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PubMed2006

PIK3CA mutations are an early genetic alteration associated with FGFR3 mutations in superficial papillary bladder tumors.

Bladder tumors constitute a very heterogeneous disease. Superficial tumors are characterized by a high prevalence of FGFR3 mutations and chromosome 9 alterations. High-grade and muscle-invasive tumors are characterized by Tp53 mutations and aneuploidy. We have analyzed the sequence of exons 9 and 20 of PIK3CA in a panel of bladder tumors covering the whole spectrum of the disease. DNA from formalin-fixed, paraffin-embedded tumor sections was amplified by PCR and products were sequenced. In an unselected panel of tumors representative of the disease, the PIK3CA mutation prevalence was 13% (11 of 87). Mutations occurred mainly at the previously identified hotspots (codons 542, 545, 1007, and 1047). The distribution according to stage was as follows: papillary urothelial neoplasms of uncertain malignant potential (PUNLMP; 11 of 43, 25.6%), T(a) (9 of 57, 16%), T(1) (2 of 10, 20%), and muscle-invasive tumors (0 of 20, 0%; P = 0.019). Mutations were associated with low-grade tumors: grade 1 (6 of 27, 22.2%), grade 2 (3 of 23, 13%), and grade 3 (2 of 37, 5.4%; P = 0.047). Overall, PIK3CA mutations were strongly associated with FGFR3 mutations: 18 of 69 (26%) FGFR3(mut) tumors were PIK3CA(mut), versus 4 of 58 (6.9%) FGFR3(wt) tumors (P = 0.005). Our findings indicate that PIK3CA mutations are a common event that can occur early in bladder carcinogenesis and support the notion that papillary and muscle-invasive tumors arise through different molecular pathways. PIK3CA may constitute a novel diagnostic and prognostic tool, as well as a therapeutic target, in bladder cancer.

Carcinoma, Papillary↗
PubMed2006

Mitotic arrest, apoptosis, and sensitization to chemotherapy of melanomas by methionine deprivation stress.

Methionine deprivation stress (MDS) eliminates mitotic activity in melanoma cells regardless of stage, grade, or TP53 status, whereas it has a negligible effect on normal skin fibroblasts. In most cases, apoptosis accounts for the elimination of up to 90% of tumor cells from the culture within 72 hours after MDS, leaving a scattered population of multinucleated resistant cells. Loss of mitosis in tumor cells is associated with marked reduction of cyclin-dependent kinase (CDK) 1 transcription and/or loss of its active form (CDK1-P-Thr(161)), which is coincident with up-regulation of CDKN1A, CDKN1B, and CDKN1C (p21, p27, and p57). Expression of the proapoptotic LITAF, IFNGR, EREG, TNFSF/TNFRSF10 and TNFRSF12, FAS, and RNASEL is primarily up-regulated/induced in cells destined to undergo apoptosis. Loss of Aurora kinase B and BIRC5, which are required for histone H3 phosphorylation, is associated with the accumulation of surviving multinucleated cells. Nevertheless, noncycling survivors of MDS are sensitized to temozolomide, carmustin, and cisplatin to a much greater extent than normal skin fibroblasts possibly because of the suppression of MGMT/TOP1/POLB, MGMT/RAD52/RAD54, and cMET/RADD52, respectively. Sensitivity to these and additional genotoxic agents and radiation may also be acquired due to loss of cMET/OGG1, reduced glutathione reductase levels, and a G(2)-phase block that is a crucial step in the damage response associated with enhancement of drug toxicity. Although the genes controlling mitotic arrest and/or apoptosis in response to low extracellular methionine levels are unknown, it is likely that such control is exerted via the induction/up-regulation of tumor suppressors/growth inhibitor genes, such as TGFB, PTEN, GAS1, EGR3, BTG3, MDA7, and the proteoglycans (LUM, BGN, and DCN), as well as the down-regulation/loss of function of prosurvival genes, such as NFkappaB, MYC, and ERBB2. Although MDS targets several common genes in tumors, mutational variability among melanomas may decide which metabolic and signal transduction pathways will be activated or shutdown.

Antineoplastic Agents↗
PubMed1997

Relationship between lifetime ovulatory cycles and overexpression of mutant p53 in epithelial ovarian cancer.

BACKGROUND: Several lines of evidence have suggested a relationship between a woman's number of ovulatory cycles and the development of ovarian epithelial cancer. Repair of the ovarian surface after ovulation requires cellular proliferation, and spontaneous mutations arising during the DNA synthesis that accompanies this proliferation may play a role in carcinogenesis. PURPOSE: We conducted a molecular epidemiologic study to test the hypothesis that a greater number of ovulatory cycles increases the risk of ovarian cancer by inducing proliferation-associated DNA damage. In particular, we examined the association between the lifetime number of ovulatory cycles and mutation of the p53 tumor-suppressor gene (also known as TP53) in ovarian tumors. METHODS: Case-case and case-control analyses involving participants in the Cancer and Steroid Hormone study were used to examine the association between p53 gene mutation in ovarian tumors and the lifetime number of ovulatory cycles. The women in our study were 20-54 years of age and included 197 case patients with invasive ovarian epithelial cancer and 3363 control subjects. Mutation of the p53 gene was indicated by overexpression of p53 protein (i.e., cellular accumulation of mutant p53 protein) in paraffin-embedded ovarian cancer tissue blocks; the mutant protein was detected by means of standard immunohistochemical techniques. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by employing multivariate analyses, with the use of logistic regression. Reported P values are two-sided. RESULTS: Women whose cancers overexpressed p53 protein (p53 positive) had a greater mean number of lifetime ovulatory cycles (388 +/- 77.4 cycles [mean +/- standard deviation]) than women whose cancers did not overexpress p53 protein (p53 negative) (342 +/- 119.0 cycles) (P = .0025). Furthermore, women with p53-positive tumors were more likely to have had moderate (i.e., 235-375) or high (i.e., 376-533) numbers of ovulatory cycles than women with p53-negative tumors (age-adjusted ORs = 7.0 [95% CI = 1.6-30.5] and 7.7 [95% CI = 1.4-41.2], respectively) (< or = 234 cycles was the referent category). After controlling for age, menopausal status, and nulliparity, women with p53-positive tumors were found to be significantly more likely to have had moderate or high numbers of ovulatory cycles than control subjects (ORs = 4.3 [95% CI = 1.4-13.0] and 9.1 [95% CI = 2.7-30.9], respectively); the corresponding ORs for women with p53-negative tumors compared with control subjects were 0.6 (95% CI = 0.3-1.4) and 1.3 (95% CI = 0.5-3.2), respectively. CONCLUSIONS AND IMPLICATIONS: A higher number of ovulatory cycles may be associated with increased amounts of proliferation-associated DNA damage and increased risk of developing p53-positive but not p53-negative epithelial ovarian cancer. Our results are consistent with more than one developmental pathway in the pathogenesis of this type of cancer.

Adult↗