Prognostic significance of K-ras and TP53 mutations in the role of adjuvant chemotherapy on survival in patients with Dukes C colon cancer

Prognostic value of 5-microRNA based signature in T2-T3N0 colon cancer

The role of adjuvant chemotherapy in stage T2-T3N0 colon cancer (CC) is controversial and there are currently no reliable factors allowing for individual selection of patients with high risk of relapse for such therapy. We searched for microRNA-based signature with prognostic significance in this group. We assessed by qRT-PCR expression of 754 microRNAs (miRNAs) in tumour samples from 85 stage pT2-3N0 CC patients treated with surgery alone. MiRNA expression was compared between two groups of patients: 40 and 45 patients who did and did not develop distant metastases after resection, respectively. Additionally, miRNA expression was compared between CC and normal colon mucosa samples and between the mismatch repair (MMR) competent and deficient tumours. Low expression of miR-1300 and miR-939 was significantly correlated with shorter distant metastasis-free survival (DMFS) in Cox univariate analysis (p.adjusted = 0.049). The expression signature of five miRNAs (miR-1296, miR-135b, miR-539, miR-572 and miR-185) was found to be prognostic [p = 1.28E−07, HR 8.4 (95 % CI: 3.81–18.52)] for DMFS and cross-validated in a leave-one-out analysis, with the sensitivity and specificity of 74 and 78 %, respectively. The expression of miR-592 was significantly associated with the MMR status (p.adjusted <0.01). The expression of several novel miRNAs were found to be tumour specific, e.g. miR-888, miR-523, miR-18b, miR-302a, miR-423-5p, miR-582-3p (p < 0.05). We developed a miRNA expression signature that may be predictive for the risk of distant relapse in early stage CC and confirmed previously reported association between miR-592 expression and MMR status.

TP53 Mutational Status and Prediction of Benefit from Adjuvant 5-Fluorouracil in Stage III Colon Cancer Patients

We investigated the hypothesis that the varying treatment efficacy of adjuvant 5-fluorouracil (5FU) in stage III colon cancer is linked to the TP53 mutational status.

ABCSG-90 was a prospective randomized trial in which effect of adjuvant 5FU was studied in stage III colon cancer patients. Tumor material of 70% of these patients (389/572) was available for analysis of the biomarker TP53 using a TP53-gene-specific Sanger sequencing protocol.

Median follow-up was 88 months. TP53 mutation frequency was 33%. A significant interaction between TP53 status, outcomes and nodal category was found (P = 0.0095). In the N1 category, TP53 wildtype patients had significantly better overall survival than TP53 mutated (81.0% vs. 62.0% overall survival at 5 years; HR = 2.131; 95% CI: 1.344–3.378; P = 0.0010). In the N2 category, the TP53 status did not affect survival (P = 0.4992). In TP53 wildtype patients, the prognostic significance of N category was significantly enhanced (P = 0.0002). In TP53 mutated patients, survival curves of N1 and N2 patients overlapped and nodal category was no longer prognostic.

The biomarker TP53 independently predicted effect of adjuvant 5FU in N1 colon cancer patients. TP53 was not predictive in N2 patients, in whom 5FU is known to have no effect.

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The TP53 status was found to be an independent predictive marker for the effect of adjuvant 5FU in stage III colon cancer.

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In the N1 category, patients with wildtype TP53 experienced a significant survival benefit from adjuvant 5FU.

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In TP53 mutant patients survival curves of N1 and N2 patients overlapped and nodal category was no longer prognostic.

Postoperative chemotherapy is recommended for all patients with lymph node positive colon cancer. In colon cancer, mutations in the TP53 gene are present in more than 30% of tumors. We found that the most commonly used postoperative chemotherapy resulted in a marked survival benefit for patients with normal TP53 status while it was associated with significant survival disadvantage in TP53 mutant patients. Overall the survival disadvantage of the mutated patients almost balanced the survival benefit of the TP53 normal patients. This might be an explanation why chemotherapy resulted in less progress in survival of colon cancer than we would have expected.

Determinants of recurrence after intended curative resection for colorectal cancer

Despite intended curative resection, colorectal cancer will recur in ∼45% of the patients. Results of meta-analyses conclude that frequent follow-up does not lead to early detection of recurrence, but improves overall survival. The present literature shows that several factors play important roles in development of recurrence. It is well established that emergency surgery is a major determinant of recurrence. Moreover, anastomotic leakages, postoperative bacterial infections, and blood transfusions increase the recurrence rates although the exact mechanisms still remain obscure. From pathology studies it has been shown that tumors behave differently depending on their location and recur more often when micrometastases are present in lymph nodes and around vessels and nerves. K-ras mutations, microsatellite instability, and mismatch repair genes have also been shown to be important in relation with recurrences, and tumors appear to have different mutations depending on their location. Patients with stage II or III disease are often treated with adjuvant chemotherapy despite the fact that the treatments are far from efficient among all patients, who are at risk of recurrence. Studies are now being presented identifying subgroups, in which the therapy is inefficient. Unfortunately, only few of these facts are implemented in the present follow-up programs. Therefore, further research is urgently needed to verify which of the well-known parameters as well as new parameters that must be added to the current follow-up programs to identify patients at risk of recurrence.

Can K-ras gene mutation be utilized as prognostic biomarker for colorectal cancer patients receiving chemotherapy? A meta-analysis and systematic review

INTRODUCTION

K-ras gene mutations were common in colorectal patients, but their relationship with prognosis was unclear.

OBJECTIVE

Verify prognostic differences between patient with and without mutant K-ras genes by reviewing the published evidence.

METHOD

Systematic reviews and data bases were searched for cohort/case-control studies of prognosis of colorectal cancer patients with detected K-ras mutations versus those without mutant K-ras genes, both of whom received chemotherapy. Number of patients, regimens of chemotherapy, and short-term or long-term survival rate (disease-free or overall) were extracted. Quality of studies was also evaluated.

PRINCIPAL FINDINGS

7 studies of comparisons with a control group were identified. No association between K-ras gene status with neither short-term disease free-survival (OR=1.01, 95% CI, 0.73-1.38, P=0.97) nor overall survival (OR=1.06, 95% CI, 0.82-1.36, P=0.66) in CRC patients who received chemotherapy was indicated. Comparison of long-term survival between two groups also indicated no significant difference after heterogeneity was eliminated (OR=1.09, 95% CI, 0.85-1.40, P=0.49).

CONCLUSIONS

K-ras gene mutations may not be a prognostic index for colorectal cancer patients who received chemotherapy.

Clinical impact of K-ras mutation in colorectal cancer patients treated with adjuvant FOLFOX

BACKGROUND

K-ras proto-oncogene is commonly mutated in colorectal cancer (CRC) and has been associated with predictive markers for anti-EGFR (epidermal growth factor receptor) therapy. However, the prognostic role of K-ras status is still unclear. The aim of this study was to evaluate the association between k-ras status and addition of oxaliplatin to fluorouracil plus leucovorin (FOLFOX) chemotherapy in CRC patients with curative surgical resection.

METHODS

Sixty-six patients with stage II or III CRC were treated with FOLFOX or fluorouracil plus leucovorin (FL) followed by curative surgery between January 2004 and October 2007. K-ras status was assessed by direct sequencing.

RESULTS

Fifteen patients (22.7%) had K-ras mutations of codon 12 (11/15) or codon 13 (4/15). There were no significant differences in clinicopathological parameters, such as age, sex, stage, or adjuvant regimen between the wild-type K-ras and mutant K-ras. With a median follow-up of 41.6 months (range 25.1-72.3 months), median disease-free survival (DFS) and overall survival (OS) were not reached. With regard to K-ras status, DFS and OS were not statistically different (P = 0.269 and P = 0.917, respectively). Even in the group treated with FOLFOX only, neither DFS (P = 0.651) nor OS (P = 0.265) was significantly different according to K-ras status. With the exception of tumor location in DFS and OS, no differences in other variables were observed. Proximal colon cancer patients had a longer DFS than distal CRC patients (P = 0.079); this trend was maintained only in the wild-type K-ras group (P = 0.051).

CONCLUSIONS

These results showed that K-ras status was not associated with clinical outcome in patients treated with adjuvant FOLFOX.

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.

Analysis of molecular alterations in left- and right-sided colorectal carcinomas reveals distinct pathways of carcinogenesis: proposal for new molecular profile of colorectal carcinomas

To clarify distinct genetic profiles of colorectal cancers based on tumor location (left- and right-sided), we evaluated the status of loss of heterozygosity (LOH), CpG islands methylation phenotype (CIMP), microsatellite instability (MSI), and mutations of p53, Ki-ras, and APC genes in 119 colorectal cancers. Statuses of LOH (at 5q, 8p, 17p, 18q, and 22q), MSI, and CIMP (MINT1, MINT2, MINT31, MLH-1, MGMT, p14, p16, and RASSF1A) were determined using microsatellite polymerase chain reaction and methylation-specific polymerase chain reaction coupled with a crypt isolation method, respectively. In addition, mutations of p53, Ki-ras, and APC genes were also examined. LOH, MSI, and CIMP status allowed us to classify samples into two groups: low or negative and high or positive. Whereas the frequency of p53 mutations in the LOH-high status was significantly higher in left-sided cancers than in right-sided cancers, CIMP-high in the LOH-high status and MSI-positive status were more frequently found in right-sided cancers compared with left-sided cancers. Finally, location-specific methylated loci were seen in colorectal cancers: type I (dominant in right-sided cancer) and type II (common in both segments of cancer). Our data confirm that distinct molecular pathways to colorectal cancer dominate in the left and right sides of the bowel.

Peroxisome proliferator-activated receptor gamma and spermidine/spermine N1-acetyltransferase gene expressions are significantly correlated in human colorectal cancer

Background

The peroxisome proliferator-activated receptor γ (PPARγ) is a transcription factor that regulates adipogenic differentiation and glucose homeostasis. Spermidine/spermine N¹-acetyltransferase (SSAT) and ornithine decarboxylase (ODC) are key enzymes involved in the metabolism of polyamines, compounds that play an important role in cell proliferation. While the PPARγ role in tumour growth has not been clearly defined, the involvement of the altered polyamine metabolism in colorectal carcinogenesis has been established. In this direction, we have evaluated the PPARγ expression and its relationship with polyamine metabolism in tissue samples from 40 patients operated because of colorectal carcinoma. Since it is known that the functional role of K-ras mutation in colorectal tumorigenesis is associated with cell growth and differentiation, polyamine metabolism and the PPARγ expression were also investigated in terms of K-ras mutation.

Methods

PPARγ, ODC and SSAT mRNA levels were evaluated by reverse transcriptase and real-time PCR. Polyamines were quantified by high performance liquid chromatography (HPLC). ODC and SSAT activity were measured by a radiometric technique.

Results

PPARγ expression, as well as SSAT and ODC mRNA levels were significantly higher in cancer as compared to normal mucosa. Tumour samples also showed significantly higher polyamine levels and ODC and SSAT activities in comparison to normal samples. A significant and positive correlation between PPARγ and the SSAT gene expression was observed in both normal and neoplastic tissue (r = 0.73, p < 0.0001; r = 0.65, p < 0.0001, respectively). Moreover, gene expression, polyamine levels and enzymatic activities were increased in colorectal carcinoma samples expressing K-ras mutation as compared to non mutated K-ras samples.

Conclusion

In conclusion, our data demonstrated a close relationship between PPARγ and SSAT in human colorectal cancer and this could represent an attempt to decrease polyamine levels and to reduce cell growth and tumour development. Therefore, pharmacological activation of PPARγ and/or induction of SSAT may represent a therapeutic or preventive strategy for treating colorectal cancer.

Links between Biology, Prognosis and Prediction of Response to Chemotherapy in Colorectal Cancer

Compared with the progress achieved in breast cancer, the use of prognostic and predictive parameters in colorectal cancer is lagging behind. One of the reasons is the limited information provided by 'classic' mutations as markers for response to therapy. To bridge this gap, prospective clinical trials need to be conducted to evaluate the usefulness of gene expression profiling and candidate markers, such as DNA repair proteins, onset of the methylator phenotype, neo-angiogenetic pathways related to inflammation, matrix metalloproteinases, tumor suppressors and cell signaling pathways (e.g. Akt). In parallel, the unrivalled sensitivity of molecular techniques may be applied to diagnostic parameters, such as cytokeratin 20 mRNA, for the detection of lymph node metastases. This article reviews the current knowledge on prognostic and predictive parameters in order to highlight the close link between tumor biology and tumor pharmacology. The increasing number of candidate markers together with recently introduced therapeutic options offer novel opportunities for a stepwise approach to the ambitious goal of individualized therapy in colorectal cancer.

p53 is an independent pre-treatment markers for long-term survival in stage II and III colorectal cancers: an analysis of interaction between genetic markers and fluorouracil-based adjuvant therapy

One hundred and thirty-eight stage II and III colorectal cancer patients were included to evaluate the prognostic significance of genetic markers (including mutations of the p53, K-ras genes, and microsatellite instability) on the response to 5-fluorouracil (FU)-based post-operative adjuvant therapies (PAT). When stratified by PAT and adjusting for other prognostic variables, presence of p53 mutation was associated with a poor outcome (hazard ratio (HR)=3.1, 95% confidence interval (CI), 0.9-11.0) among patients without PAT. Our data confirmed that p53 mutation is an independent pre-treatment factor in stage II and III colorectal cancer after curative resection.

Anticancer drug response and expression of molecular markers in early-passage xenotransplanted colon carcinomas

Despite some success in the treatment of colorectal carcinomas, novel rational therapies targeting specific cancer-related molecules are under development and urgently needed. These approaches need careful preclinical evaluation in models that closely mirror the clinical situation. Therefore, we established a panel of 15 xenotransplantable tumours directly from fresh surgical material. We showed that both the histology and expression of tumour-associated markers (Epithelial Cell Adhesion molecule (EpCAM), E-cadherin, carcinoembryonic antigen (CEA)) could be maintained during passaging in nude mice. Xenotransplanted tumours were characterised for chemosensitivity and revealed a response rate of 5/15 (33%) for 5-fluorouracil (5-FU), 15/15 (100%) for irinotecan and 8/14 (57%) for oxaliplatin. 5 patients out of 15 were treated with cytostatics because of synchronous metastases. The response to chemotherapy in these patients coincided very closely with the response of the individual xenografts. All of the xenografts expressed the proliferation marker Ki67 and the nuclear enzyme, Topoisomerase IIalpha (Topo IIalpha) at the protein level. Most of the xenografts also expressed the tumour suppressor, p53 (9/14) and the nuclear enzyme Topoisomerase Ialpha (Topo Ialpha) (13/14) at the protein level. Interestingly, the presence of a K-ras mutation in codon 12 (5/15 xenografts) coincided with a low response rate towards oxaliplatin. This observation needs further confirmation using a larger number of tumours. In conclusion, we were able to establish transplantable xenografts suitable to mimic the clinical situation. These well characterised models are useful tools for the preclinical development of novel therapeutic approaches and for investigating translational research aspects.

Molecular lesions in colorectal cancer: impact on prognosis? Original data and review of the literature

BACKGROUND

In the Dukes' B and C stages of colorectal carcinoma there are considerable variations in the observed courses of the disease. Since post-operative chemotherapy in patients with Dukes' C (node-positive) colon carcinoma has been demonstrated to be effective in improving overall-survival, a more exact prognosis assessment gains additional significance and therapeutic relevance.

DISCUSSION

One also hopes to derive improved prognostic factors from the clarification of the molecular pathogenesis. Because of its frequency and the accessibility and recognizability of its developmental stages colorectal carcinoma is among the best investigated of all solid tumors. Despite a multitude of suggested molecular candidate markers none of these changes has yet been able enter the everyday life of the clinic. However, it is to be expected that some of the molecular alterations presently discussed will gain importance before long in the clinical treatment of patients with colorectal carcinoma.

CONCLUSION

Considering also our own findings, this review presents the latest developments in the scientific discussion of the tumor suppressor/oncogenes p53, k-ras, and DCC, biochemical determinants of the 5-fluorouracil metabolism, and defects of the DNA repair system.

Adverse histopathological findings as a guide to patient management after curative resection of node-positive colonic cancer

Background

The aim of this study was to identify patient and tumour characteristics that might assist in developing an improved approach to patient selection for chemotherapy after resection of clinicopathological stage C colonic cancer.

Methods

Clinical, pathological and follow-up data have been collected prospectively for all patients undergoing resection for colorectal cancer at Concord Hospital since 1971. From an initial 2980 patients, after exclusions 378 remained who had a potentially curative operation for colonic cancer with nodal metastases and did not receive adjuvant chemotherapy. Associations between several pathological features and survival were examined by proportional hazards regression.

Results

In a multivariate model, both overall and colonic cancer-specific survival rates were negatively associated with serosal surface involvement, apical node metastasis, high histological grade and venous invasion. The survival of patients with stage C disease who had none of these adverse features was not significantly different from that of patients with stage B lesions. However, survival diminished significantly when one or more of the adverse features were present.

Conclusion

Patients with a stage C tumour but with none of the identified adverse features experience relatively good survival and are unlikely to benefit from adjuvant chemotherapy. In this series such patients accounted for 40·5 per cent of patients with stage C disease.

P53 overexpression predicts poor chemosensitivity to high-dose 5-fluorouracil plus leucovorin chemotherapy for stage IV colorectal cancers after palliative bowel resection

Our study aims to further clarify the prognostic significance of p53 overexpression in stage IV colorectal cancer. Between January 1994 and June 1997, we recruited 144 patients with stage IV colorectal cancers for our study, based on appropriate eligibility criteria. The patients were nonrandomly allocated to 2 treatment groups of either with or without high-dose 5-fluorouracil plus leucovorin chemotherapy (HDFL: 5-Fu: 2,600 mg/m(2) leucovorin 300 mg/m maximum 500 mg). Each treatment group was further divided into 2 subgroups according to the status of p53 overexpression. Therefore, 4 subgroups were allocated in our study and were designated as p53 (overexpression) HDFL (+), n = 65; p53 (normal) HDFL (+), n = 37; p53 (overexpression) HDFL (-), n = 27; and p53 (normal) HDFL (-), n = 15, respectively. All patients were prospectively followed until April 2001. There was no significant difference of the background clinicopathologic data of these 4 allocated subgroups of patients (p > 0.05). Multivariate analysis of various clinicopathologic factors of the whole group of patients indicated that age > or = 60 years, poor differentiation, mucin production, CEA > 100 ng/ml, p53 overexpression and without chemotherapy were the significant independent poor prognostic factors (p < 0.05). Survival analyses indicated that the patients of subgroup p53 (normal) HDFL (+) survived significantly longer than those of subgroup p53 (overexpression) HDFL (+), with mean survival time (95% confidence interval [CI]) of 20.24 (16.24-24.25) and 13.29 (10.98-15.60) months, respectively (p = 0.0043, log-rank test). In contrast, in patients without chemotherapy, the prognosis was poor regardless of their p53 status, with mean survival time (95% CI) of 6.85 (5.47-8.23) and 5.87 (4.48-7.26) months in p53 (overexpression) HDFL (-) and p53 (normal) HDFL (-) subgroups of patients, respectively (p = 0.2820, log-rank test). Cancers of normal p53 expression responded significantly better to HDFL (p < 0.05), with mean response rate (95% CI) being 65.57% (52.18-82.96%) in subgroup p53 (normal) HDFL (+) as compared to 35.38% (23.52-47.24%) in subgroup p53 (overexpression) HDFL (+). The toxicity to HDFL was similarly minimal between p53-normal and p53-overexpression patients (p > 0.05). We thus concluded that the poorer prognosis of stage IV colorectal cancers with p53 overexpression was associated with their poorer chemosensitivity rather than the more biologic aggressiveness.