Identification of TP53 gene mutations in uterine corpus cancer with short follow-up

p53 is correlated with low BMI negative progesterone receptor status and recurring disease in patients with endometrial cancer

OBJECTIVE

P53 tumor suppressor gene plays a role in endometrial carcinogenesis. Former studies described correlations between p53 protein overexpression in endometrial cancer and prognostic factors, measured by immunohistochemistry. But data is still controversial. The aim of this study was to measure p53 and phospho-p53 overexpression by Western blot and evaluate correlations between overexpression and prognostic and clinical factors. Phospho-p53 seems to be the functional p53 protein and was examined for the first time in endometrial cancer.

METHODS

40 patients with endometrial cancer were included in the study. A control group of 20 patients with normal endometrial tissue samples was used. Western blot was performed for detection of p53 and phospho-p53. Clinical and pathological parameters were obtained from medical records. Statistical analysis was performed using the log-rank test, the Mann-Whitney test for two independent groups and the Fisher's exact test for dichotomous groupings.

RESULTS

In 17.5% of the patients with endometrial cancer a p53 overexpression could be evaluated. There was a correlation between a p53 overexpression and recurring disease (p: 0.014), a negative progesterone receptor status (p: 0.021) and a low BMI (p: 0.022). Only one of 40 patients had a phospho-p53 expression.

CONCLUSION

Western blot is a valid method for the detection of p53 overexpression. As other authors described before, p53 overexpression seems to correlate with negative prognostic factors. The correlation between p53 overexpression and a low BMI may underline the relationship between p53 alterations and biological aggressive endometrial carcinomas.

MicroRNAs and their target messenger RNAs associated with endometrial carcinogenesis

OBJECTIVE

Recent advances in gene expression technology have provided insights into global messenger RNA (mRNA) expression changes associated with endometrial cancer development. However, the post-transcriptional events that may also have phenotypic consequences remain to be completely delineated. MicroRNAs (miRNAs) are small non-coding RNA transcripts, that influence cell function via modulation of post-transcriptional activity of multiple target mRNA genes. Although recent reports suggest that miRNAs may influence human cancer development, their role in endometrial carcinogenesis remains to be described.

METHODS

We measured expression of 335 unique human miRNAs in 61 fresh-frozen endometrial specimens, including 37 endometrial cancers, 20 normal endometrium, and 4 complex atypical hyperplasia samples. In parallel, expression of 22,000 mRNA genes was analyzed using the Affymetrix Human U133A GeneChips in 29 of the endometrial samples, including 20 endometrial carcinomas and 9 normal endometrial samples. Differentially expressed mRNAs, miRNAs, and predicted miRNA-mRNA targets were integrated and evaluated for representation of relevant functional biologic pathways.

RESULTS

Thirteen miRNAs (p<0.02) and 90 mRNAs (FDR; 0%) were identified to be associated with endometrial cancer development. Twenty-six of the 90 (29%) differentially expressed mRNAs are Sangar-database predicted mRNA targets of the 13 miRNAs. Pathway analysis demonstrates significant involvement of these 26 mRNA genes in processes including cell death, growth, proliferation, and carcinogenesis.

CONCLUSION

We have identified miRNAs and mRNAs associated with endometrial cancer development. Further, our strategy of integrating miRNA/mRNA data may also aid in the identification of important biologic pathways and additional unique genes that have importance in endometrial pathogenesis.

Allelic loss at TP53 is not related to p53 protein overexpression in primary human endometrial carcinomas

We examined loss of heterozygosity (LOH) at the TP53 gene in primary human endometrial carcinomas (EC), and investigated the relationship between allelic loss, p53 protein overexpression, pRb-1 pathway alterations and MIB-1 proliferative activity. Applying the non-isotopic PCR-RFLP/VNTR-silver staining techniques, we investigated TP53 LOH in 46 tumors at four polymorphic loci. Out of 42 informative carcinomas, LOH was found in 19% of the cases studied. In general, there was no significant relationship between LOH and the clinical and pathological variables of cancer, including patient age, clinical stage, histological grade or depth of myometrial invasion. Interestingly, none of 7 tumors associated with hyperplasia revealed allelic imbalance, whereas 8 of 27 (30%) tumors without hyperplasia exhibited LOH (p=0.312; Fisher's exact test). Overexpression of nuclear p53 was not correlated with allelic loss at TP53 (p=0.336, Fisher's exact test). It is worth pointing out that p53 immunoreactivity was significantly related to proliferative activity of cancer (R=0.42, p=0.0037; Spearman's rank correlation test). A tendency towards a poorer outcome was reported in EC patients displaying TP53 LOH during short-time follow-up (p=0.093; log-rank test). None of the tumors simultaneously showed LOH at TP53 and RB1 genes (R=-0.211, p=0.16; Spearman's rank correlation test). p16INK4A alterations (LOH and gene deletion) occurred concomitantly, with 3 tumors showing the TP53 allelic loss, whereas the cyclin D1/cdk4 complex was overexpressed in a case with TP53 LOH. Altogether, losses at TP53 were not associated with p53 nuclear overexpression, but may affect a subset of EC patients characterized by an unfavorable prognosis at short-time follow-up. Allelic loss at TP53 seems to arise independently of LOH at the RB1 gene in carcinomas of the uterine corpus in humans. Disruptions at p16INK4A and/or cdk4/cyclin D1 concomitantly occurring with TP53 LOH may participate in the development of a subset of endometrioid-type ECs.

Association of p53 mutations and a codon 72 single nucleotide polymorphism with lower overall survival and responsiveness to adjuvant radiotherapy in endometrioid endometrial carcinomas

p53 Genetic alterations are associated with advanced stage and aggressive tumors in a variety of human malignancies. The aim of this study was to examine p53 for genetic alterations and to evaluate the association of these alterations with clinical outcome and response to adjuvant radiotherapy in endometrioid endometrial carcinomas. p53 mutations in exons 2-11 were assessed in 59 endometrioid carcinomas by polymerase chain reaction-single-strand conformational polymorphism and sequence analysis. Twelve mutations (20.3%) and nine polymorphisms were identified. Seven of the nine polymorphisms were codon 72 single nucleotide polymorphisms (SNP) with an Arg/Pro allelotype. Women harboring either a mutation or an Arg/Pro allelotype at codon 72 had a lower overall survival rate than women whose tumors lacked alterations in the p53 gene (P= 0.0029). Women were stratified based on p53 genetic alterations (p53 mutation or p53 codon 72 SNP) and whether or not they received adjuvant radiation therapy. Women with p53 genetic alterations who did not receive adjuvant radiotherapy had the lowest survival rate (P= 0.0005). Treated women with p53 genetic alterations and untreated women with no p53 alteration had similar rates of survival. Among women with p53 alterations, adjuvant radiotherapy substantially increased survival (P= 0.035). In multivariate analyses, the group of women with p53 genetic alterations who did not receive adjuvant radiation therapy had a 5.9-fold increased risk of death (95% confidence interval: 1.5-22.7) compared to women whose tumors lacked p53 alterations and did not receive adjuvant radiation therapy.

TP53 protein expression analysis by luminometric immunoassay in comparison with gene mutation status and prognostic factors in early stage endometrial cancer

Mutations in the TP53 tumor suppressor gene have been shown to significantly correlate with poor prognosis in endometrial cancer. In the present study we have evaluated a luminometric immunoassay (LIA) for quantitative estimation of TP53 protein expression in 65 cytosol preparations from endometrial cancer, previously analyzed for mutations in TP53 exons 4-10. LIA showed high (> or = 0.6 ng/mg protein) expression of TP53 protein in all eight tumors with missense mutation, but high protein levels were also detected in 15 tumors with normal TP53 sequence. All four tumors with nonsense or frameshift mutations had low or no TP53 protein expression. LIA was further evaluated in a retrospective study of 201 cytosol samples from endometrial cancer. TP53 overexpression (> = 0.6 ng/mg protein) was observed in 22% of the tumors and correlated with nonendometrioid histology types (P = 0.005), poorly differentiated tumors (P = 0.001), higher FIGO grade (P = 0.001), DNA nondiploidy (P = 0.002), and high S-phase fraction (P = 0.03). After a median follow-up time of 6.8 years (range 0.7-9.9 years), 22 (13%) progressions were observed in the 175 patients with early stage (I-II) disease. TP53 overexpression (P = 0.04), FIGO grade 3 vs. 1 + 2 (P = 0.01), higher age (P = 0.02), and DNA nondiploidy (P < 0.001) showed significant correlation to shorter progression-free survival in these patients. We conclude that TP53 protein analysis by LIA provides an incomplete correlation to mutation status and cannot substitute for mutation analysis in assessment of prognosis in endometrial carcinoma. In comparison to TP53 overexpression and higher FIGO grades, DNA nonploidy status seems to be a better prognostic indicator to define a subset of early stage endometrial cancer patients who may benefit by adjuvant chemotherapy/radiotherapy.

Distinct sets of gene alterations in endometrial carcinoma implicate alternate modes of tumorigenesis

BACKGROUND

Endometrial carcinomas seem to carry a different prognosis depending on the presence or absence of concomitant complex atypical hyperplasia (hyperplasia). The molecular genetic profile of these two pathogenetic types, based on the genes reportedly mutated in these cancers, remains to be defined. Although microsatellite inability is reported in approximately 25% of endometrial carcinomas, its relation with the 2 pathogenetic types is not investigated.

METHODS

To elucidate their underlying genetic changes, we analyzed 53 sporadic endometrial tumors, including 19 with and 34 without hyperplasia, for microsatellite instability (MSI), DNA ploidy (by flow cytometry), and for mutations in different genes.

RESULTS

Microsatellite instability was present in 21%, DNA nondiploidy in 15%, and mutations in the PTEN, KRAS, CTNNB1/beta-catenin, TP53, and CDKN2A genes were detected in 32, 11, 13, 17, and 0% of the tumors, respectively. Microsatellite instability and mutations in these genes were present in tumors both with and without complex atypical hyperplasia. All cases with complex atypical hyperplasia were early stage (I-II) endometrioid tumors and associated with long progression free disease (P = 0.0004). Furthermore, most tumors with hyperplasia had low World Health Organization or International Federation of Gynecology and Obstetrics grade, had less myometrial invasion, and showed expression of estrogen receptors. All MSI tumors were diploid and had a significantly higher rate of PTEN mutations, but similar rates of KRAS, beta-catenin, and TP53 mutations compared with microsatellite stable tumors. TP53 mutations more often were found in nondiploid tumors but never in tumors with PTEN, KRAS, or beta-catenin mutations, and all PTEN mutations occurred in diploid tumors.

CONCLUSIONS

Thus, PTEN, KRAS, beta-catenin, and TP53 mutations occurred in tumors both with and without hyperplasia, but PTEN and TP53 mutations were more common in tumors without hyperplasia. However, none of these genes seems to clearly distinguish tumors with and without hyperplasia, suggesting that other factors may be involved. Conversely, alterations in the PTEN and TP53 genes seem to define distinct subgroups of endometrial carcinoma, the former associated with diploidy and MSI, the latter with macroscopic chromosomal instability.

Urokinase plasminogen activator and its inhibitor, PAI-1, in association with progression-free survival in early stage endometrial cancer

Components of the urokinase plasminogen activator (u-PA) system are involved in the metastatic process, and have accordingly been associated with clinical outcome in a variety of malignant tumours. We investigated the prognostic importance of u-PA and plasminogen activator inhibitor type 1 (PAI-1) in endometrial cancer, analysed with luminometric immunoassay (LIA) and enzyme-linked immunosorbent assay (ELISA), respectively. Two different cut-off levels were used: the median and the 80th percentile-the latter because of the low progression rate for patients with early stage (I-II) endometrial cancer. After a median follow-up time of 6.8 years, univariate analysis of patients with stage I-II disease (n=188) showed that high u-PA and high PAI-1 content was associated with a shorter progression-free survival (PFS), but at different cut-off levels, uPA at the median (P=0.003), and PAI-1 at the 80th percentile (P<0.001). Among the other factors, DNA ploidy status was most strongly correlated to PFS, followed by age (continuous), International Federation of Gynaecology and Obstetrics (FIGO) grade of differentiation, S-phase fraction and progesterone receptor (PgR) status. Bivariate analyses, including ploidy and one of the factors u-PA or PAI-1, showed that both add significant prognostic information. We conclude that u-PA and PAI-1 are promising prognostic factors in early stage endometrial cancer.