoptosis also correlated to p53 protein accumulation (r = 0.485, p = 0.00041) and Ki-67 immunoreactivity (r = 0.435, p = 0.001). An inverse correlation was observed between bcl-2 expression and the extent of apoptosis (r = -0.33369, p = 0.01912). A direct correlation was also observed between p53 expression and Ki-67 immunoreactivity (r = 0.623, p = 0.0002). By inhibiting apoptosis, bcl-2, may cause a shift in tissue kinetics toward the preservation of genetically aberrant cells, thereby facilitating tumor progression. These results imply that rapidly proliferating tumors appear to have a high cell turnover state in which there may be increased chance of apoptosis among the proliferating cells. The ability of apoptosis to occur in the presence of a possibly mutant p53 protein suggest the existence of at least two p53 dependent apoptotic pathways, one requiring activation of specific target genes and the other independent of it. However, keeping in mind the limited number of subjects studied in each subgroup and the rather low correlation coefficients, these possibilities would have to be substantiated in a larger study population.

Angiogenesis during tumor progression in the oral cavity is related to reduced apoptosis and high tumor cell proliferation

Angiogenesis, the growth of new blood vessels, is believed to aid tumor progression and metastasis. Tumor progression is also influenced by the extent of proliferation and apoptosis. This study, therefore, analyzed in lesions of the oral cavity, the significance of angiogenesis in relation to apoptosis, expression of apoptosis regulatory p53, bax and bcl-2 proteins as well as tissue proliferation defined by cyclin D1 expression. Results from this study suggest that angiogenesis increases as histological abnormality increases in the oral mucosa. The expression of apoptosis regulatory proteins also appears to be altered in a histologically dependent manner. The correlation seen between CD34 expression, cyclin D1 and TUNEL reactive cells suggests that increased angiogenesis, decreased apoptosis and deregulated proliferation occur simultaneously during tumor progression in the oral mucosa. Presence of a mutant p53, increased bcl-2 expression and altered bax expression are also involved in this complex process.

Spontaneous programmed cell death in infiltrating duct carcinoma: association with p53, BCL-2, hormone receptors and tumor proliferation

Recent evidence has emphasized the importance of programmed cell death or apoptosis in the maintenance of tissue homeostasis and pathogenesis of tumors. This study, analyzed in breast cancer, investigates the significance of apoptosis in relation to the expression of p53 and bcl-2 proteins, tissue proliferation defined by Ki-67 expression, hormone receptors and tumor grade. The extent of apoptosis was defined by morphological criteria and the TUNEL (Tdt-mediated dUTP biotin nick end labelling) assay. Immunocytochemistry was performed for p53, bcl-2, estrogen receptor, progesterone receptor and Ki-67 expression. Mutant p53 protein was detected using a mutant specific ELISA. Immunoreactivity of p53 significantly correlated with the presence of mutant p53 protein detected by ELISA (r = 0.654, p = 0.00001). An inverse correlation was observed between bcl-2 expression and the extent of apoptosis (r = -0.33369, p = 0.01912). The extent of apoptosis directly correlated with p53 protein accumulation (r = 0.485, p = 0.00041), Ki-67 immunoreactivity (r = 0.435, p = 0.001), histopathological grade (r = 0.492, p = 0.0003), tumor size (r = 0.326, p = 0.023) and lymph node status (r = 0.287, p = 0.047). A direct correlation was also observed between p53 expression and Ki-67 immunoreactivity (r = 0.623, p = 0.0002). There was no statistically significant association between estrogen and progesterone receptor status and apoptosis. In addition, the TNM stage of the disease correlated with immunoreactivity of p53 (r = 0.572, p = 0.00012) and Ki-67 (r = 0.3744, p = 0.00818). Bcl-2, by inhibiting apoptosis, may cause a shift in tissue kinetics towards the preservation of genetically aberrant cells, thereby facilitating tumor progression. These results imply that rapidly proliferating tumors appear to have a high "cell turnover state" in which there may be an increased chance of apoptosis amongst the proliferating cells. The ability of apoptosis to also occur in the presence of mutant p53 protein suggests the existence of at least two p53-dependent apoptotic pathways, one requiring activation of specific target genes and the other independent of it.