Expression of p73 in colorectal carcinoma: clinicopathological relevance

p53-Related Transcription Targets of TAp73 in Cancer Cells-Bona Fide or Distorted Reality?

Identification of p73 as a structural homolog of p53 fueled early studies aimed at determining if it was capable of performing p53-like functions. This led to a conundrum as p73 was discovered to be hardly mutated in cancers, and yet, TAp73, the full-length form, was found capable of performing p53-like functions, including transactivation of many p53 target genes in cancer cell lines. Generation of mice lacking p73/TAp73 revealed a plethora of developmental defects, with very limited spontaneous tumors arising only at a later stage. Concurrently, novel TAp73 target genes involved in cellular growth promotion that are not regulated by p53 were identified, mooting the possibility that TAp73 may have diametrically opposite functions to p53 in tumorigenesis. We have therefore comprehensively evaluated the TAp73 target genes identified and validated in human cancer cell lines, to examine their contextual relevance. Data from focused studies aimed at appraising if p53 targets are also regulated by TAp73—often by TAp73 overexpression in cell lines with non-functional p53—were affirmative. However, genome-wide and phenotype-based studies led to the identification of TAp73-regulated genes involved in cellular survival and thus, tumor promotion. Our analyses therefore suggest that TAp73 may not necessarily be p53’s natural substitute in enforcing tumor suppression. It has likely evolved to perform unique functions in regulating developmental processes and promoting cellular growth through entirely different sets of target genes that are not common to, and cannot be substituted by p53. The p53-related targets initially reported to be regulated by TAp73 may therefore represent an experimental possibility rather than the reality.

TP73 is a credible biomarker for predicting clinical progression and prognosis in cervical cancer patients

Tumor protein p73 (TP73) has been reported to be dysregulated in various types of human cancer and associated with clinical progression and outcome. Owing to the lack of reports on the correlation between TP73 protein expression and clinicopathologic features of cervical cancer, the aim of our research was to explore the clinical and prognostic significance of TP73 protein expression in cervical cancer patients. In our study, TP73 protein expression was detected by immunochemistry in 118 paraffin-embedded cervical cancer tissue specimens and 40 paraffin-embedded normal cervical epithelium tissue specimens. In the results, we found cervical cancer tissues exhibited high TP73 expression in comparison with normal cervical epithelium tissues, which was consistent with the expression status of TP73 in The Cancer Genome Atlas (TCGA) database. Furthermore, we analyzed the relationships between TP73 expression and clinicopathologic features through using the chi-square test or Fisher’s exact test, and found high expression of TP73 was markedly associated with early clinical stage, less lymph node metastasis, absent distant metastasis, squamous cell carcinoma and favorable histological grade. The Kaplan–Meier method and log-rank test were performed based on the expression level of TP73 in a cervical cancer cohort from the TCGA database, and showed that TP73 expression was positively correlated with overall survival time in cervical cancer patients. Moreover, univariate and multivariate Cox proportional hazards regression model indicated that high TP73 expression was identified as an independent factor for predicting favorable overall survival in cervical cancer patients. In conclusion, TP73 expression is increased in cervical cancer tissues and cells, and acts as a credible biomarker for predicting favorable overall survival in cervical cancer patients.

p53, p63 and p73 expression and angiogenesis in keratocystic odontogenic tumors

Background

Keratocystic odontogenic tumors (KCOTSs) are odontogenic tumors previously referred to as odontogenic keratocysts. Several studies have reported that KCOT behavior is more like that of a benign neoplasm than a cyst. KCOTs are locally destructive and exhibit a high recurrence rate. The objective of this study is to characterize the expression of p53, p63 and p73 in KCOTs together with the relationship between their expression and KCOT angiogenesis and recurrence.

Material and Methods

Standard indirect immunohistochemistry using monoclonal antibodies specific to human p53, p63, p73 and CD105 was performed in formalin-fixed paraffin-embedded tissue sections of 39 KCOT samples. Grading of p53, p63 and p73 immunohistochemical staining was divided into three groups, whereas microvessel density (MVD) was presented as the mean +/- standard deviation. Associations between p53, p63 and p73 expression and clinical-pathological parameters were analyzed by Fisher’s exact test, whereas associations among MVD levels, clinical and pathological parameters and p53, p63 and p73 expression were analyzed by the Mann-Whitney U test. Correlations among p53, p63, p73 and MVD levels were analyzed using Spearman’s correlation coefficients. For all analyses, p< 0.05 was considered to indicate statistical significance.

Results

p53, p63 and p73 expression was noted in 23, 32 and 26 of 39 KCOT cases, respectively. The mean MVD was 26.7 ± 15.8 per high-power field. In addition, correlations between the expression levels of p53, p63, p73 and MVD in KCOT were examined. Statistically significant positive relationships were noted for all proteins (p<0.001).

Conclusions

Three members of the p53 protein family are expressed in KCOTs, and their expression relates to angiogenesis in these tumors.

Key words:p53, p63, p73, angiogenesis, keratocystic odontogenic tumors.

The prognostic value of p73 overexpression in colorectal carcinoma: a clinicopathologic, immunohistochemical, and statistical study of 204 patients

INTRODUCTION

The protein p73 is the first identified homolog of the tumor suppressor gene p53, but its function in tumor development has not been established. Indeed, the results regarding the p73 implication in colorectal cancers is still controversial.

AIM

We investigated whether the p73 is implicated in colorectal cancer, whether the p73 expression is related to prognosis and whether the p73 expression is correlated with p21-ras or p53.

MATERIALS AND METHODS

We performed a comparative immunohistochemical analysis of p73, p53, and p21ras proteins in primary colorectal tumor with matched normal mucosa and metastasis from 204 patients with colorectal cancer. We correlated these expressions with clinicopathologic variables and we compared the different profiles between nonmucinous carcinoma and mucinous carcinoma.

RESULTS

In this study, we did not find any correlation between p73 expression, sex, age, site, differentiation and stage. Overexpression of p73 was significantly correlated with infiltrating growth pattern (P<0.0001) and nonmucinous carcinoma (P<0.0001). Furthermore, frequency and intensity of p73 expression were marquedly increased from normal mucosa (26%), to primary tumors (75%) and to metastasis (97%). Furthermore, expression of p73 was also correlated with shorter survival period. The prognostic significance of p73 expression remained, even after adjustment for the clinical and pathologic variables. The p73 expression was positively correlated only with p21ras expression (P<0.0001).

CONCLUSIONS

All these findings prove that p73 expression should be considered as a valuable poor prognostic marker. Our data also suggest that TP73 gene may play a role in colorectal carcinoma development.

p63 and p73 expression in extrahepatic bile duct carcinoma and their clinical significance

p53 plays a pivotal role in the prevention of human tumor formation. p73 and p63 are new members of the p53 tumor suppressor family, which are becoming increasingly recognized as important players in human tumorigenesis. However, the roles of these proteins are not well elucidated in extrahepatic bile duct (EBD) carcinoma. We examined expressions of the p63 and p73 genes and proteins in normal biliary epithelia, biliary dysplasias, and EBD carcinomas using immunohistochemistry and RT-PCR analysis. p63 and p73 proteins were overexpressed in 26.3 and 41.0% of EBD carcinomas, respectively. p63 protein expression was more frequent in tumors with vascular invasion (P = 0.002) and distal location (P = 0.04), while p73 expression was more common in cancers with deeper tumor invasion (P = 0.04). Patients with tumors co-expressing both p63 and p73 were found to have a significantly worse overall survival rate compared to those with either p63 or p73 expression (P < 0.05) as determined in univariate and multivariate analyses. Our results strongly imply that the p53 family members have different functions in EBD carcinomas. Our data also indicate that interactions between p63 and p73 play an important role in tumorigenesis of EBD carcinoma.

The gastrin gene promoter is regulated by p73 isoforms in tumor cells

p73, a new p53 family member, is a transcription factor that is increasingly recognized in cancer research as an important player in tumorigenesis as well as in chemotherapeutic drug sensitivity. Despite the substantial structural and functional similarities to p53, accumulating evidence suggests that p53 and p73 may differently regulate their transcriptional targets. In this study, we have investigated the role of p73 in regulation of the gastrin gene promoter. Gastrin is a peptide hormone and an important factor in determining the progression of a number of human malignancies. Our results show that p73 can bind to the gastrin promoter. This leads to transcriptional upregulation of gastrin mRNA. We also found that the levels of gastrin and p73 transcripts correlate in primary gastric tumors. Taken together, our results demonstrate a novel mechanism for regulation of gastrin gene transcription and support a concept that p53 and p73 may have different biological roles in tumors.

Expression of p73 and c-Abl proteins in human ovarian carcinomas

The p73, a homologue of the p53 tumor suppressor protein, has a pro-apoptotic activity which is induced by the c-Abl, a protein tyrosine kinase appearing in the nucleus and cytoplasm of proliferating cells. However, the role of p73 and c-Abl in ovarian cancer is not well-defined. We investigated immunohistochemical expressions of p73 and c-Abl in 64 ovarian carcinomas, 13 borderline and 14 benign ovarian tumors to elucidate their clinicopathological relevances. Of the malignant, borderline, and benign ovarian tumors, respectively, 33 (51%), 10 (77%) and 13 (93%) had negative or low p73 expression, 31 (48%), 3 (23%) and 1 (7%) had high p73 expression, 23 (36%), 5 (38%) and 10 (71%) had negative or low c-Abl expression, and 41 (64%), 8 (61%) and 4 (29%) had high c-Abl expression. A high p73 or c-Abl expression was significantly associated with ovarian carcinomas as compared to benign tumors (p=0.003 and p=0.03 respectively). In addition, a significant correlation was found between the high p73 expression and disease stage (p=0.04) and patient's survival (p=0.02). No correlation was found with c-Abl expression. These results reveal an association of p73 overexpression with advanced ovarian carcinomas which may suggest the p73 overexpression as an indicator of poor prognosis.

No associations of p73 G4C14-to-A4T14 at exon 2 and p53 Arg72Pro polymorphisms with the risk of digestive tract cancers in Japanese

A case-control study was conducted to examine the possible association between digestive tract cancers and p73 G4C14-to-A4T14 at exon 2 and p53 Arg72Pro polymorphisms in Japanese. Cases were 102 esophageal cancer patients, 144 stomach cancer patients, and 147 colorectal cancer patients, and controls were 241 non-cancer outpatients. The genotype frequencies among controls were 55.3% for p73 GG at position 4, 40.4% for GA, and 4.3% for AA, and 37.7% for p53 ArgArg, 44.4% for ArgPro, and 18.0% for ProPro. No significant differences in the genotype frequencies were observed between the controls and each case group or cases as a whole.