Prognostic significance of p53 nuclear and cytoplasmic overexpression in right and left colorectal adenocarcinomas

Impacts of cytoplasmic p53 aggregates on the prognosis and the transcriptome in lung squamous cell carcinoma

The tumor suppressor TP53 gene, the most frequently mutated gene in human cancers, produces the product tumor protein p53, which plays an essential role in DNA damage. p53 protein mutations may contribute to tumorigenesis by loss of tumor suppressive functions and malignancy of cancer cells via gain-of-oncogenic functions. We previously reported that mutant p53 proteins form aggregates and that cytoplasmic p53 aggregates were associated with poor prognosis in human ovarian cancer. However, the prognostic impact of p53 aggregation in other tumors including lung squamous cell carcinoma (SCC) is poorly understood. Here, we demonstrated that lung SCC cases with cytoplasmic p53 aggregates had a significantly poor clinical prognosis. Analysis via patient-derived tumor organoids (PDOs) established from lung SCC patients and possessing cytoplasmic p53 aggregates showed that eliminating cytoplasmic p53 aggregates suppressed cell proliferation. RNA sequencing and transcriptome analysis of p53 aggregate-harboring PDOs indicated multiple candidate pathways involved in p53 aggregate oncogenic functions. With lung SCC-derived cell lines, we found that cytoplasmic p53 aggregates contributed to cisplatin resistance. This study thus shows that p53 aggregates are a predictor of poor prognosis in lung SCC and suggests that detecting p53 aggregates via p53 conventional immunohistochemical analysis may aid patient selection for platinum-based therapy.

Cytoplasmic p53 aggregates accumulated in p53-mutated cancer correlate with poor prognosis

Recent studies suggested that aggregates of mutant p53 proteins may propagate and impair normal p53 functioning in recipient cells. Our previous study showed that cancer cell-derived p53 aggregates that cells internalized interfered with p53-dependent apoptosis in recipient cells. However, involvement of p53 aggregate propagation in cancer pathology has not been fully elucidated. Here, we screened patients with high-grade serous ovarian carcinoma, which is characterized by an extremely high frequency of TP53 gene mutations, to show that patients with cytoplasmic p53 deposits have a poor prognosis compared with patients with complete p53 absence or strong nuclear p53 positivity. Cytoplasmic p53 in the patients with poor prognosis consisted of protein aggregates, which suggests that p53 aggregates are oncogenic drivers. Indeed, an inhibitor of p53 aggregation restored cellular apoptosis, a proper p53 function, in p53 aggregate-bearing patient-derived tumor organoids. In cell-based assays, endogenous and exogenous mutant p53 aggregates hindered chemotherapeutic activity of cisplatin, which depends on normal p53 functions. This inhibition was reduced by blocking p53 aggregation or internalization of p53 aggregates. Our study, thus indicates the involvement of p53 aggregate transmission in poor prognosis and in chemotherapy resistance in cancers.

Altered expression of p53, but not Rb, is involved in canine prostatic carcinogenesis

Abnormalities in the retinoblastoma (Rb) and p53 tumour suppressor gene have been frequently detected in human and canine cancers, but never investigated in canine prostate cancer, considered a good model for the advanced and aggressive androgen-resistant prostate cancer in men. Therefore, the aim of this study was to evaluate the immunohistochemical expression of Rb and p53 in 6 normal canine prostates, 15 canine prostates with benign prostatic hyperplasia (BPH) and 10 prostatic carcinomas (PCs). In all normal samples, p53 was expressed in low number of epithelial cells, while a greater number of positive cells were observed in BPH and PC. The mean number of positive cells was statistically significantly higher in PCs than normal and hyperplastic prostates. A cytoplasmic or nucleo-cytoplasmic staining was observed in 5 out of 10 PCs. Rb protein was expressed in high number of normal, hyperplastic and neoplastic cells without a statistically significant differences. Considering that Rb is frequently lost in human prostate cancer, we suggest that Rb is not involved in canine prostatic carcinogenesis. On the other hand, the increased expression of p53 that corresponds to genetic defects in the p53 gene may be associated with the malignant growth of canine prostate cancer, conferring an apoptosis-resistant phenotype.

Development and progression of colorectal neoplasia

A variety of genetic and molecular alterations underlie the development and progression of colorectal neoplasia (CRN). Most of these cancers arise sporadically due to multiple somatic mutations and genetic instability. Genetic instability includes chromosomal instability (CIN) and microsatellite instability (MSI), which is observed in most hereditary non-polyposis colon cancers (HNPCCs) and accounts for a small proportion of sporadic CRN. Although many biomarkers have been used in the diagnosis and prediction of the clinical outcomes of CRNs, no single marker has established value. New markers and genes associated with the development and progression of CRNs are being discovered at an accelerated rate. CRN is a heterogeneous disease, especially with respect to the anatomic location of the tumor, race/ethnicity differences, and genetic and dietary interactions that influence its development and progression and act as confounders. Hence, efforts related to biomarker discovery should focus on identification of individual differences based on tumor stage, tumor anatomic location, and race/ethnicity; on the discovery of molecules (genes, mRNA transcripts, and proteins) relevant to these differences; and on development of therapeutic approaches to target these molecules in developing personalized medicine. Such strategies have the potential of reducing the personal and socio-economic burden of CRNs. Here, we systematically review molecular and other pathologic features as they relate to the development, early detection, diagnosis, prognosis, progression, and prevention of CRNs, especially colorectal cancers (CRCs).

Influência da localização do tumor na expressão tecidual da proteína p53 em doentes com câncer colorretal: estudo de 100 casos

OBJETIVO: O objetivo do presente estudo foi verificar, se existem diferenças na expressão tecidual da proteína p53 segundo a localização do tumor em doentes com câncer colorretal. MÉTODO: Foram estudados 100 doentes (54 mulheres), com média de idade de 59,8 anos com adenocarcinoma colorretal. A expressão da proteína p53 foi analisada por imunoistoquímica, com anticorpo monoclonal anti-p53 pela técnica da estreptavidina-biotina-peroxidase. A expressão tecidual da proteína p53 foi relacionada às variáveis: gênero, idade, grau histológico, tipo histológico, tamanho do tumor, estadiamento TNM, profundidade de invasão da parede intestinal, comprometimento linfonodal, invasão angiolinfática, localização do tumor no intestino grosso em relação à flexura esplênica. Na avaliação estatística da relação entre expressão da proteína p53 e as variáveis consideradas empregou-se o teste qui-quadrado, estabelecendo-se nível de significância de 5% (p<0,05). RESULTADOS: A proteína p53 foi positiva em 77% dos casos. Com relação as diferentes variáveis consideradas verificou-se maior tendência de expressão da proteína mutante quando se considerava a idade (p=0,001), grau histológico (p=0,001), tipo histológico (p=0,001), estádios tardios da classificação TNM (p=0,001), maior profundidade de invasão na parede cólica (p=0,001), comprometimento linfonodal (p=0,001), invasão angiolinfática (p=0,02), localização após a flexura esplênica (p=0,001), não se encontrando relação com gênero (p=0,49) e tamanho do tumor (p=0,08). CONCLUSÃO: Os resultados do presente estudo permitem concluir que a expressão da proteína p53 mutante ocorre com maior freqüência nos tumores localizados a partir da flexura esplênica.

Colorectal cancer or colon and rectal cancer? Clinicopathological comparison between colonic and rectal carcinomas

AIMS

The aim of this study was to compare features of colon and rectal cancers such as prognosis, clinicopathological features and tumor markers, namely carcinoembryonic antigen (CEA), matrix metalloproteinase (MMP)-2 and p27(kip1).

METHODS

Two hundred and thirty patients with stage I-III colon or rectal cancer were retrospectively assessed with the endpoint of recurrence or metastasis after curative operation. CEA, MMP-2 and p27(kip1) were studied by immunohistochemistry in cancer tissues of all patients.

RESULTS

The disease-free 3-year survival rate after operation of the total 230 patients was 63.0%. The prognosis of colon cancer was significantly better than that of rectal cancer (70.6 vs. 57.0%; p = 0.017), especially for stage III (p = 0.0059). Multivariate analysis also demonstrated that tumor location in the colon or rectum, differentiation, venous invasion and the expression of CEA were independent factors for prognosis. The hazard of recurrence and metastasis in rectal cancer was 1.564 times that in colon cancer. In both groups, there were no statistical differences in age, gender, tumor size, tumor gross type, mucin production, tumor differentiation, venous invasion, MMP-2 and p27(kip1).

CONCLUSION

We investigated prognosis, clinicopathological factors, oncogenes and tumor suppressor gene production in colon and rectal cancers. The prognosis of colon cancer is better than that of rectal cancer, especially for stage III. This study shows some differences between colon and rectal cancer.

Aberrant p53 expression in feline vaccine-associated sarcomas and correlation with prognosis

Eighty spontaneously occurring feline vaccine-associated sarcomas (VAS) were evaluated to determine the immunohistochemical expression of the tumor suppressor gene p53. Sixty-five of 80 VAS (81%) exhibited positive immunoreactivity with Mab240, a murine monoclonal antibody that specifically recognizes mutated p53. Only 44 of 81 tumors (55%) were positive with rabbit polyclonal antibody CM-1. CM-1 often yielded nonspecific staining of nonneoplastic tissues. Nonspecific staining was greatly reduced or absent with Mab240. Cytoplasmic staining for p53 was a consistent pattern of VAS, occurring in 44% of tumors evaluated. Cats with tumors that exhibited cytoplasmic p53 had significantly shorter time to tumor recurrence compared to those cats with tumors that exhibited nuclear p53 staining (P = 0.0284), but no significant difference in survival outcome was observed. Immunohistochemical detection of p53 offers a prognostic tool for VAS, and, because abnormal p53 expression appears to be a common feature of feline VAS, molecular targeting of mutant p53, may offer a promising new therapeutic opportunity for this cancer.

Adjuvant treatment strategies for early colon cancer

Colon cancer remains a major cause of death; however, in the last 3 years a number of trials have been published that have led to changes in the treatment of patients with this disease. Initially, the adjuvant treatment of patients following curative resection was based on their Dukes staging; this is now being refined by consideration of other pathological factors, as well as the investigation of newer prognostic markers such as p53, Ki67 and a number of genes on chromosome 18. Tumours generally develop from the progressive accumulation of genetic events, although some develop through mutation or inactivation of DNA mismatch repair proteins leading to microsatellite instability; this is particularly important in Lynch's syndrome. The loss of gene expression can occur by deletion or mutation of genes or by aberrant methylation of CpG islands. In patients with Dukes C colon cancer the standard of care for adjuvant chemotherapy was previously based on bolus fluorouracil (5-fluorouracil) and folinic acid (leucovorin) administered 5 days per month or weekly for 6 months. Recent studies with a combination of infusional fluorouracil, folinic acid and oxaliplatin have been found to be superior. A further study replacing fluorouracil with oral capecitabine has also demonstrated equivalent disease-free survival. Although some debate remains regarding the benefit of adjuvant treatment for patients with Dukes B colon cancer, the emerging consensus is that, for those patients who are younger and have high-risk features, chemotherapy should be discussed. A number of large vaccine trials have also been conducted in the adjuvant setting and, overall, these have been disappointing. This is a rapidly advancing area of therapy and the results of new trials are awaited to determine whether additional benefits can be achieved with biological therapies such as anti-vascular endothelial growth factor and anti-epithelial growth factor receptor monoclonal antibodies, which have already been shown to be effective in setting of metastatic colon cancer.

The significance of tumor markers for proliferation and apoptosis in predicting survival in colorectal cancer

PURPOSE

Clinicopathologic staging is even today the best prognostic factor in both colon and rectal cancers. There is still considerable variation in survival within the stages. To find other prognostic indicators we investigated six biologic markers associated with apoptosis and cell proliferation.

METHODS

Formalin-fixed, paraffin-embedded tissue samples of 363 patients with primary colon or rectal cancer of Dukes Stages A to D were chosen for immunohistochemical staining of five tumor markers: bcl-2, p53, Ki-67, cyclin D1, and carcinoembryonic antigen. Also, the number of apoptotic cells was studied by the terminal deoxynucleotidyl transferase-mediated D: -UTP nick end labeling method in 347 cases. The study was done on specially prepared tissue arrays.

RESULTS

In rectal cancer, patients with a Ki-67 labeling index of 5 percent or higher had a better prognosis than those with a lower index. Also, positive cytoplasmic p53 expression predicted a favorable outcome in rectal cancer. In colon cancer, positive nuclear staining of cyclin D1 reflected better survival. Weak and moderate staining of carcinoembryonic antigen correlated with better prognosis than strong staining, but negative staining predicted poor outcome. High apoptotic index of 100 or higher correlated with poor prognosis in colon cancer. However, in rectal cancer, the trend was the opposite. Bcl-2 staining tended to be more intense in samples of patients living 5 years or longer compared with those with worse prognosis.

CONCLUSIONS

Colon cancer and rectal cancer seem to have different biologic behavior, at least with respect to apoptosis, cytoplasmic p53 expression, and perhaps Ki-67 and carcinoembryonic antigen. Further studies are needed to clarify the significance of these factors.

Different genetic features associated with colon and rectal carcinogenesis

PURPOSE

The issue of whether colon and rectal cancer should be considered as a single entity or two distinct entities is still debated, and there is a need to improve studies addressing the heterogeneity of the pathogenetic pathway leading to sporadic colorectal cancers (SCRCs) as well as to identify biological and/or molecular differences between colon and rectal cancers.

EXPERIMENTAL DESIGN

Specimens of SCRCs were analyzed for somatic mutations in APC, K-ras, and TP53 genes and loss-of-heterozygosity of chromosome 18.

RESULTS

Eleven SCRCs showed microsatellite instability. APC mutation frequency was significantly lower in microsatellite instability (MIN+) than in MIN- SCRCs. All MIN- SCRCs showed beta-catenin overexpression. A combined analysis of the biomarkers revealed two pathways mainly represented by MIN- SCRCs and differently followed on the basis of tumor location, APC-K-ras-TP53-Ch18q and APC-TP53-Ch18q.

CONCLUSIONS

The APC-beta-catenin pathway is inactivated in MIN- SCRCs and represents the first hit of SCRC development. Two preferential pathways followed by SCRCs occur, one K-ras dependent, in agreement with the Fearon and Vogelstein model, and the other K-ras independent. Significant differences between colon and rectal tumors occur in our series of MIN- SCRCs. The different pathways observed and their distribution can be summarized as follows: (a) K-ras mutations were more commonly detected in colon than in rectum; (b) the number of mutations detected was significantly higher in colon than in rectal tumors; and (c) a mutational pattern restricted to the APC gene was more common in rectal than in colon tumors. This molecular characterization can be translated into a clinical setting to improve diagnosis and to direct a rationale pharmacological treatment.

Two colons-two cancers: paradigm shift and clinical implications

Embryological and physiological data suggest that proximal (in relation to the splenic flexure) and distal parts of the colon represent distinct anatomical and functional entities. Since 1990, molecular biologists have identified two distinct pathways, microsatellite instability (MSI) and chromosomal instability (CIN), which are involved in the pathogenesis of colon cancer (CC). Thus, a new paradigm has emerged with the discovery that CC is a heterogeneous disease; furthermore recent data have demonstrated that these two distinct pathways in colorectal carcinogenesis are characterized by a different clinical outcome. The implications for the clinicians are twofold; (1) tumors originating from the proximal colon have a better prognosis due to a high percentage of MSI-positive lesions; and (2) location of the neoplasm in reference to the splenic flexure should be documented before group stratification in ongoing trials of adjuvant chemotherapy for CC. In the future, clinical decision-making regarding adjuvant chemotherapy might be stratified according to the MSI status of cancers located proximally to the splenic flexure.

Prognostic significance of p27(kip-1) expression in colorectal adenocarcinomas is associated with tumor stage

PURPOSE

Although the decreased expression of p27(kip-1), a cyclin-dependent kinase inhibitor, has been correlated with advanced tumor stage and short survival of patients with colorectal adenocarcinomas (CRCs), its prognostic value based on the tumor site, tumor stage, and patient ethnicity was not assessed. Therefore, in this study, we investigated whether the prognostic value of p27(kip-1) expression varies with the tumor site, tumor stage and patient ethnicity.

EXPERIMENTAL DESIGN

We evaluated 206 (85 African Americans and 121 Caucasians) archival tissue specimens of first primary CRCs for immunohistochemical expression of p27(kip-1), and its prognostic significance was analyzed using univariate Kaplan-Meier and multivariate Cox regression survival methods.

RESULTS

Although, similar proportion of CRCs with decreased p27(kip-1) expression was observed in all stages (range, 26-36%), the decreased p27(kip-1) expression has been shown as a marker of poor prognosis only for patients with stage III tumors both in univariate (log-rank test, P = 0.014) and multivariate (hazard ratio = 3.2, 95% confidence interval = 1.3-7.7; P = 0.01) survival analyses. The decreased expression of p27(kip-1) was associated with a high histologic grade (P = 0.016) in stage II CRCs, and with distal tumors (P = 0.001), tumor invasion (P = 0.044), and with local recurrence (P = 0.008) in stage III CRCs.

CONCLUSIONS

No prognostic significance was found for p27(kip-1) expression in stages I, II, or IV CRCs, and its prognostic value was not associated with either ethnicity or tumor location. These studies suggest that decreased expression of p27(kip-1) is an indicator of poor prognosis and aids in identifying a subset of patients with aggressive forms of stage III CRCs.

Prognostic value of proliferation, apoptosis, defective DNA mismatch repair, and p53 overexpression in patients with resected Dukes' B2 or C colon cancer: a North Central Cancer Treatment Group Study

PURPOSE

Molecular studies of colon cancer have provided insights into pathogenesis, yet it is unclear how important these markers are in predicting prognosis. This study investigated the prognostic significance of TUNEL, bcl-2, p53, proliferation marker Ki-67 and DNA mismatch repair (MMR) status in patients with Dukes' stage B2 and C colorectal adenocarcinomas.

PATIENTS AND METHODS

Tumor tissue from 366 patients (75% Dukes' C, 25% Dukes' B2) from four randomized North Central Cancer Treatment Group phase III surgical adjuvant trials were used. Eighty-one percent of patients received adjuvant treatment, which was primarily fluorouracil (FU) based (90%). Tumor location was predominantly (87%) the colon. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL), Ki-67, p53, bcl-2, and MMR were assayed using immunohistochemistry. Stage, grade, MMR, Ki-67, and previously determined flow cytometry markers (ploidy and S phase) were explored for associations with each other and with overall survival (OS) and disease-free survival (DFS).

RESULTS

Univariately, stage B2, low grade, diploid, Ki-67 more than 27%, normal p53, and FU-based adjuvant treatment were significantly associated with improved OS and DFS (P <.05). After adjusting for stage, grade, and ploidy in multivariate analysis, Ki-67 remained significantly related to both OS and DFS (P <.01). Active FU-based adjuvant treatment was significant only for OS in this multivariate model. Neither bcl-2 nor TUNEL were significant.

CONCLUSION

This retrospective study indicates that Ki-67 and ploidy may have stronger prognostic impact on OS and DFS than other parameters investigated after adjusting for stage and tumor grade. Prospective studies to elucidate the mechanism and prognostic significance of these findings are necessary.

Simultaneous detection of apoptosis and proliferation in colorectal carcinoma by multiparameter flow cytometry allows separation of high and low-turnover tumors with distinct clinical outcome

BACKGROUND

Dukes C colorectal carcinoma is treated with adjuvant chemotherapy. Adjuvant treatment is not standard for patients with Dukes B tumors, even though about 20% of patients within this tumor stage die of recurrent disease. The authors investigated whether a novel method of simultaneous detection of apoptosis and proliferation would improve the assessment of prognosis in colorectal carcinoma patients, with the ultimate goal of accurately identifying patients eligible for adjuvant therapy.

METHODS

A multiparameter flow cytometric assay with heat pretreatment was performed on 278 paraffin-embedded colorectal adenocarcinomas. After immunochemical isolation of tumor cells, apoptosis and proliferation were assessed simultaneously by immunostaining for the M30 antibody and by quantitative DNA analysis, respectively. Patients were followed for more than 10 years.

RESULTS

The mean values of apoptosis (apoptotic fraction [AF], i.e., the percentage of M30-positive cells) and proliferation (S-phase fraction [SPF]) were 11.1% and 13.1%, respectively. The AF and SPF values were correlated positively (P = 0.01) and both increased with advancing tumor stage (P = 0.02). Combining AF and SPF, patients with tumors with a high turnover (i.e., both AF and SPF values were greater than the mean) had an overall survival rate of 13%, whereas patients with low-turnover tumors (i.e., both AF and SPF values were less than the mean) had an overall survival rate of 89% (P < 0.001 by log rank test). Moreover, within Dukes B and C stages, patients with high-turnover tumors had a poorer survival than patients with low-turnover tumors (P < 0.001 for both stages).

CONCLUSIONS

The simultaneous detection of apoptosis and proliferation in archival material allows separation of high and low-turnover colorectal adenocarcinomas and improves the assessment of prognosis. This technique could be used to stratify patients for adjuvant chemotherapy.

TP53 mutation in colorectal cancer

Approximately half of all colorectal cancers show p53 (TP53) gene mutations, with higher frequencies observed in distal colon and rectal tumors and lower frequencies in proximal tumors and those with the microsatellite instability or methylator phenotypes. Alterations to this gene appear to have little or no prognostic value for colorectal cancer patients treated by surgery alone, but are associated with worse survival for patients treated with chemotherapy. There is some evidence that different p53 mutations are associated with different clinical features including prognosis and response to therapy, although further large studies are required to confirm this. Several in vitro, animal and clinical studies have shown that normal p53 is required for the response of colorectal cancers to 5-fluorouracil-based chemotherapy. This should be confirmed by additional retrospective cohort studies and by the incorporation of P53 status in ongoing and future clinical trials. The evaluation of p53 overexpression, using a standardized immunohistochemical (IHC) procedure, could be a clinically useful marker for the identification of colorectal cancer patients likely to benefit from the standard chemotherapy regime currently used for this disease.

Electrophilic prostaglandins and lipid aldehydes repress redox-sensitive transcription factors p53 and hypoxia-inducible factor by impairing the selenoprotein thioredoxin reductase

Tumor suppressor p53 exhibits an enigmatic phenotype in cells exposed to electrophilic, cyclopentenone prostaglandins of the A and J series. Namely, cells harboring a wild-type p53 gene accumulate p53 protein that is conformationally and functionally impaired. This occurs via an unknown molecular mechanism. We report that electrophilic cyclopentenone prostaglandins covalently modify and inhibit thioredoxin reductase, a selenoprotein that governs p53 and other redox-sensitive transcription factors. This mechanism accounts fully for the unusual p53 phenotype in cells exposed to electrophilic prostaglandins. Based on this mechanism we derived, tested, and affirmed several predictions regarding the kinetics of p53 inactivation; the protective effects of selenium; the structure-activity relationships for inhibition of thioredoxin reductase and impairment of p53 by electrophilic lipids; the susceptibility of hypoxia-inducible factor to inactivation by electrophilic lipids; and the equivalence of chemical inactivation of p53 to deletion of a p53 allele. Chemical precepts dictate that other electrophilic agents should also inhibit thioredoxin reductase and impair its governance of redox-sensitive proteins. Our results provide a novel framework to understand how endogenous and exogenous electrophiles might participate in carcinogenesis; how selenoproteins and selenium might confer protection against cancer; how certain tumors might acquire their paradoxical p53 phenotype; and how chronic inflammation might heighten the risk for cancer.

Have p53 gene mutations and protein expression a different biological significance in colorectal cancer?

p53 alterations are considered the most common genetic events in many types of neoplasms, including colorectal carcinoma (CRC). These alterations include mutations of the gene and/or overexpression of the protein. The aim of our study was to assess whether in 160 patients undergoing resective surgery for primary operable CRC there was an association between p53 mutations and protein overexpression and between these and other biological variables, such as cell DNA content (DNA-ploidy) and S-phase fraction (SPF), and the traditional clinicopathological variables. p53 mutations, identified by PCR-SSCP-sequencing analysis, were found in 68/160 patients (43%) and positive staining for p53 protein, detected with the monoclonal antibody DO-7, was present in 48% (77/160) of the cases, with agreement of 57% (91/160). In particular, a significant association was found between increased p53 expression and genetic alterations localized in the conserved regions of the gene or in the L3 DNA-binding domain and the specific type of mutation. Furthermore, both overexpression of p53 and mutations in the conserved areas of the gene were found more frequently in distal than in proximal CRCs, suggesting that they might be "biologically different diseases." Although p53 mutations in conserved areas were associated with flow cytometric variables, overexpression of p53 and mutations in its L3 domain were only related respectively to DNA-aneuploidy and high SPF. These data may reflect the complex involvement of p53 in the different pathways regulating cell-cycle progression. In conclusion, the combination of the mutational status and immunohistochemistry of p53, and flow cytometric data may provide an important insight into the biological features of CRCs.

Mechanisms of oncogenesis in colon versus rectal cancer

Observations support the theory that development of left- and right-sided colorectal cancers may involve different mechanisms. This study investigated different genes involved in oncogenesis of colon and rectal cancers and analysed their prognostic value. The study group comprised 35 colon and 42 rectal cancers. Rectal cancer patients had been treated with standardized surgery performed by an experienced rectal cancer surgeon. Mutation analysis was performed for p53 in eight colon cancers and for APC and p53 in 22 rectal cancers. MLH1, MSH2, Bcl-2, p53, E-cadherin and beta-catenin were investigated by immunohistochemistry in all colorectal tumours. APC mutation analysis of the MCR showed truncating mutations in 18 of 22 rectal tumours (82%), but the presence of an APC mutation was not related to nuclear beta-catenin expression (p=0.75). Rectal cancers showed significantly more nuclear beta-catenin than colon cancers (65% versus 40%, p=0.04). p53 mutation analysis corresponded well with p53 immunohistochemistry (p<0.001). Rectal cancers showed significantly more immunohistochemical expression of p53 than colon cancers (64% versus 29%, p=0.003). In rectal cancers, a significant correlation was found between positive p53 expression and worse disease-free survival (p=0.008), but not in colon cancers. Cox regression showed that p53-expression (p=0.03) was an independent predictor for disease-free survival in rectal cancers. This study concluded that rectal cancer may involve more nuclear beta-catenin in the APC/beta-catenin pathway than colon cancer and/or nuclear beta-catenin may have another role in rectal cancer independently of APC. The p53-pathway seems to be more important in rectal cancer, in which it also has independent prognostic value. When prognostic markers are investigated in larger series, differences in biological behaviour between colon and rectal cancer should be considered.

The results of colorectal cancer treatment by p53 status: treatment-specific overview

PURPOSE

Both negative and positive influences of mutant p53 on treatment outcome have been reported, and we present here a meta-analysis of published studies where outcome was reported for defined treatment groups.

METHODS

We identified articles on the effect of p53 status by treatment modality, excluding those not stratified by method of treatment. A common hazard ratio was estimated from studies that reported a multivariate analysis. We also estimated the numbers of patients expressing the endpoint at the mean or median follow-up time and calculated a pooled odds ratio.

RESULTS

Twenty-eight articles were evaluable (23 using immunohistochemistry to detect overexpression of p53 and 8 using DNA sequencing), for a total of 4,416 patients. For patients treated with surgery only, the immunohistochemistry studies showed a significant influence of p53 status on disease-free survival and a marginally significant influence on overall survival. In the studies using DNA sequencing, by contrast, there was a significant influence of p53 mutations on overall survival, but not disease-free survival. For patients treated with surgery and radiotherapy, the influence of p53 status on disease-free survival was either insignificant or marginally significant, depending on test used; there was no influence on overall survival.

CONCLUSIONS

Although this pooled analysis of published studies where treatment was accounted for shows that there is a borderline significant hazard associated with p53 overexpression or mutation vs. p53 wild-type, it is unlikely that p53 can be applied in a routine clinical setting alongside factors such as T stage, nodal status, and residual tumor, whose prognostic value is much stronger.

Bcl-2 expression is associated with improved prognosis in patients with distal colorectal adenocarcinomas

Several recent studies have suggested that the anatomic location of the tumor and ethnicity of the patient should be considered in the evaluation of prognostic markers of colorectal neoplasia. The phenotypic expression of Bcl-2 has been reported to be a useful prognostic marker in colorectal adenocarcinoma (CRC). However, its prognostic importance in CRCs based on their anatomic location and on the ethnicity of the patients has not been reported. Therefore, we evaluated Bcl-2 expression by immunohistochemistry in CRCs collected from 107 African-American and 149 Caucasian patients from a southern U.S. population. In univariate Kaplan-Meier survival analyses, Bcl-2 expression was associated with better overall survival of both African-American (log-rank, p = 0.040) and Caucasian (log-rank, p = 0.032) patients with distal but not with proximal CRCs. In multivariate Cox regression analyses, when the pathologic features of tumors were not included, the expression of Bcl-2 was associated with better survival in either ethnic patient populations with distal CRCs after adjusting for other confounding variables and p53(nac) status; however, it was not significant in either race when tumor stage was included in multivariate analyses. Thus, these studies suggest that the expression of Bcl-2 in CRCs is a valuable indicator of good prognosis in either race when CRCs are located in the distal colorectum. Also, these studies suggest that the expression of Bcl-2 is useful in determining prognosis before pathologic-clinical staging and it can aid in selection of treatment after evaluation of diagnostic biopsy specimens of patients with distal colorectal adenocarcinomas.

p53 status: an indicator for the effect of preoperative radiotherapy of rectal cancer

BACKGROUND

Rectal carcinoma is a common malignancy, with a history of high local recurrence rates following surgery. In recent years. preoperative radiotherapy and refined surgical technique have improved local control rates.

AIM

To investigate the relationship between expression of nuclear p53 protein and the outcome in rectal carcinoma, with and without short-term preoperative radiotherapy.

MATERIAL

Specimens from 163 patients from the Southeast Swedish Health Care region included in the Swedish rectal cancer trial between 1987-1990.

METHOD

New sections from the paraffin blocks of the preoperative biopsy and the surgical specimen were examined immunohistochemically using a p53 antibody (PAb 1801).

RESULT

Expression of nuclear p53 protein was seen in 41% of the tumours. The p53 negative patients treated with preoperative radiotherapy had a significant reduction of local failure compared with the non-irradiated p53 negative patients (P = 0.0008). In contrast, p53 positive patients showed no benefit from preoperative radiotherapy. The interaction between p53 status and the benefit of radiotherapy was statistically significant (P = 0.018).

CONCLUSION

Expression of nuclear p53 protein in rectal carcinoma seems to be a significant predictive factor for local treatment failure after preoperative radiotherapy. Further investigations are necessary to select patients for preoperative treatment based on analysis of the preoperative biopsies.

Nuclear accumulation of p53 in colorectal adenocarcinoma: prognostic importance differs with race and location of the tumor

BACKGROUND

Although several studies have been conducted to examine the role of p53 genetic abnormalities and their prognostic value in colorectal carcinoma, the incidence of nuclear accumulation of p53 and the prognostic importance of nuclear accumulation of p53 in African-American and white patients have not been investigated separately. Therefore, the authors evaluated the prognostic significance of p53 nuclear accumulation in these two racial groups.

METHODS

Nuclear accumulation of p53 was evaluated immunohistochemically in archival tissue specimens from 204 African-American and 300 white patients with primary colorectal adenocarcinomas who had undergone surgery. Survival times from colorectal adenocarcinoma were analyzed using Kaplan-Meier survival estimates and the Cox proportional hazards model for nuclear accumulation of p53 with adjustments for other confounding demographic and clinical variables.

RESULTS

Approximately equivalent proportions of distal (54%) and proximal adenocarcinomas (47%) were positive for nuclear accumulation of p53 in African-American patients. In contrast, distal colorectal adenocarcinomas from white patients more frequently were positive for nuclear accumulation of p53 than adenocarcinomas of the proximal colon (63% vs. 38%, respectively). Nuclear accumulation of p53 was found to be a strong predictor of poor survival in white patients (hazard ratio = 6.77; P = 0.0001) but not in African-American patients with primary adenocarcinomas of the proximal colon. Nuclear accumulation of p53 was not of prognostic value in patients of either race with primary adenocarcinomas of the distal colorectum.

CONCLUSIONS

Nuclear accumulation of p53 is a valuable indicator of poor prognosis only for white patients with adenocarcinomas of the proximal colon. The current study also suggests that the role of p53 dysregulation in colorectal adenocarcinomas may vary with the anatomic location of the tumor and the race of the patient. These findings suggest that the demographic characteristics of patients should be considered in the evaluation of prognostic markers of colorectal neoplasia.