Simultaneous mutations in K-ras and TP53 are indicative of poor prognosis in sporadic colorectal cancer

Osimertinib treatment response in a patient with lung adenocarcinoma harboring two rare EGFR mutations: A case report

Epidermal growth factor receptor (EGFR) mutations have emerged as the most well-studied oncogenic alterations in advanced non-small cell lung cancer. The presence of single common or rare EGFR mutations and extra complex EGFR mutations correlates with the response sensitivity to EGFR tyrosine kinase inhibitors. Therefore, given the lack of evidence for the emergence of rare EGFR mutation types, the pathogenic mechanisms of uncommon EGFR mutations and the optimal treatment strategies remain to be explored further. The present study describes the case of a patient diagnosed with lung adenocarcinoma (LUAD) carrying two rare EGFR exon 18 indel/G719C and exon 19 L747S mutations, in which persistent lesion shrinkage was exhibited within 16 months of osimertinib treatment. Given the paucity of clinical trials for the treatment of LUAD harboring complex EGER mutations, the present detailed case description may provide clinicians with effective clinical experience in treating patients.

Role of RAS mutation status as a prognostic factor for patients with advanced colorectal cancer treated with first-line chemotherapy based on fluoropyrimidines and oxaliplatin, with or without bevavizumab: A retrospective analysis

The role of Kirsten rat sarcoma viral oncogene homolog (KRAS) and neuroblastoma RAS viral oncogene homolog (NRAS) mutations as negative predictors for anti-epidermal growth factor receptor (EGFR) therapies in metastatic colorectal cancer (CRC) has been firmly established. However, whether the RAS mutation status plays a role as a biomarker for anti-vascular endothelial growth factor (VEGF) treatment remains controversial. Data from 93 CRC patients who received first-line cytotoxic chemotherapy with fluoropyrimidines and oxaliplatin, with or without bevacizumab, were analyzed. We investigated the association between the RAS mutation status and clinical outcomes in terms of response rate, progression-free survival (PFS) and overall survival (OS). Mutations in RAS genes were observed in 47 (52.6%) patients (45 KRAS and 2 NRAS mutations). Patients with tumours harbouring RAS mutations were less suitable for primary tumour resection, were more likely to develop lung metastases, and received bevacizumab treatment for a shorter time period compared with those with wild-type tumours. The response rate to chemotherapy did not differ according to the RAS mutation status, and there were no significant differences in PFS [RAS mutation: 12 months, 95% confidence interval (CI): 8.7-15.2 vs. RAS wild-type: 12 months, 95% CI: 9.67-14.32; P=0.857] or OS (RAS mutation: 20 months, 95% CI: 14.3-25.6 vs. RAS wild-type: 24 months, 95% CI: 18.7-29.2; P=0.631). Patients with RAS mutation vs. those with RAS wild-type exhibited a favourable trend in PFS when treated with bevacizumab (13 months, 95% CI: 6.5-19.4 vs. 10 months, 95% CI: 4.2-15.7, respectively; P=0.07) and OS (27 months, 95% CI: 18.5-35.4 vs. 15 months, 95% CI: 12.4-17.5, respectively; P=0.22). In conclusion, RAS mutations are not a prognostic marker for PFS and OS in CRC patients receiving fluoropyrimidine-oxaliplatine treatment, with or without bevacizumab. RAS mutations are not predictive of the lack of efficacy of bevacizumab, and these patients appear to benefit from anti-angiogenic treatment.

Genetic markers of recurrence in colorectal cancer

Colorectal cancer (CRC) worldwide belongs to one of the most frequent cancers affecting both genders. Surgery and 5-fluorouracil-based adjuvant chemotherapy are recommended for patients with high-risk stage II and stage III colon carcinoma. Mutations of genes encoding for specific proteins may have an impact on the time to recurrence. These proteins act over specific signaling pathways, are implicated in metabolic processes and regulate the cell cycle. Though many retrospective studies show strong associations between genetic mutations and the clinical outcome of patients with CRC, currently no validated biomarkers are used in clinical routine settings. Therefore, large prospective validation studies should be carried out in order to strengthen the position of genetic mutations in personalized treatment of patients with CRC.

Can Serum be Used for Analyzing the KRAS Mutation Status in Patients with Advanced Colorectal Cancer?

Purpose

KRAS mutations have been used widely as prognostic or predictive marker in patients with advanced colorectal cancer (CRC). However, it may be difficult to obtain a tumor tissue for analyzing the status of KRAS mutation in large proportion of patients with advanced disease.

Materials and Methods

We obtained pairs of tumor and serum samples from 65 patients with advanced CRC, between March 2008 and July 2011. KRAS mutation status from the tumor samples was analyzed by genomic polymerase chain reaction and direct sequence, and KRASmutation status from the serum samples was determined by a genomic polymerase chain reaction–restriction fragment length polymorphism assay.

Results

KRAS mutations were detected in the serum samples of 26 patients and in the tumor samples of 31 patients. KRAS mutation status in the serum and tumor samples was consistent in 44 of the 65 pairs (67.7%). There was a significant correlation between the mutations detected in the serum sample and the mutations detected in the matched tumor sample (correlation index, 0.35; p < 0.004). Twenty-two of the 57 patients (38.5%) received anti-epidermal growth factor receptor therapy as any line therapy. There was no significant difference in the overall survival (OS) in accordance to the status of KRASmutations in both the serum and tumor samples (p > 0.05). In a multivariate analysis, liver metastasis and no cytoreductive operation were independent prognostic factors for decreased OS.

Conclusion

The serum sample might alternatively be used when it is difficult to obtain tumor tissues for analyzing the status of KRAS mutation in patients with advanced CRC.

The BRAF mutation is associated with the prognosis in colorectal cancer

BACKGROUND

Two members of the Ras/Raf signaling pathway, KRAS and B-raf, are suspected to be involved in the stepwise progression of colorectal cancer (CRC) tumorigenesis.

OBJECTIVE

We compared the KRAS and BRAF mutation status of CRC patients with their clinicopathological characteristics and examined the effect of mutation status on survival rates.

METHODS

DNA was extracted from 164 samples, and the mutation statuses of KRAS and BRAF were assessed using peptide PNA clamp real-time PCR method. The presences of mutation were compared with clinicopathological factors and 5-year survival rate.

RESULTS

Among the 164 CRC cases, KRAS mutation as detected in 71 cases (43.3 %), respectively, with no relationship with clinicopathological factors of the patients. On Kaplan-Meier survival analysis, KRAS mutation was not significantly associated with survival (p = 0.971). BRAF mutation was detected in 26 cases (15.9 %) and not associated with clinicopathological factors of the patients. However, the 5-year survival rate of BRAF mutations was significantly decreased (p = 0.02).

CONCLUSIONS

The presence of KRAS mutation did not correlate with the various clinicopathological factors of CRC patients or the survival rate. However, the survival rate was reduced in BRAF-mutated CRC patients. Therefore, BRAF mutation could be an important prognostic factor in CRC patients.

Biomarkers in precision therapy in colorectal cancer

Colorectal cancer (CRC) is the most commonly diagnosed cancer in Europe. Because CRC is also a major cause of cancer-related deaths worldwide, a lot of research has been focused on the discovery and development of biomarkers to improve the diagnostic process and to predict treatment outcomes. Up till now only a few biomarkers are recommended by expert panels. Current TNM criteria, however, cause substantial under- and overtreatment of CRC patients. Consequently, there is a growing need for new and efficient biomarkers to ensure optimal treatment allocation. An ideal biomarker should be easily translated into clinical practice, to identify patients who can be spared from treatment or benefit from therapy, ultimately resulting in precision medicine in the future. In this review we aim to provide an overview of a number of frequently studied biomarkers in CRC and, at the same time, we will emphasize the challenges and controversies that withhold the clinical introduction of these biomarkers. We will discuss both prognostic and predictive markers of chemotherapy, aspirin therapy as well as overall therapy toxicity. Currently, only mutant KRAS, mutant BRAF, MSI and the Oncotype DX® Colon Cancer Assay are used in clinical practice. Other biomarker studies showed insufficient evidence to be introduced into clinical practice. Divergent patient selection criteria, absence of validation studies and a large number of single biomarker studies are possibly responsible. We therefore recommend that future studies focus on combining key markers, rather than analysing single markers, standardizing study protocols, and validate the results in independent study cohorts, followed by prospective clinical trials.

Impact of KRAS Mutation Status on Outcomes in Metastatic Colon Cancer Patients without Anti-Epidermal Growth Factor Receptor Therapy

Purpose

Activating mutation of the KRAS oncogene is an established negative predictor for anti-epidermal growth factor receptor (anti-EGFR) therapies in metastatic colorectal cancer (CRC). However, KRAS mutation as a prognostic factor of survival outcome remains controversial in CRC, independent of anti-EGFR therapies.

Materials and Methods

We conducted a retrospective analysis of 103 CRC patients who were available for evaluation of KRAS mutation status. None of the patients analyzed had received anti-EGFR therapies. The role of KRAS mutation status was evaluated as a predictive factor for oxaliplatin or irinotecan and as a prognostic factor in CRC patients who did not receive anti-EGFR therapies.

Results

Mutations in KRAS were observed in 48.5% of patients. The response for oxaliplatin- (p=0.664) and irinotecan-based (p=0.255) cytotoxic chemotherapy did not differ according to the KRAS mutation status. In addition, no significant difference in progression free survival (PFS; oxaliplatin, p=0.583 and irinotecan, p=0.426) and overall survival (OS; p=0.258) was observed between the wild and mutant type of the KRAS gene. In univariate and multivariate analyses, KRAS mutations did not have a major prognostic value regarding PFS (oxaliplatin: hazard ratio, 0.892; 95% confidence interval [CI], 0.590 to 1.347; p=0.586 and irinotecan: hazard ratio, 0.831; 95% CI, 0.524 to 1.319; p=0.433) or OS (hazard ratio, 0.754; 95% CI, 0.460 to 1.236; p=0.263). In addition, anti-vascular endothelial growth factor therapies did not affect PFS to oxaliplatin or irinotecan and OS.

Conclusion

KRAS mutation is not a prognostic marker for PFS to oxaliplatin or irinotecan and OS in CRC patients who did not receive anti-EGFR therapies.

Role of Kras status in patients with metastatic colorectal cancer receiving first-line chemotherapy plus bevacizumab: a TTD group cooperative study

BACKGROUND

In the MACRO study, patients with metastatic colorectal cancer (mCRC) were randomised to first-line treatment with 6 cycles of capecitabine and oxaliplatin (XELOX) plus bevacizumab followed by either single-agent bevacizumab or XELOX plus bevacizumab until disease progression. An additional retrospective analysis was performed to define the prognostic value of tumour KRAS status on progression-free survival (PFS), overall survival (OS) and response rates.

METHODOLOGY/PRINCIPAL FINDINGS

KRAS data (tumour KRAS status and type of mutation) were collected by questionnaire from participating centres that performed KRAS analyses. These data were then cross-referenced with efficacy data for relevant patients in the MACRO study database. KRAS status was analysed in 394 of the 480 patients (82.1%) in the MACRO study. Wild-type (WT) KRAS tumours were found in 219 patients (56%) and mutant (MT) KRAS in 175 patients (44%). Median PFS was 10.9 months for patients with WT KRAS and 9.4 months for patients with MT KRAS tumours (p=0.0038; HR: 1.40; 95% CI:1.12-1.77). The difference in OS was also significant: 26.7 months versus 18.0 months for WT versus MT KRAS, respectively (p=0.0002; HR: 1.55; 95% CI: 1.23-1.96). Univariate and multivariate analyses showed that KRAS was an independent variable for both PFS and OS. Responses were observed in 126 patients (57.5%) with WT KRAS tumours and 76 patients (43.4%) with MT KRAS tumours (p=0.0054; OR: 1.77; 95% CI: 1.18-2.64).

CONCLUSIONS/SIGNIFICANCE

This analysis of the MACRO study suggests a prognostic role for tumour KRAS status in patients with mCRC treated with XELOX plus bevacizumab. For both PFS and OS, KRAS status was an independent factor in univariate and multivariate analyses.

Is K-ras gene mutation a prognostic factor for colorectal cancer: a systematic review and meta-analysis

BACKGROUND

: The K-ras gene is one of the commonly mutated oncogenes associated with colorectal cancer. However, its prognostic significance for patients with colorectal cancer remains inconclusive.

OBJECTIVE

: To derive a more precise estimation of the prognostic significance of K-ras gene mutations, a systematic review and meta-analysis were performed.

DATA SOURCES

: We searched PubMed, Embase, and the Cochrane databases from January 1992 to November 2011.

STUDY SELECTION

: The prognostic value of K-ras gene mutations was examined in patients with colorectal cancer who did not receive preoperative chemotherapy or radiation.

MAIN OUTCOME MEASURES

: The effect of K-ras gene mutations on the overall survival was measured by the HR and 95% CIs.

RESULTS

: The pooled HR for the association between K-ras gene mutations and overall survival in patients with colorectal cancer was 1.04 (95% CI: 0.99-1.10, p = 0.11). Subgroup analysis showed significant reductions in the overall survival associated with mutations at K-ras codon 12, the articles that reported HR directly, and the studies published before and after 2005, although publication bias was present. All the associations disappeared after adjustment with the trim-and-fill method. The pooled HR of 3 studies examining mutations at K-ras codon 13 was 1.47 (95% CI: 1.09-1.97, p = 0.02), and no publication bias was observed. No significant association was observed in different study regions.

LIMITATIONS

: The heterogeneity in the study populations is a potential problem, the use of different staging systems or small groups of different stages may contribute to heterogeneity, and residual confounding may have influenced the results in those studies that did not completely adjust for other factors.

CONCLUSIONS

: Overall K-ras gene mutations seem not to correlate with the prognosis of patients with colorectal cancer. The association remains to be confirmed with a more precise analysis of a large sample.

Predictive markers of colorectal cancer liver metastases

Liver metastases are the most common site of distant failure after curative resection of colorectal cancer and a source of significant cancer-related morbidity and mortality. Currently, imaging and conventional histopathologic features, such as T-stage and N-stage, are used by clinicians to inform prognosis and guide adjuvant treatment to reduce the risk of developing distant metastases. However, these tools only have a moderate ability to predict the development of liver metastases. Novel methods, including the detection of circulating tumor cells and carcinoembryonic antigens in serum, have been developed, and their prognostic and predictive characteristics have been assessed. In addition, several molecular and genetic markers in the primary tumor have been studied. Unfortunately, these studies are often small and their results have been mixed, yielding no consistent sets of externally validated predictors of colorectal liver metastases. For widespread clinical relevance, future tests need to be independently carried out on large independent patient samples.

Recent advances in detection of k-ras gene mutations and targeted therapy of colorectal cancer

Numerous studies have shown that anti-epidermal growth factor receptor (EGFR) monoclonal antibodies are effective in the treatment of colorectal cancer patients with the wild-type k-ras gene. The k-ras gene encodes a G-protein that functions downstream of EGFR signaling. Since k-ras mutations result in abnormal activation of the EGFR signaling pathway, anti-EGFR monoclonal antibody treatment is ineffective for patients with k-ras mutations. Therefore, k-ras mutation analysis is very important for targeted therapy of patients with colorectal cancer. This paper gives an overview of the recent advances in detection of k-ras gene mutations and targeted therapy of colorectal cancer.

A review of the most promising biomarkers in colorectal cancer: one step closer to targeted therapy

Rapidly growing insights into the molecular biology of colorectal cancer (CRC) and recent developments in gene sequencing and molecular diagnostics have led to high expectations for the identification of molecular markers to be used in optimized and tailored treatment regimens. However, many of the published data on molecular biomarkers are contradictory in their findings and the current reality is that no molecular marker, other than the KRAS gene in the case of epidermal growth factor receptor (EGFR)- targeted therapy for metastatic disease, has made it into clinical practice. Many markers investigated suffer from technical shortcomings, resulting from lack of quantitative techniques to capture the impact of the molecular alteration. This understanding has recently led to the more comprehensive approaches of global gene expression profiling or genome-wide analysis to determine prognostic and predictive signatures in tumors. In this review, an update of the most recent data on promising biological prognostic and/or predictive markers, including microsatellite instability, epidermal growth factor receptor, KRAS, BRAF, CpG island methylator phenotype, cytotoxic T lymphocytes, forkhead box P3-positive T cells, receptor for hyaluronic acid-mediated motility, phosphatase and tensin homolog, and T-cell originated protein kinase, in patients with CRC is provided.

Association of polymorphisms MTHFR C677T and A1298C with risk of colorectal cancer, genetic and epigenetic characteristic of tumors, and response to chemotherapy

BACKGROUND AND AIMS

The enzyme MTHFR plays an important role in folate metabolism, and folate is implicated in carcinogenesis due to its role in DNA methylation, repair, and synthesis. We analyze the relationship of MTHFR C677T and A1298C polymorphisms with biological, clinicopathological, genetic and epigenetic features of tumors, and the patient outcome after treatment with 5-FU-based chemotherapy to determine the contribution of MTHFR genotypes in the risk of colorectal cancer (CRC) and in the response to therapy.

METHODS

Genomic DNA of 143 Spanish sporadic CRC and 103 controls was analyzed by polymerase chain reaction/restriction fragment length polymorphism and sequencing.

RESULTS

The C677T polymorphism has protective effect on CRC showing TT genotype an odds ratios of 0.06 (95% confidence interval (CI): 0.10-0.32) and the CT of 0.51 (95% CI: 0.3-0.87). MTHFR A1298C polymorphism is not associated with CRC risk. Patients with 1298CC and AC genotypes exhibit worse survival than those with the wild genotype (log rank, p = 0.001), whereas C677T genotypes do not affect patient survival (log rank, p = 0.92). MTHFR 677T allele carriers responded better to 5-FU-based chemotherapy than patients with the wild CC genotype (log rank, p = 0.05). The variant C allele of A1298C affects negatively the response to 5-FU-based chemotherapy (log rank, p = 0.009).

CONCLUSIONS

The variant allele of the C677T has a protective effect on CRC development, whereas the variant allele of the A1298C does not produce any effect on disease risk. Both MTHFR polymorphisms are relevant and independent factors of patient outcome after 5FU-based treatment of CRC, and MTHFR genotyping may be of predictive benefit in selecting treatment regimens.

Prognostic role of KRAS and BRAF in stage II and III resected colon cancer: results of the translational study on the PETACC-3, EORTC 40993, SAKK 60-00 trial

PURPOSE

Mutations within the KRAS proto-oncogene have predictive value but are of uncertain prognostic value in the treatment of advanced colorectal cancer. We took advantage of PETACC-3, an adjuvant trial with 3,278 patients with stage II to III colon cancer, to evaluate the prognostic value of KRAS and BRAF tumor mutation status in this setting.

PATIENTS AND METHODS

Formalin-fixed paraffin-embedded tissue blocks (n = 1,564) were prospectively collected and DNA was extracted from tissue sections from 1,404 cases. Planned analysis of KRAS exon 2 and BRAF exon 15 mutations was performed by allele-specific real-time polymerase chain reaction. Survival analyses were based on univariate and multivariate proportional hazard regression models.

RESULTS

KRAS and BRAF tumor mutation rates were 37.0% and 7.9%, respectively, and were not significantly different according to tumor stage. In a multivariate analysis containing stage, tumor site, nodal status, sex, age, grade, and microsatellite instability (MSI) status, KRAS mutation was associated with grade (P = .0016), while BRAF mutation was significantly associated with female sex (P = .017), and highly significantly associated with right-sided tumors, older age, high grade, and MSI-high tumors (all P < 10(-4)). In univariate and multivariate analysis, KRAS mutations did not have a major prognostic value regarding relapse-free survival (RFS) or overall survival (OS). BRAF mutation was not prognostic for RFS, but was for OS, particularly in patients with MSI-low (MSI-L) and stable (MSI-S) tumors (hazard ratio, 2.2; 95% CI, 1.4 to 3.4; P = .0003).

CONCLUSION

In stage II-III colon cancer, the KRAS mutation status does not have major prognostic value. BRAF is prognostic for OS in MS-L/S tumors.

A MLH1 polymorphism that increases cancer risk is associated with better outcome in sporadic colorectal cancer

Germline mutations or the malfunctioning of postreplicative mismatch repair genes (MMR) are responsible of hereditary nonpolyposis colorectal cancer (HNPCC), and are also implied in some sporadic colorectal cancer (CRC) forms without any familial history of this disease. Besides germinal mutations and methylation, single-nucleotide polymorphisms (SNP) can predispose to nonfamilial CRC with low to moderate penetrance. In this case-control study, we analyzed three MLH1 single-nucleotide polymorphisms (exon 5: 415G-->C, rs28930073; exon 8: 655A-->G, rs1799977 and exon 16: 1852-1853AA-->GC) in 140 sporadic colorectal cancer cases and 125 healthy individuals to evaluate the relationship among CRC risk and clinicopathologic and genetic characteristics of the tumors. In our study, no 415G-->C variant carrier was found among all analyzed samples. The 1852-1853AA-->GC is a rare variant detected in heterozygoses in five controls and one case. In relation to the more frequent 655A-->G polymorphism, association analyses revealed that G carriers (AG or GG genotype) displayed a higher risk of CRC compared with AA homozygous [odds ratio (OR) AG=2.55, 95% confidence interval (CI)=1.48-4.39; P=0.01 and OR GG=2.48, 95% CI=1.20-5.11; P=0.01, respectively]. G-carrier males showed high CRC risk compared with homozygous AA wild-type individuals (OR: AG=3.05; 95% CI=1.49-6.26, P=0.002; OR: GG=3.60; 95% CI=1.29-10.03). Nevertheless, patients carrying the G allele displayed a better outcome than wild-type genotype carriers (log rank=7.26; P=0.007) and did not present vascular invasion (P=0.03), distant metastasis (P=0.004), or recurrence (P=0.01). MLH1 655A-->G change is associated with an increased risk, although it seems to have a favorable effect on patients, providing a better outcome. Moreover, our results suggest that for genomic profiling to predict the clinical outcome of patients with colorectal cancer, gender must also be considered.

Genetic and epigenetic changes in primary metastatic and nonmetastatic colorectal cancer

Colorectal cancer (CRC) develops as multistep process, which involves genetic and epigenetic alterations. K-Ras, p53 and B-Raf mutations and RASSF1A, E-Cadherin and p16INK4A promoter methylation were investigated in 202 CRCs with and without lymph node and/or liver metastasis, to assess whether gene abnormalities are related to a metastogenic phenotype. K-Ras, B-Raf and p53 mutations were detected in 27, 3 and 32% of the cases, with K-Ras mutations significantly associated with metastatic tumour (P=0.019). RASSF1A, E-Cadherin and p16INK4A methylation was documented in 20, 44 and 33% of the cases with p16INK4A significantly associated with metastatic tumours (P=0.001). Overall, out of 202 tumours, 34 (17%) did not show any molecular change, 125 (62%) had one or two and 43 (21%) three or more. Primary but yet metastatic CRCs were prevalent in the latter group (P=0.023) where the most frequent combination was one genetic (K-Ras in particular) and two epigenetic alterations. In conclusion, this analysis provided to detect some molecular differences between primary metastatic and nonmetastatic CRCs, with K-Ras and p16INK4A statistically altered in metastatic tumours; particular gene combinations, such as coincidental K-Ras mutation with two methylated genes are associated to a metastogenic phenotype.

Do MSI-L Sporadic Colorectal Tumors Develop Through “Mild Mutator Pathway”?

BACKGROUND

The mutator pathway implied in the development of colorectal cancer (CRC) is characterized by microsatellite instability (MSI). MSI tumors can be subdivided according to the level of instability: MSI-H (high), MSI-L (low) or stable MSS. MSI-H CRC displays a well described distinct phenotype, but the true biologic significance of MSI-L is still uncertain. The objective of this study was to further clarify if the MSI-L phenotype could reflect a distinct pathway of tumor development with a different clinical behavior.

METHODS

We analyzed the clinicopathological and genetic variables of 156 patients with sporadic CRC in relation with the level of MSI of the tumors.

RESULTS

We have found that MSI-L tumors are someway in the middle of MSI-H and MSS CRC, as they share some features with each of the other 2 subgroups: left side location, lower incidence of LOH at MSH2 as MSS and Dukes B (stage II TNM) like MSI-H. Moreover, MSI-L tumors show higher incidence of KRAS mutations.

CONCLUSION

We believe that MSI-L tumors could be considered a distinct phenotype that develops through a "mild mutator pathway."

RIS1, a gene with trinucleotide repeats, is a target in the mutator pathway of colorectal carcinogenesis

Microsatellite instability (MSI) due to mismatch repair system (MMR) alterations characterizes the mutator pathway implied in colorectal cancer development. In the present study, we have analyzed the gene RIS1 (Ras-induced senescence 1) in relation to loss of heterozygosity (LOH) and its frameshift mutations for an imperfect trinucleotide repeat (GCN) located at the 3'-OH end. Additionally, we have compared the status of RIS1 with a number of genetic and clinicopathological variables. RIS1 did not display LOH in any informative tumor of our series, but exhibited frameshift mutations in a high percentage (43.8%) of high-frequency MSI tumors (MSI-H), and its alteration was correlated with mutations in two target genes: BAX and TGFBR2. Moreover, mutations in RIS1 in MSI-H tumors correlated with the epigenetic silencing of MLH1 (P = 0.04). Finally, RIS1 seemed to be functionally involved in tumor development, as low-frequency MSI tumors (MSI-L) with RIS1 mutated usually were associated with a worse prognosis: 83% of them developed metastasis, and no patient with MSI-L tumor and RIS1 mutated (35.3% of MSI-L) survived >25 months after surgery (log rank P < 0.001). All these results indicate, according to the Bethesda criteria, that RIS1 is a target gene in the mutator pathway.

Prognostic significance of bcl-2 and p53 expression in colorectal carcinoma

OBJECTIVE

This study was designed to detect the expression of bcl-2 and p53 proteins in colorectal carcinomas and to determine their association with the patient survival and stage of the diseases.

METHODS

Immunohistochemistry method was used to detect the expression of bcl-2 and p53 proteins in 93 cases of colorectal carcinoma. The stain results were obtained by analyzing the clinic-pathological characteristics of patients.

RESULTS

Fifty-seven percent (53/93) of the colorectal carcinomas were bcl-2 protein positive. The positive rate of bcl-2 protein in lymph node involvement cases was lower (15/37) than the cases without node involvement (38/58, P<0.01). The positive rate of p53 protein was 43% (40/93) in colon-rectum carcinomas. No significant correlation was observed between p53 protein expression and clinic-pathological manifestations (P>0.05) but the survival was significantly worse (P=0.0001) in the p53 protein positive cases. Neither bcl-2 nor p53 alone was correlated with stage of the disease. When combined bcl-2/p53 status was analyzed, a group with bcl-2(+) and p53(-) had the best prognosis. This group was significantly associated with earlier Dukes' stages (P=0.1763). In multivariate Cox regression analysis, lymph node involvement and p53 protein expression were two independent factors correlated with survival time.

CONCLUSION

The expression of bcl-2 and p53 represent biological characteristics of colorectal carcinomas. Assessment of both bcl-2 and p53 status may be valuable in predicting the prognosis of patients.

Mutant KRAS, chromosomal instability and prognosis in colorectal cancer

The RAS gene family provides a global effect on gene expression by encoding small GTP-binding proteins which act as molecular switches connecting extracellular signals with nuclear transcription factors. While wild type RAS proteins are switched off shortly after activation, mutant RAS proteins remain constitutively activated leading to complex interactions among their downstream effectors. For some human tumor types, these interactions were shown to contribute to cancer genesis and progression by inducing changes in cell survival, apoptosis, angiogenesis, invasion and metastasis. This review addresses the controversial link of KRAS mutations in colorectal cancer with chromosomal instability and patient prognosis.

Significance of mutations in TGFBR2 and BAX in neoplastic progression and patient outcome in sporadic colorectal tumors with high-frequency microsatellite instability

The mutator pathway implied in the development of colorectal cancer is characterized by microsatellite instability (MSI), which is determined by alterations of mismatch repair (MMR) genes. Defects in MMR genes affect repetitive DNA tracts interspersed mostly between coding sequences, and therefore it cannot be expected that they play a role during tumor progression. Genes containing repetitive sequences within their coding regions could be targets for MSI tumorigenesis, but this does not necessarily imply a causal role for the affected gene, because most are probably passenger mutations. We analyzed MSI and TGFBR2 and BAX frameshift mutations to further clarify the relationships between inactivation of the two genes and genomic instability in sporadic colorectal cancer (CRC), and to address how mutations in these genes influence the development of tumors and, eventually, patient outcome. One hundred and fifty-five patients with sporadic CRC were classified according to their MSI status. Frameshift mutations in the two genes were recurrent in high-frequency MSI (MSI-H) tumors, but these tended to be more common in poorly differentiated tumors. A high rate of mutations of TGFBR2 was found in tumors at Dukes' B stage, showing a greater extent of vascular invasion. Finally, in MSI-H tumors, mutations of either gene were associated with a significant decrease in survival. Our results contribute to the understanding of how the TGFBR2 and BAX gene mutations contribute to tumor progression in the mutator phenotype pathway for MSI colorectal cancers.