Prognostic significance of TP53 gene mutation in 995 cases of colorectal carcinoma. Influence of tumour site, stage, adjuvant chemotherapy and type of mutation

Association of β-Catenin, APC, SMAD3/4, Tp53, and Cyclin D1 Genes in Colorectal Cancer: A Systematic Review and Meta-Analysis

Objectives

Accumulating evidence indicates that the expression and/or variants of several genes play an essential role in the progress of colorectal cancer (CRC). The current study is a meta-analysis undertaken to estimate the prognosis and survival associated with CTNNB1/β-catenin, APC, Wnt, SMAD3/4, TP53, and Cyclin D1 genes among CRC patients.

Methods

The authors searched PubMed, EMBASE, and Science Direct for relevant reports published between 2000 and 2020 and analyzed them to determine any relationship between the (immunohistochemically/sequencing-detected) gene expression and variants of the selected genes and the survival of CRC patients.

Results

The analysis included 34,074 patients from 64 studies. To evaluate association, hazard ratios (HRs) were estimated for overall survival (OS) or disease-free survival (DFS), with a 95% confidence interval (CIs). Pooled results showed that β-catenin overexpression, APC mutation, SMAD-3 or 4 loss of expression, TP53 mutations, and Cyclin D1 expression were associated with shorter OS. β-Catenin overexpression (HR: 0.137 (95% CI: 0.131–0.406)), loss of expression of SMAD3 or 4 (HR: 0.449 (95% CI: 0.146–0.753)), the mutations of TP53 (HR: 0.179 (95% CI: 0.126–0.485)), and Cyclin D1 expression (HR: 0.485 (95% CI: 0.772–0.198)) also presented risk for shorter DFS.

Conclusions

The present meta-analysis indicates that overexpression or underexpression and variants of CTNNB1/β-catenin, APC, SMAD3/4, TP53, and Cyclin D1 genes potentially acted as unfavorable biomarkers for the prognosis of CRC. The Wnt gene was not associated with prognosis.

Isotypic analysis of anti-p53 serum autoantibodies and p53 protein tissue phenotypes in colorectal cancer

The presence of IgA- and IgM-specific autoantibody (AAb) isotypes and their relationship to p53 tissue expression patterns are not well understood. This study aims to investigate the clinical utility of the anti-p53 AAb isotypes and tissue positivity in colorectal cancer (CRC). We analysed anti-p53 IgG, IgM, and IgA AAbs in sera of 99 CRC patients and 99 non-cancer control subjects. Corresponding tissue expression of the p53 protein was evaluated by immunohistochemistry (IHC). Anti-p53 AAbs of the IgG isotype were present in the sera of 21 out of 99 patients (21%), while IgM AAbs were observed in 9 (9%) and IgA in 2 (2%) CRC patients. Anti-p53 AAbs of all three isotypes were generally associated with IHC staining indicative of mutated TP53. Seropositive anti-p53 IgM cases in the absence of anti-p53 IgG were linked to wild-type p53. Anti-p53 IgA in the absence of IgG AAbs was detected in two non-cancer controls indicating a potential p53 epitope mimicry. Although seropositivity was not associated with patient survival (P = 0.650), mutant-pattern p53 tissue expression was associated with reduced 5-year overall survival (P = 0.032), however, it was not an independent prognostic marker (Multivariate Cox regression, P = 0.193). In conclusion, immunoglobulin isotyping revealed that anti-p53 IgM and IgA AAbs were predominantly concurrent with anti-p53 serum IgG and the mutant-pattern p53 tissue phenotype. IgM and IgA seropositive cases in absence of anti-p53 IgG were linked to wild-type p53 tissue phenotype indicating early anti-p53 immune responses preceding isotype class-switch (IgM) or p53 antigen mimicry (IgA).

TP53 Copy Number and Protein Expression Inform Mutation Status across Risk Categories in Acute Myeloid Leukemia

Mutant TP53 is an adverse risk factor in acute myeloid leukemia (AML), but large-scale integrated genomic-proteomic analyses of p53 alterations in AML patients remain limited. We analyzed TP53 mutational status, copy number (CN), and protein expression data in AML (N=528) and provide a compilation of mutation sites and types across disease subgroups among treated and untreated patients. Our analysis shows differential hotspots in subsets of AML and uncovered novel pathogenic variants involving TP53 splice sites. In addition, we identified TP53 CN loss in 70.2% of TP53-mutated AML, which had more deleterious TP53 mutations and copy neutral loss of heterozygosity in 5/32 (15.6%) AML patients who had intact TP53 CN. Importantly, we demonstrate that mutant p53 protein expression patterns by immunohistochemistry evaluated using digital image-assisted analysis provide a robust readout that integrates TP53 mutation and allelic states in patients with AML (sensitivity=94.49%, specificity=90.48%). Protein expression of p53 by immunohistochemistry informed mutation status irrespective of TP53 CN status. Genomic analysis of co-mutations in TP53-mutant AML showed a muted landscape that encompassed primarily mutations in genes involved in epigenetic regulation (DNMT3A and TET2), RAS/MAPK signaling (NF1, KRAS/NRAS, PTPN11), and RNA splicing (SRSF2). In summary, our data provides a rationale to refine risk stratification of AML patients on the basis of integrated molecular and protein-level TP53 analyses.

Association of colorectal cancer with genetic and epigenetic variation in PEAR1—A population-based cohort study

Platelet Endothelial Aggregation Receptor 1 (PEAR1) modulates angiogenesis and platelet contact-induced activation, which play a role in the pathogenesis of colorectal cancer. We therefore tested the association of incident colorectal cancer and genetic and epigenetic variability in PEAR1 among 2532 randomly recruited participants enrolled in the family-based Flemish Study on Environment, Genes and Health Outcomes (51.2% women; mean age 44.8 years). All underwent genotyping of rs12566888 located in intron 1 of the PEAR1 gene; in 926 participants, methylation at 16 CpG sites in the PEAR1 promoter was also assessed. Over 18.1 years (median), 49 colorectal cancers occurred, all in different pedigrees. While accounting for clustering of risk factors within families and adjusting for sex, age, body mass index, the total-to-HDL cholesterol ratio, serum creatinine, plasma glucose, smoking and drinking, use of antiplatelet and nonsteroidal anti-inflammatory drug, the hazard ratio of colorectal cancer contrasting minor-allele (T) carriers vs. major-allele (GG) homozygotes was 2.17 (95% confidence interval, 1.18–3.99; P = 0.013). Bootstrapped analyses, from which we randomly excluded from two to nine cancer cases, provided confirmatory results. In participants with methylation data, we applied partial least square discriminant analysis (PLS-DA) and identified two methylation sites associated with higher colorectal cancer risk and two with lower risk. In-silico analysis suggested that methylation of the PEAR1 promoter at these four sites might affect binding of transcription factors p53, PAX5, and E2F-1, thereby modulating gene expression. In conclusion, our findings suggest that genetic and epigenetic variation in PEAR1 modulates the risk of colorectal cancer in white Flemish. To what extent, environmental factors as exemplified by our methylation data, interact with genetic predisposition and modulate penetrance of colorectal cancer risk is unknown.

Synchronous metastatic colon cancer and the importance of primary tumor laterality - A National Cancer Database analysis of right- versus left-sided colon cancer

BACKGROUND

The role of laterality for patients with synchronous metastatic colon cancer (SMCC) is not well-defined.

METHODS

Using the National Cancer Database (2010-2015), we compared patients with metastatic right- (RCC) versus left-sided colon cancer (LCC). We performed Kaplan-Meier analysis to compare overall survival (OS) for each metastatic site and utilized adjusted Cox proportional hazard analysis to identify predictors of OS.

RESULTS

Patients with RCCs were more likely to be older, female, and have more comorbidities. LCCs were more likely to metastasize to liver and lung, whereas RCCs were more likely to metastasize to peritoneum and brain. There was equal likelihood to metastasize to bone. OS was significantly longer for LCCs for all metastatic sites. After controlling for multiple variables, RCC (HR 1.426, p < 0.001) remained an independent predictor of worse OS compared to LCC.

CONCLUSIONS

Laterality of the primary tumor plays an important role in outcomes for patients with SMCC.

Overexpression of TP53 protein is associated with the lack of adjuvant chemotherapy benefit in patients with stage III colorectal cancer

TP53 mutations drive colorectal cancer development, with missense mutations frequently leading to accumulation of abnormal TP53 protein. TP53 alterations have been associated with poor prognosis and chemotherapy resistance, but data remain controversial. Here, we examined the predictive utility of TP53 overexpression in the context of current adjuvant treatment practice for patients with stage III colorectal cancer. A prospective cohort of 264 stage III patients was tested for association of TP53 expression with 5-year disease-free survival, grouped by adjuvant treatment. Findings were validated in an independent retrospective cohort of 274 stage III patients. Overexpression of TP53 protein (TP53+) was found in 53% and 52% of cases from the prospective and retrospective cohorts, respectively. Among patients receiving adjuvant chemotherapy, TP53+ status was associated with shorter disease-free survival (p ≤ 0.026 for both cohorts), while no difference in outcomes between TP53+ and TP53- cases was observed for patients treated with surgery alone. Considering patients with TP53- tumors, those receiving adjuvant treatment had better outcomes compared with those treated with surgery alone (p ≤ 0.018 for both cohorts), while no treatment benefit was apparent for patients with TP53+ tumors. Combined cohort-stratified analysis adjusted for clinicopathological variables and DNA mismatch repair status confirmed a significant interaction between TP53 expression and adjuvant treatment for disease-free survival (p_interaction = 0.030). For the combined cohort, the multivariate hazard ratio for TP53 overexpression among patients receiving adjuvant chemotherapy was 2.03 (95% confidence interval 1.41-2.95, p < 0.001), while the hazard ratio for adjuvant treatment among patients with TP53- tumors was 0.42 (95% confidence interval 0.24-0.71, p = 0.001). Findings were maintained irrespective of tumor location or when restricted to mismatch repair-proficient tumors. Our data suggest that adjuvant chemotherapy benefit in stage III colorectal cancer is restricted to cases with low-level TP53 protein expression. Identifying TP53+ tumors could highlight patients that may benefit from more aggressive treatment or follow-up.

The expression of the P2Y6 receptor is regulated at the transcriptional level by p53

Inflammatory bowel disease (IBD) is a risk factor for the development of colorectal cancer (CRC) for which mutation to p53 is an early event leading to dysplasia. Interestingly, P2RY6 mRNA increases in both pathologies. In this study, we investigated if p53 and p53^R273H mutant, commonly found in CRC and IBD, were involved in the transcriptional regulation of P2RY6. First, the P2RY6 promoter was defined as a region corresponding to -1600 to +273 nucleotides relative to the putative TATA-less transcriptional starting site found at position 73,264,505 of NCBI reference sequence NC_000010.11. We cloned this promoter region along with 5'-deletion constructs in the pGL4.10[luc2] vector for luciferase assays to delineate the minimal promoter region. We observed that p53 ^wt and p53^R273H differentially regulated the transcription of the P2RY6 gene. In fact, increasing quantity of p53^R273H enhanced the capacity of p53 ^wt to stimulate the transactivation of the P2RY6 promoter but this cooperative effect was lost when p53^R273H was present in a ratio of 3:1. In accordance with the luciferase assays, ChIP analysis revealed that endogenous p53 ^wt was significantly associated with the P2RY6 proximal promoter, whereas the interaction of the p53^R273H with the P2RY6 promoter was not significant. Although further studies are required to fully elucidate the molecular determinant controlling P2Y₆ expression in diseases, we propose, for the first time, a molecular mechanism involving a collaboration between p53 ^wt and p53^R273H to regulate the expression of this receptor.

CD44v6 engages in colorectal cancer progression

CD44 is a transmembrane glycoprotein. When the CD44 gene is expressed, its pre-messenger RNA (mRNA) can be alternatively spliced into mature mRNAs that encode several CD44 isoforms. The mRNA assembles with ten standard exons, and the sixth variant exon encodes CD44v6, which engages in a variety of biological processes, including cell growth, apoptosis, migration, and angiogenesis. Mechanistically, CD44v6 interacts with hyaluronic acid (HA) or osteopontin, or it acts as a coreceptor for various cytokines, such as epidermal growth factor, vascular endothelial growth factor, hepatocyte growth factor, and C-X-C motif chemokine 12. In this context, the receptor tyrosine kinase or G protein-coupled receptor-associated signaling pathways, including mitogen-activated protein kinase/extracellular-signal-regulated kinase and phosphoinositide-3-kinase/Akt, are activated. Using these actions, homeostasis or regeneration can be facilitated among normal tissues. However, overexpression of the mature mRNA encoding CD44v6 can induce cancer progression. For example, CD44v6 assists colorectal cancer stem cells in colonization, invasion, and metastasis. Overexpression of CD44v6 predicts poor prognosis in patients with colorectal cancer, as patients with a large number of CD44v6-positive cells in their tumors are generally diagnosed at late stages. Thus, the clinical significance of CD44v6 in colorectal cancer deserves consideration. Preclinical results have indicated satisfactory efficacies of anti-CD44 therapy among several cancers, including prostate cancer, pancreatic cancer, and gastric cancer. Moreover, clinical trials aiming to evaluate the pharmacokinetics, pharmacodynamics, efficacy, and toxicity of a commercialized anti-CD44 monoclonal antibody developed by Roche (RO5429083) have been conducted among patients with CD44-expressing malignant tumors, and a clinical trial focusing on the dose escalation of this antibody is ongoing. Thus, we are hopeful that anti-CD44 therapy will be applied in the treatment of colorectal cancer in the future.

The location of the primary colon cancer has no impact on outcomes in patients undergoing cytoreductive surgery for peritoneal metastasis

BACKGROUND

The impact of the location of colorectal cancer on patient outcomes has been reported in several settings. The objective of this study was to assess the prognostic impact of the location of the primary colon cancer among patients with colorectal cancer peritoneal metastases undergoing complete cytoreductive surgery.

METHODS

Using the prospectively maintained clinical and biological digestive peritoneal metastasis database of the BIG-RENAPE network, we identified 796 patients treated by a complete cytoreductive surgery between January 2004 and January 2017 for colorectal cancer peritoneal metastases in 16 different institutions. The 2 primary endpoints were overall survival and progression-free survival. To evaluate the impact on overall survival and progression-free survival of potential prognostic factors (including the location of the primary colorectal cancer), these factors were included in univariate and multivariate Cox proportional hazard models.

RESULTS

Right-sided colorectal cancers were more often BRAF mutated and had microsatellite instability, whereas the frequency of RAS mutation was similar between right-sided and left-sided colorectal cancers. After a median follow-up time of 3.3 years, there was no significant difference in overall survival or progression-free survival according to tumor side. The lack of effect of tumor location on overall survival and progression-free survival was consistent across subgroups.

CONCLUSION

Among patients undergoing complete cytoreductive surgery for peritoneal metastases, the site of the primary colorectal cancer was not associated with differences in progression-free survival or overall survival. Tumor side should not be used as a stratification factor in trials of colorectal cancer peritoneal metastases and should not be used in the selection process of patients for cytoreductive surgery.

TP53 Gene Pro72Arg (rs1042522) Single Nucleotide Polymorphism as Not a Risk Factor for Colorectal Cancer in the Iranian Azari Population

Background:

The p53 protein participates critically in several cellular functions such as cell growth and DNA repair. Polymorphisms in the TP53locus have repeatedly been implicated in the pathogenesis of cancers all over the world. Over 200 single nucleotide polymorphisms (SNPs) have been characterized, but one well-known example at at codon 72, Pro72Arg(rs1042522), has the displayed inconsistent results with regard to cancer risk. Herein, we aimed to evaluate whether Pro72Arg(rs1042522) single nucleotide polymorphism (SNP) in TP53gene might be associated with risk of colorectal cancer in the Iranian Azari population.

Methods:

Blood samples were taken from 100 healthy controls and 100 colorectal cancer patients with Iranian-Azeri ethnicity. Genotyping was performed with Tetra-ARMS PCR.

Results:

The alleles of the TP53gene Pro72ArgSNP did not significantly differ in prevalence between patients and controls (P>0.05). Additionally, genotypes of Pro72ArgSNP were not significantly associated with colorectal cancer risk in the studied population.

Conclusions:

Pro72ArgSNP of TP53gene may not be involved in the disease pathogenesis in Iranian Azari patients with colorectal cancer.

The prognostic significance of protein arginine methyltransferase 6 expression in colon cancer

Protein arginine methylation is involved in cellular differentiation and proliferation. Recently, aberrant expression of protein arginine methyltransferases, which are responsible for the methylation reaction, has been reported in various types of cancer. However, there is no clear evidence regarding the prognostic value of abnormal PRMT6 expression in colorectal cancer or the effect of PRMT6 regulation on CRC cells. We investigated the expression patterns of PRMT6 in patients with stage II and III CRC. We detected nuclear expression of PRMT6 in 23.7% of carcinoma samples by immunohistochemistry. Among the clinicopathological parameters, the ratio of poorly differentiated cancer cells was approximately two-fold higher in patients with PRMT6-positive disease than in those with PRMT6-negative disease (p = 0.002). Patients with PRMT6-positive CRC had a shorter disease-free survival than those with PRMT6-negative CRC in both univariate and multivariate analyses (p = 0.018 and p = 0.035, respectively). siRNA-mediated inhibition of PRMT6 expression in CRC cells induced p21^WAF1/CIP1 overexpression and suppressed cell growth and colony-forming ability. Concomitantly, apoptosis was induced in PRMT6-suppressed CRC cells. These data suggest that PRMT6 can serve as a biomarker for unfavorable prognosis and as a therapeutic target in CRC.

The predictive effect of primary tumour location in the treatment of metastatic colorectal cancer: a Canadian consensus statement

In recently published data, the predictive value of primary tumour location for the treatment of metastatic colorectal cancer with available biologic therapies has been explored. Recognizing the potential effect of those data on clinical practice, we convened a meeting of Canadian experts who treat metastatic colorectal cancer to develop a set of national, evidence-based treatment guidelines based on primary tumour location. This report summarizes the relevant evidence and presents the consensus recommendations of those experts.

The predictive value of primary tumor location in patients with metastatic colorectal cancer: A systematic review

Colorectal cancer (CRC) is one of the most frequently diagnosed cancers worldwide. It has been reported that left- and right-sided CRC harbor varying disease characteristics, which leads to a difference in prognosis and response to therapy. Recently, there have been retrospective studies about tumor location in metastatic CRC (mCRC) and its potential to predict the effect of anti-vascular endothelial growth factor and anti-epidermal growth factor receptor (anti-EGFR) therapies. In this review, we provide a comprehensive overview of the latest trials studying the predictive value of primary tumor location in mCRC and discuss biomarkers that might be associated with the differences in treatment response. Although data need to be interpreted with caution due to the absence of randomized trials stratified based on tumor location, patients with left-sided CRC seem to benefit more from anti-EGFR therapy than patients with right-sided CRC. Further clinical trials, stratified for tumor location, are warranted.

Association Between Prognosis and Tumor Laterality in Early-Stage Colon Cancer

IMPORTANCE

Recent data have suggested that disease biology and outcome of colon cancer may differ between right-sided and left-sided tumors. However, the literature on the prognostic value of tumor laterality is conflicting.

OBJECTIVE

To explore differences in laterality based on disease characteristics and outcomes in a population-based cohort of early-stage colon cancer.

DESIGN, SETTING, AND PARTICIPANTS

This investigation was a population-based retrospective cohort study of patients with early-stage colon cancer from the province of Ontario, Canada. Electronic records of treatment were linked to the Ontario Cancer Registry to identify all patients with colon cancer who underwent resection between January 1, 2002, and December 31, 2008. The date of the final analysis was October 20, 2016. The study population included a 25% random sample of all patients with resected stage I to III disease. Right-sided colon cancer was defined as any tumor arising in the cecum, ascending colon, hepatic flexure, or transverse colon. Left-sided colon cancer was defined as any tumor arising in the splenic flexure, descending colon, sigmoid colon, or rectosigmoid colon.

MAIN OUTCOMES AND MEASURES

Overall survival (OS) and cancer-specific survival (CSS) measured from the time of resection.

RESULTS

This study identified 6365 patients with early-stage colon cancer (48.7% [3098 of 6365] female). Their median age was 72 years, and 51.7% (3291 of 6365) had right-sided disease. Stage distribution was 18.3% (1163 of 6365) stage I, 38.4% (2446 of 6365) stage II, and 43.3% (2756 of 6365) stage III. Patients with right-sided colon cancer were more likely to be older (median age, 73 vs 70 years; P < .001) and female (54.4% [1790 of 3291] vs 42.6% [1308 of 3074], P < .001) and have greater comorbidity. Right-sided cancers were more likely to be T4 (19.2% [631 of 3291] vs 15.9% [490 of 3074], P < .001) and poorly differentiated (21.1% [695 of 3291] vs 9.6% [295 of 3074], P < .001) but less likely to be node positive (42.0% [1383 of 3291] vs 44.7% [1373 of 3074], P = .03) compared with left-sided disease. In adjusted analyses, there was no difference in long-term survival for right-sided compared with left-sided colon cancer: the hazard ratios were 1.00 (95% CI, 0.92-1.08) for OS and 1.00 (95% CI, 0.91-1.10) for CSS. These results were consistent when the survival analyses were restricted to stage III disease: the hazard ratios were 1.03 (95% CI, 0.93-1.14) for OS and 1.10 (95% CI, 0.97-1.24) for CSS.

CONCLUSIONS AND RELEVANCE

In this population-based cohort of early-stage resected colon cancer, disease laterality was not associated with long-term OS or CSS.

Global metabolic reprogramming of colorectal cancer occurs at adenoma stage and is induced by MYC

Cancer cells alter their metabolism for the production of precursors of macromolecules. However, the control mechanisms underlying this reprogramming are poorly understood. Here we show that metabolic reprogramming of colorectal cancer is caused chiefly by aberrant MYC expression. Multiomics-based analyses of paired normal and tumor tissues from 275 patients with colorectal cancer revealed that metabolic alterations occur at the adenoma stage of carcinogenesis, in a manner not associated with specific gene mutations involved in colorectal carcinogenesis. MYC expression induced at least 215 metabolic reactions by changing the expression levels of 121 metabolic genes and 39 transporter genes. Further, MYC negatively regulated the expression of genes involved in mitochondrial biogenesis and maintenance but positively regulated genes involved in DNA and histone methylation. Knockdown of MYC in colorectal cancer cells reset the altered metabolism and suppressed cell growth. Moreover, inhibition of MYC target pyrimidine synthesis genes such as CAD, UMPS, and CTPS blocked cell growth, and thus are potential targets for colorectal cancer therapy.

Molecular Characterization of Somatic Alterations in Dukes' B and C Colorectal Cancers by Targeted Sequencing

Despite global progress in research, improved screening and refined treatment strategies, colorectal cancer (CRC) remains as the third most common malignancy. As each type of cancer is different and exhibits unique alteration patterns, identifying and characterizing gene alterations in CRC that may serve as biomarkers might help to improve diagnosis, prognosis and predict potential response to therapy. With the emergence of next generation sequencing technologies (NGS), it is now possible to extensively and rapidly identify the gene profile of individual tumors. In this study, we aimed to identify actionable somatic alterations in Dukes’ B and C in CRC via NGS. Targeted sequencing of 409 cancer-related genes using the Ion Ampliseq^TM Comprehensive Cancer Panel was performed on genomic DNA obtained from paired fresh frozen tissues, cancer and normal, of Dukes’ B (n = 10) and Dukes’ C (n = 9) CRC. The sequencing results were analyzed using Torrent Suite, annotated using ANNOVAR and validated using Sanger sequencing. A total of 141 somatic non-synonymous sequence variations were identified in 86 genes. Among these, 64 variants (45%) were predicted to be deleterious, 38 variants (27%) possibly deleterious while the other 39 variants (28%) have low or neutral protein impact. Seventeen genes have alterations with frequencies of ≥10% in the patient cohort and with 14 overlapped genes in both Dukes’ B and C. The adenomatous polyposis coli gene (APC) was the most frequently altered gene in both groups (n = 6 in Dukes’ B and C). In addition, TP53 was more frequently altered in Dukes’ C (n = 7) compared to Dukes’ B (n = 4). Ten variants in APC, namely p.R283^∗, p.N778fs, p.R805^∗, p.Y935fs, p.E941fs, p.E1057^∗, p.I1401fs, p.Q1378^∗, p.E1379^∗, and p.A1485fs were predicted to be driver variants. APC remains as the most frequently altered gene in the intermediate stages of CRC. Wnt signaling pathway is the major affected pathway followed by P53, RAS, TGF-β, and PI3K signaling. We reported the alteration profiles in each of the patient which has the potential to affect the clinical decision. We believe that this study will add further to the understanding of CRC molecular landscape.

Association between mutations of critical pathway genes and survival outcomes according to the tumor location in colorectal cancer

BACKGROUND

Colorectal cancer (CRC) develops through the alteration of several critical pathways. This study was aimed at evaluating the influence of critical pathways on survival outcomes for patients with CRC.

METHODS

Targeted next-generation sequencing of 40 genes included in the 5 critical pathways of CRC (WNT, P53, RTK-RAS, phosphatidylinositol-4,5-bisphosphate 3-kinase [PI3K], and transforming growth factor β [TGF-β]) was performed for 516 patients with stage III or high-risk stage II CRC treated with surgery followed by adjuvant fluoropyrimidine and oxaliplatin chemotherapy. The associations between critical pathway mutations and relapse-free survival (RFS) and overall survival were analyzed. The associations were further analyzed according to the tumor location.

RESULTS

The mutation rates for the WNT, P53, RTK-RAS, PI3K, and TGF-β pathways were 84.5%, 69.0%, 60.7%, 30.0%, and 28.9%, respectively. A mutation in the PI3K pathway was associated with longer RFS (adjusted hazard ratio [HR], 0.59; 95% confidence interval [CI], 0.36-0.99), whereas a mutation in the RTK-RAS pathway was associated with shorter RFS (adjusted HR, 1.60; 95% CI, 1.01-2.52). Proximal tumors showed a higher mutation rate than distal tumors, and the mutation profile was different according to the tumor location. The mutation rates of Kirsten rat sarcoma viral oncogene homolog (KRAS), phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit α (PIK3CA), and B-Raf proto-oncogene serine/threonine kinase (BRAF) were higher in proximal tumors, and the mutation rates of adenomatous polyposis coli (APC), tumor protein 53 (TP53), and neuroblastoma RAS viral oncogene homolog (NRAS) were higher in distal tumors. The better RFS with the PI3K pathway mutation was significant only for proximal tumors, and the worse RFS with the RTK-RAS pathway mutation was significant only for distal tumors.

CONCLUSIONS

A PI3K pathway mutation was associated with better RFS for CRC patients treated with adjuvant chemotherapy, and an RTK-RAS pathway mutation was associated with worse RFS. The significance of the prognostic impact differed according to the tumor location. Cancer 2017;123:3513-23. © 2017 American Cancer Society.

Distribution of KRAS and BRAF Mutations in Metastatic Colorectal Cancers in Turkish Patients

The results of this study demonstrate the potential prognostic and predictive values of KRAS and BRAF gene mutations in patients with colorectal cancer (CRC). It has been proven that KRAS and BRAF mutations are predictive biomarkers for resistance to anti-EGFR monoclonal antibody treatment in patients with metastatic CRC (mCRC). We demonstrated the distribution of KRAS (codons 12, 13 and 61) and BRAF (codon 600) gene mutations in 50 mCRCs using direct sequencing and compared the results with clinicopathological data. KRAS and BRAF mutations were identified in 15 (30%) and 1 (2%) patients, respectively. We identified KRAS mutations in codon 12, 13 and 61 in 73.3% (11/15), 20% (3/15) and 6.67% (1/15) of the positive patients, respectively. The KRAS mutation frequency was significantly higher in tumors located in the ascending colon (p=0.043). Thus, we found that approximately 1/3 of the patients with mCRC had KRAS mutations and the only clinicopathological factor related to this mutation was tumor location. Future studies with larger patient groups should yield more accurate data regarding the molecular mechanism of CRC and the association between KRAS and BRAF mutations and clinicopathological features.

Paradoxical Reductions in Serum Anti-p53 Autoantibody Levels by Chemotherapy in Unresectable Colorectal Cancer: An Observational Study

OBJECTIVE

The anti-p53 autoantibody is an emerging tumor marker that is commonly produced in response to p53 mutations. The usefulness of this antibody has been suggested in screening for and the monitoring of recurrence in colorectal cancer; however, its significance as a marker during chemotherapy remains largely unknown.

METHODS

We measured serum anti-p53 antibody levels in patients with unresectable colorectal cancer who underwent first-line systemic chemotherapy. Tumor responses were evaluated by computed tomography. We determined whether temporal changes in this antibody during therapy are associated with radiological responses.

RESULTS

Of the 83 patients in our study, 29 (35%) had elevated serum anti-p53 antibody levels before chemotherapy. Among these, antibody levels decreased in all 14 responders. In contrast, among those patients with elevated pretherapeutic serum anti-p53 antibody levels, 89% showed a paradoxical decrease in antibody levels and exhibited disease progression after chemotherapy. Moreover, serum anti-p53 antibody levels before and after chemotherapy were not associated with survival.

CONCLUSION

These results suggest that serum anti-p53 antibody levels are of limited value in the evaluation of responses to palliative chemotherapy in patients with colorectal cancer.

TP53 Mutational Analysis Enhances the Prognostic Accuracy of IHC4 and PAM50 Assays

IHC4 and PAM50 assays have been shown to provide additional prognostic information for patients with early breast cancer. We evaluated whether incorporating TP53 mutation analysis can further enhance their prognostic accuracy. We examined TP53 mutation and the IHC4 score in tumors of 605 patients diagnosed with stage I-III breast cancer at National Taiwan University Hospital (the NTUH cohort). We obtained information regarding TP53 mutation and PAM50 subtypes in 699 tumors from the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) cohort. We found that TP53 mutation was significantly associated with high-risk IHC4 group and with luminal B, HER2-enriched, and basal-like subtypes. Despite the strong associations, TP53 mutation independently predicted shorter relapse-free survival (hazard ratio [HR] = 1.63, P = 0.007) in the NTUH cohort and shorter breast cancer-specific survival (HR = 2.35, P = <0.001) in the METABRIC cohort. TP53 mutational analysis added significant prognostic information in addition to the IHC4 score (∆ LR-χ(2) = 8.61, P = 0.002) in the NTUH cohort and the PAM50 subtypes (∆ LR-χ(2) = 18.9, P = <0.001) in the METABRIC cohort. We conclude that incorporating TP53 mutation analysis can enhance the prognostic accuracy of the IHC4 and PAM50 assays.

Serum anti-p53 antibody as a tumour marker for colorectal cancer screening

A 60-year-old Japanese man presented to our hospital for further investigation of an elevated serum anti-p53 antibody level. He was diagnosed with colon cancer and the tumour was surgically resected. Histological diagnosis of advanced colon cancer without lymph node involvement or distant metastasis was made. It was noteworthy that both serum carcinoembryonic antigen (CEA) and a fecal occult blood test that were performed preoperatively were non-diagnostic. This case highlights the potential usefulness of serum anti-p53 antibody tests for detection of colorectal cancers. Moreover, sequential changes in the anti-p53 antibody levels after curative resection were observed.

Genetic mutations in human rectal cancers detected by targeted sequencing

Colorectal cancer (CRC) is widespread with significant mortality. Both inherited and sporadic mutations in various signaling pathways influence the development and progression of the cancer. Identifying genetic mutations in CRC is important for optimal patient treatment and many approaches currently exist to uncover these mutations, including next-generation sequencing (NGS) and commercially available kits. In the present study, we used a semiconductor-based targeted DNA-sequencing approach to sequence and identify genetic mutations in 91 human rectal cancer samples. Analysis revealed frequent mutations in KRAS (58.2%), TP53 (28.6%), APC (16.5%), FBXW7 (9.9%) and PIK3CA (9.9%), and additional mutations in BRAF, CTNNB1, ERBB2 and SMAD4 were also detected at lesser frequencies. Thirty-eight samples (41.8%) also contained two or more mutations, with common combination mutations occurring between KRAS and TP53 (42.1%), and KRAS and APC (31.6%). DNA sequencing for individual cancers is of clinical importance for targeted drug therapy and the advantages of such targeted gene sequencing over other NGS platforms or commercially available kits in sensitivity, cost and time effectiveness may aid clinicians in treating CRC patients in the near future.

Is right-sided colon cancer different to left-sided colorectal cancer? - a systematic review

Colorectal cancer (CRC) exhibits differences in incidence, pathogenesis, molecular pathways and outcome depending on the location of the tumor. This review focuses on the latest developments in epidemiological and scientific studies, which have enhanced our understanding on the underlying genetic and immunological differences between the proximal (right-sided) colon and the distal (left-sided) colorectum. The different ways in which environmental risk factors influence the pathogenesis of CRC depending on its location and the variations in surgical and oncological outcomes are also discussed in this review. In the current era of personalized medicine, we aim to reiterate the importance of tumor location in management of CRC and the implication on future clinical and scientific research.

Implication of K-ras and p53 in colorectal cancer carcinogenesis in Tunisian population cohort

According to the multistep route of genetic alterations in the colorectal adenoma-carcinoma sequence, the complex K-ras/p53 mutation is one of the first alterations to occur and represent an important genetic event in colorectal cancer (CRC). An evaluation of the mutation spectra in K-ras and p53 gene was effected in 167 Tunisian patients with sporadic CRC to determine whether our populations have similar pattern of genetic alteration as in Maghrebin's population. Mutation patterns of codon 12-13 of K-ras and exon 5-8 of p53 were analyzed by immunohistochemistry and PCR-SSCP and confirmed by sequencing. Mutations in the K-ras gene were detected in 31.13 % and affect the women more than the men (p = 0.008). Immunostaining showed that expression of p21 ras was correlated with the advanced age (p = 0.004), whereas loss of signal was associated with mucinous histotype (p = 0.003). Kaplan-Meier survival curve found that patients with the K-ras mutation had a shorter survival compared with patients without mutation (p = 0.005). Alteration in p53 was seen in 17.4 % of patients and affects three hot spot codons such as 175, 245, and 248. Overexpression of p53 was seen in 34.1 % and correlated with tumor node metastasis (TNM) advanced stage (p = 0.037) and mucinous histotype (p = 0.001). A high concordance between p53 expression and alteration (p<0.005) was shown. Concomitant mutations in K-ras and p53 gene were detected in only 4 % of tumors. K-ras and p53 undergo separate pathways in colorectal tumorogenesis. Interestingly, mutations in the K-ras gene might be considered a valuable prognostic factor correlated to poor outcome. p53 gene alterations were rather low in our set, and methylation pattern of p53 is required to elucidate the molecular basis of this protein in CRC.

Characterization of rare transforming KRAS mutations in sporadic colorectal cancer

KRAS mutational status has been shown to be a predictive biomarker of resistance to anti-EGFR monoclonal antibody (mAb) therapy in patients with metastatic colorectal cancer. We report the spectrum of KRAS mutation in 1506 patients with colorectal cancer and the identification and characterization of rare insertion mutations within the functional domain of KRAS. KRAS mutations are found in 44.5% (670/1506) of the patients. Two cases are found to harbor double mutations involving both codons 12 and 13. The frequencies of KRAS mutations at its codons 12, 13, 61, and 146 are 75.1%, 19.3%, 2.5%, and 2.7%, respectively. The most abundant mutation of codon 12 is G12D, followed by G12V and G12C while G13D is the predominant mutation in codon 13. Mutations in other codons are rare. The KRAS mutation rate is significantly higher in women (48%, 296/617) than in men (42.1%, 374/889, P = 0.023). Tumors on the right colon have a higher frequency of KRAS mutations than those on the left (57.3% vs. 40.4%, P < 0.0001). Two in-frame insertion mutations affect the phosphate-binding loop (codon 10–16) of KRAS are identified. One of them has never been reported before. Compared with wild-type protein, the insertion variants enhance the cellular accumulation of active RAS (RAS-GTP) and constitutively activate the downstream signaling pathway. NIH3T3 cells transfected with the insertion variants show enhanced anchorage-independent growth and in vivo tumorigenicity. Potentially these mutations contribute to primary resistance to anti-EGFR mAb therapy but the clinical implication requires further validation.

Microenvironment influence on human colon adenocarcinoma phenotypes and matrix metalloproteinase-2, p53 and β-catenin tumor expressions from identical monoclonal cell tumor in the orthotopic model in athymic nude rats

The present study aims to identify differences between left and right colon adenocarcinoma arising from identical clonal cell and to find out if microenvironment has any influence on matrix metalloproteinase-2 (MMP2), p53 and β-catenin tumor expressions. MATERIAL AND METHODS. Rats (RNU) were submitted to cecostomy to obtain the orthotopic model of right colon tumor (n = 10), while for the left colon model (n = 10), a colon diversion and distal mucous fistula in the descending colon was used. Cultivated human colon adenocarcinoma cells (WiDr) were inoculated in stomas submucosa. Histopathological analysis, real-time reverse transcription-PCR for β-catenin, p53 and MMP2, as well as immunohistochemical analysis for p53 and β-catenin expression were conducted. Central tendency, variance analysis and the Livak delta-delta-CT method were used for statistical analysis, adopting a 5% significance level. RESULTS. All tumors from the left colon exhibited infiltrative ulceration, while in the right colon tumor growth was predominantly exophytic (67%). In the left colon, tumor growth was undifferentiated (100%), while it was moderately differentiated in the right colon (83%). In right colon tumors, MMP2, p53, and β-catenin gene expressions were higher than compared to left colon (p = 4.59354E-05, p = 0.0035179, p = 0.00093798, respectively, for MMP2, p53 and β-catenin). β-catenin and p53 results obtained by real-time polymerase chain reaction were confirmed by immunohistochemistry assay (p = 0.01 and p = 0.001, respectively, for β-catenin and p53). CONCLUSION. Left and right human colon adenocarcinomas developed in animal models have distinct phenotypes even when they have the same clonal origin. Microenvironment has influenced p53, β-catenin, and MMP2 expression in animal models of colon cancer.

Gene and isoform expression signatures associated with tumor stage in kidney renal clear cell carcinoma

Background

Identification of expression alternations between early and late stage cancers is helpful for understanding cancer development and progression. Much research has been done focusing on stage-dependent gene expression profiles. In contrast, relatively fewer studies on isoform expression profiles have been performed due to the difficulty of quantification and noisy splicing. Here we conducted both gene- and isoform-level analysis on RNA-seq data of 234 stage I and 81 stage IV kidney renal clear cell carcinoma patients, aiming to uncover the stage-dependent expression signatures and investigate the advantage of isoform expression profiling for identifying advanced stage cancers and predicting clinical outcome.

Results

Both gene and isoform expression signatures are useful for distinguishing cancer stages. They provide common and unique information associated with cancer progression and metastasis. Combining gene and isoform signatures even improves the classification performance and reveals additional important biological processes, such as angiogenesis and TGF−beta signaling pathway. Moreover, expression abundance of a number of genes and isoforms is predictive of the risk of cancer death in an independent dataset, such as gene and isoform expression of ITPKA, the expression of a functional important isoform of UPS19.

Conclusion

Isoform expression profiling provides unique and important information which cannot be detected by gene expression profiles. Combining gene and isoform expression signatures helps to identify advanced stage cancers, predict clinical outcome, and present a comprehensive view of cancer development and progression.

Somatic profiling of the epidermal growth factor receptor pathway in tumors from patients with advanced colorectal cancer treated with chemotherapy ± cetuximab

PURPOSE

To study the somatic molecular profile of the EGF receptor (EGFR) pathway in advanced colorectal cancer, its relationship to prognosis, the site of the primary and metastases, and response to cetuximab.

EXPERIMENTAL DESIGN

We used Sequenom and Pyrosequencing for high-throughput somatic profiling of the EGFR pathway in 1,976 tumors from patients with advanced colorectal cancer from the COIN trial (oxaliplatin and fluoropyrimidine chemotherapy ± cetuximab). Correlations between mutations, clinicopathologic, response, and survival data were carried out.

RESULTS

Sequenom and Pyrosequencing had 99.0% (9,961/10,063) genotype concordance. We identified 13 different KRAS mutations in 42.3% of advanced colorectal cancers, 2 BRAF mutations in 9.0%, 4 NRAS mutations in 3.6%, and 5 PIK3CA mutations in 12.7%. 4.2% of advanced colorectal cancers had microsatellite instability (MSI). KRAS and PIK3CA exon 9, but not exon 20, mutations cooccurred (P = 8.9 × 10(-4)) as did MSI and BRAF mutations (P = 5.3 × 10(-10)). KRAS mutations were associated with right colon cancers (P = 5.2 × 10(-5)) and BRAF mutations with right (P = 7.2 × 10(-5)) and transverse colon (P = 9.8 × 10(-6)) cancers. KRAS mutations were associated with lung-only metastases (P = 2.3 × 10(-4)), BRAF mutations with peritoneal (P = 9.2 × 10(-4)) and nodal-only (P = 3.7 × 10(-5)) metastases, and MSI (BRAF(WT)) with nodal-only metastases (P = 2.9 × 10(-4)). MSI (BRAF(WT)) was associated with worse survival (HR = 1.89, 95% CI 1.30-2.76, P = 8.5 × 10(-4)). No mutations, subsets of mutations, or MSI status were associated with response to cetuximab.

CONCLUSIONS

Our data support a functional cooperation between KRAS and PIK3CA in colorectal tumorigenesis and link somatic profiles to the sites of metastases. MSI was associated with poor prognosis in advanced disease, and no individual somatic profile was associated with response to cetuximab in COIN.

Prognostic role of p53 messenger ribonucleic acid expression in patients after curative resection for stage I to III colorectal cancer: association with colon cancer stem cell markers

BACKGROUND

The current study was performed to examine the prognostic role of 53 messenger ribonucleic acid (mRNA) expression in patients with colorectal cancer and analyze its relationship with the expression of CD44 and CD133 mRNA levels.

STUDY DESIGN

We retrospectively reviewed 137 consecutive patients who underwent curative surgery for stage I to III colorectal cancer in 2006. Prognostic factors, including wild-type (wt) p53, cyclooxygenase-2, CD44, and CD133 mRNA levels, were determined using reverse transcriptase polymerase chain reaction and clinical outcomes were analyzed.

RESULTS

Wild-type p53 mRNA expression was correlated with the expression of CD44 and CD133 mRNA (p = 0.005 and p = 0.013, respectively). With a median follow-up period of 64 months, the 5-year disease-free survival rate of patients with elevated wt-p53 mRNA expression was significantly higher than that of those patients with low levels of wt-p53 mRNA expression (84.9% and 67.6%, respectively; p = 0.014). A multivariate analysis identified 3 independent factors that substantially affected the disease-free survival: depth of tumor invasion, lymph node metastasis, and wt-p53 mRNA expression. The 5-year disease-free survival rate in patients with stage III or rectal tumors differed significantly between the low and high wt-p53 expression groups. In stage III cancers, high wt-p53 expression was associated with better survival than low wt-p53 expression in patients treated with adjuvant chemotherapy (p = 0.005). A significant association between combined p53/CD44 expression and survival was evident (p = 0.006).

CONCLUSIONS

Expression of p53 mRNA is a useful predictor of survival in patients with stage III or rectal cancers, with a significant association with CD44 mRNA expression.

Alterations in K-ras, APC and p53-multiple genetic pathway in colorectal cancer among Indians

The incidence of colorectal cancer (CRC) is increasing rapidly in Asian countries during the past few decades, but no comprehensive analysis has been done to find out the exact cause of this disease. In this study, we investigated the frequencies of mutations and expression pattern of K-ras, APC (adenomatosis polyposis coli) and p53 in tumor, adjoining and distant normal mucosa and to correlate these alterations with patients clinicopathological parameters as well as with the survival. Polymerase chain reaction (PCR)-restriction digestion was used to detect mutations in K-ras and PCR-SSCP (Single Strand Conformation Polymorphism) followed by DNA sequencing was used to detect mutations in APC and p53 genes. Immunohistochemistry was used to detect the expression pattern of K-ras, APC and p53 proteins. The frequencies of mutations of K-ras, APC and p53 in 30 tumor tissues samples were 26.7 %, 46.7 % and 20 %, respectively. Only 3.3 % of tumors contained mutations in all the three genes. The most common combination of mutation was APC and p53 whereas mutation in both p53 and K-ras were extremely rare. There was no association between the mutations and expression pattern of K-ras, APC and p53 (p>0.05). In Indians, the frequency of alterations of K-ras and APC is similar as in Westerns, whereas the frequency of p53 mutation is slightly lower. The lack of multiple mutations in tumor specimens suggests that these genetic alterations might have independent influences on CRC development and there could be multiple alternative genetic pathways to CRC in our present study cohort.

Molecular alterations in colitis-associated colorectal neoplasia: study from a low prevalence area using magnifying chromo colonoscopy

BACKGROUND AND AIM

Longstanding ulcerative colitis (UC) predisposes to colorectal cancer (CRC). To understand the molecular pathogenesis of colitis-associated colorectal neoplasia (UC-CRN), we studied the frequency of microsatellite instability (MSI) and mutations in p53, BRAF and KRAS genes in the tissues of patients with long standing UC with or without neoplasia and compared them with colitis patients without risk of neoplasia, and those with sporadic colorectal neoplasia (S-CRN) in an area with lower prevalence for either disease.

METHODS

Biopsies were obtained during magnifying chromo colonoscopy or routine colonoscopy in consecutive UC patients with high risk (UC-HR) and low risk (UC-LR) of neoplasia, and those with S-CRN. MSI (NCI-Bethesda panel) and mutations in p53, KRAS and BRAF genes were analysed.

RESULTS

Twenty-eight patients with UC-HR, 30 with UC-LR and 30 with S-CRN were included. Six (21.4%) of UC-HR had neoplasia (Progressors). MSI was not detected in the UC-CRN group as compared to 5 (16.7%) in the S-CRN group. p53 mutations occurred in 1 (3.3%) of UC-LR, increasing to 6 (27.3%, P<0.05) and 3 (50%, P<0.05) in the UC-HR subgroups without and with neoplasia respectively, as against 10 (33.3%) in sporadic neoplasia group. KRAS mutations were found only in the presence of neoplasia. None showed the BRAF mutation.

CONCLUSIONS

In a population with a lower prevalence for UC and CRC, the molecular pathogenesis of colitis-associated colorectal neoplasia is comparable to that reported from areas with a higher prevalence of these diseases, MSI being an exception.

Villin expression is frequently lost in poorly differentiated colon cancer

Colorectal cancers (CRCs) are classified as having microsatellite instability (MSI) or chromosomal instability (CIN); herein termed microsatellite stable (MSS). MSI colon cancers frequently display a poorly differentiated histology for which the molecular basis is not well understood. Gene expression and immunohistochemical profiling of MSS and MSI CRC cell lines and tumors revealed significant down-regulation of the intestinal-specific cytoskeletal protein villin in MSI colon cancer, with complete absence in 62% and 17% of MSI cell lines and tumors, respectively. Investigation of 577 CRCs linked loss of villin expression to poorly differentiated histology in MSI and MSS tumors. Furthermore, mislocalization of villin from the membrane was prognostic for poorer outcome in MSS patients. Loss of villin expression was not due to coding sequence mutations, epigenetic inactivation, or promoter mutation. Conversely, in transient transfection assays villin promoter activity reflected endogenous villin expression, suggesting transcriptional control. A screen of gut-specific transcription factors revealed a significant correlation between expression of villin and the homeobox transcription factor Cdx-1. Cdx-1 overexpression induced villin promoter activity, Cdx-1 knockdown down-regulated endogenous villin expression, and deletion of a key Cdx-binding site within the villin promoter attenuated promoter activity. Loss of Cdx-1 expression in CRC lines was associated with Cdx-1 promoter methylation. These findings demonstrate that loss of villin expression due to Cdx-1 loss is a feature of poorly differentiated CRCs.

p53 mutation is common in microsatellite stable, BRAF mutant colorectal cancers

The majority of "serrated pathway" colorectal cancers have mutation of the BRAF oncogene and display the CpG island methylator phenotype (CIMP). Half these cancers have microsatellite instability (MSI) and an excellent prognosis. In the absence of MSI (microsatellite stable, MSS), BRAF mutation has been associated with a particularly poor prognosis. "Traditional pathway" cancers are BRAF wild type. Mutation of p53 is common and this correlates with advanced stage. We therefore hypothesized that p53 mutation would be common in MSS/BRAF mutant colorectal cancer. One thousand and eighty-one colorectal cancers were screened for BRAF mutation to identify two BRAF mutant study groups (MSI: n = 77; MSS: n = 69) and a BRAF wild type control group (n = 101). These were screened for p53 mutation by high resolution melt analysis and classified for CIMP and MGMT methylation by quantitative methylation specific PCR. Molecular data were compared to patient age, gender, tumor location and stage. p53 was mutated significantly more frequently in MSS/BRAF mutant (28/69, 40.6%) compared to MSI/BRAF mutant cancers (13/77, 16.9%), but this mutation rate did not differ from MSS/BRAF wild type cancers (47/101, 46.5%)(p < 0.0001). CIMP was less common in MSS/BRAF mutant (26/47, 55.3%) compared to MSI/BRAF mutant cancers (41/54, 75.9%), but was more common than in MSS/BRAF wild type cancers (3/85, 3.5%) (p < 0.0001). MSS/BRAF mutant cancers were more commonly proximal (38/54, 70.3%), but were similar to MSS/BRAF wild type cancers in terms of patient age, gender distribution and stage at presentation. MSS/BRAF mutant cancers share molecular and clinical features of both the serrated and traditional pathways of colorectal tumorigenesis.

Pyrosequencing-based methods reveal marked inter-individual differences in oncogene mutation burden in human colorectal tumours

Background:

The epidermal growth factor receptor-targeted monoclonal antibody cetuximab (Erbitux) was recently introduced for the treatment of metastatic colorectal cancer. Treatment response is dependent on Kirsten-Ras (K-Ras) mutation status, in which the majority of patients with tumour-specific K-Ras mutations fail to respond to treatment. Mutations in the oncogenes B-Raf and PIK3CA (phosphoinositide-3-kinase) may also influence cetuximab response, highlighting the need for a sensitive, accurate and quantitative assessment of tumour mutation burden.

Methods:

Mutations in K-Ras, B-Raf and PIK3CA were identified by both dideoxy and quantitative pyrosequencing-based methods in a cohort of unselected colorectal tumours (n=102), and pyrosequencing-based mutation calls correlated with various clinico-pathological parameters.

Results:

The use of quantitative pyrosequencing-based methods allowed us to report a 13.7% increase in mutation burden, and to identify low-frequency (<30% mutation burden) mutations not routinely detected by dideoxy sequencing. K-Ras and B-Raf mutations were mutually exclusive and independently associated with a more advanced tumour phenotype.

Conclusion:

Pyrosequencing-based methods facilitate the identification of low-frequency tumour mutations and allow more accurate assessment of tumour mutation burden. Quantitative assessment of mutation burden may permit a more detailed evaluation of the role of specific tumour mutations in the pathogenesis and progression of colorectal cancer and may improve future patient selection for targeted drug therapies.

Molecular diagnosis of response to neoadjuvant chemoradiation therapy in patients with locally advanced rectal cancer

BACKGROUND

Pathologic complete response (pCR) to neoadjuvant chemoradiation (CRT) is an important prognostic factor in locally advanced rectal cancer. However, it is uncertain if histopathological techniques accurately detect pCR. We tested a novel molecular approach for detecting pCR and compared it with current histopathological approaches.

STUDY DESIGN

Pretreatment tumor biopsies and surgical specimens were collected from 96 patients with locally advanced rectal cancer treated with neoadjuvant CRT and surgery. Tumor response was categorized by tumor regression grade. Tumor DNA from pre-CRT tumor biopsies was screened for K-ras and p53 mutations. DNA from paired surgical specimens was then screened for the same mutations using highly sensitive polymerase chain reaction-based techniques.

RESULTS

Sixty-eight of 96 (71%) pretreatment biopsies harbored K-ras and/or p53 mutation; 36 (38%) had K-ras mutations, 52 (54%) had p53 mutations, and 20 (21%) carried both mutations. Of 70 patients with tumor regression grades 1 to 3, sixty-six (94%) had a concordant K-ras and p53 mutation profile in pre- and post-treatment tissues. Of 26 patients with tumor regression grade 0 (pCR), 12 had K-ras or p53 mutations in pretreatment biopsies. Of these, 2 (17%) patients had the same K-ras (n = 1) or p53 (n = 1) mutation detected in post-treatment tissue.

CONCLUSIONS

Sensitive molecular techniques detect K-ras and p53 mutations in post-CRT surgical specimens in some patients with a pCR. This suggests histopathological techniques might not be completely accurate, and some patients diagnosed with a pCR to CRT might have occult cancers cells in their surgical specimens.

Chromosomal copy number alterations are associated with tumor response to chemoradiation in locally advanced rectal cancer

Rectal cancer response to chemoradiation (CRT) varies from no response to a pathologic complete response (pCR). Identifying predictive biomarkers of response would therefore be useful. We assessed whether chromosomal copy number alterations (CNAs) can assist in predicting pCR. Pretreatment tumor biopsies and paired normal surgical tissues from the proximal resection margin were collected from 95 rectal cancer patients treated with preoperative CRT and total mesorectal excision in a prospective Phase II study. Tumor and control DNA were extracted, and oligonucleotide array-based comparative genomic hybridization (aCGH) was used to identify CNAs, which were correlated with pCR. Ingenuity pathway analysis (IPA) was then used to identify functionally relevant genes in aberrant regions. Finally, a predictive model for pCR was built using support vector machine (SVM), and leave-one-out cross validation assessed the accuracy of aCGH. Chromosomal regions most commonly affected by gains were 20q11.21-q13.33, 13q11.32-23, 7p22.3-p22.2, and 8q23.3-q24.3, and losses were present at 18q11.32-q23, 17p13.3-q11.1, 10q23.1, and 4q32.1-q32.3. The 25 (26%) patients who achieved a pCR had significantly fewer high copy gains overall than non-pCR patients (P = 0.01). Loss of chromosomal region 15q11.1-q26.3 was significantly associated with non-pCR (P < 0.00002; Q-bound < 0.0391), while loss of 12p13.31 was significantly associated with pCR (P < 0.0003; Q-bound < 0.097). IPA identified eight genes in the imbalanced chromosomal regions that associated with tumor response. SVM identified 58 probes that predict pCR with 76% sensitivity, 97% specificity, and positive and negative predictive values of 91% and 92%. Our data indicate that chromosomal CNAs can help identify rectal cancer patients more likely to develop a pCR to CRT.

The Prognostic Impact of p53 Expression on Sporadic Colorectal Cancer Is Dependent on p21 Status

The prognostic value of p53 and p21 expression in colorectal cancer is still under debate. We hypothesize that the prognostic impact of p53 expression is dependent on p21 status. The expression of p53 and p21 was immunohistochemically investigated in a prospective cohort of 116 patients with UICC stage II and III sporadic colorectal cancer. The results were correlated with overall and recurrence-free survival. The mean observation period was 51.8 ± 2.5 months. Expression of p53 was observed in 72 tumors (63%). Overall survival was significantly better in patients with p53-positive carcinomas than in those without p53 expression (p = 0.048). No differences were found in recurrence-free survival (p = 0.161). The p53+/p21− combination was seen in 68% (n = 49), the p53+/p21+ combination in 32% (n = 23). Patients with p53+/p21− carcinomas had significantly better overall and recurrence-free survival than those with p53+/p21+ (p < 0.0001 resp. p = 0.003). Our data suggest that the prognostic impact of p53 expression on sporadic colorectal cancer is dependent on p21 status.

The prognostic value of c-Kit, K-ras codon 12, and p53 codon 72 mutations in Egyptian patients with stage II colorectal cancer

BACKGROUND

The prognosis for patients with colorectal cancer (CRC) depends mainly on standard clinicopathologic factors. However, patients with similar disease characteristics exhibit various outcomes, especially in stage II. Therefore, the identification of molecular prognostic markers is needed to predict patient outcomes.

METHODS

The authors assessed the prognostic value of c-Kit (also called cluster of differentiation 117 [CD117] or KIT), cyclooxygenase-2 (COX-2), tumor protein 53 (p53), and Kirsten rat sarcoma viral oncogene homolog (K-ras) aberrations in 90 patients with stage II CRC using immunohistochemistry and molecular techniques. The results were correlated with standard clinicopathologic prognostic factors, overall survival (OS), and disease-free survival (DFS).

RESULTS

COX2 and c-Kit overexpression was detected in 54.6% and 59.3% of patients, respectively. Overexpression of p53 was detected in 47 patients, including 29 who had mutations, and a unique mutation pattern was detected with 3 hotspots at codons 72, 245, and 273. Overexpression of ras was detected in 44 patients, including 37 who had mutations. On multivariate analysis, c-Kit overexpression, p53 codon 72 mutations, perforation, and performance status were independent prognostic factors for DFS (P=.054, P=.015, P<.0001, and P=.043, respectively); whereas codon 12 K-ras mutation, performance status, and perforation were independent prognostic factors for OS (P=.033, P=.006, and P<.0001, respectively).

CONCLUSIONS

The current results provide evidence for the prognostic value of c-Kit overexpression in patients with stage II CRC. The high p53 mutation rate and the unique hotspot in codon 72 have not been reported previously in CRC. This may be related to environmental or racial features that are unique to the studied population.

TP53 Arg72Pro polymorphism and colorectal cancer risk: a systematic review and meta-analysis

BACKGROUND

The TP53 rs1042522 polymorphism (c.215C>G, Arg72Pro) has been extensively investigated as a potential risk factor for colorectal cancer, but the results have thus far been inconclusive.

METHODS

We searched multiple electronic databases to identify studies investigating the association between the Arg72Pro polymorphism and colorectal cancer. Individual study odds ratios (OR) and their confidence intervals were estimated using allele-frequency, recessive, and dominant genetic models. Summary ORs where estimated using random effects models.

RESULTS

We identified 23 eligible case-control studies, investigating 6,514 cases and 9,334 controls. There was significant between-study heterogeneity for all genetic models. The control group in one of the studies was not in Hardy-Weinberg equilibrium; only three studies reported that genotyping was blinded to case/control status and five studies used tumor tissue for case genotyping. Overall, we did not identify any association between rs1042522 and colorectal cancer risk under an allele-frequency comparison (OR, 0.99; 95% confidence interval, 0.89-1.09). Likewise, no association was evident under dominant or recessive models. Studies using tumor tissue for case genotyping found a protective effect for the Pro allele, compared with studies using somatic DNA (P(interaction) = 0.03). Results were also inconsistent between different genotyping methods (P(interaction) = 0.03).

CONCLUSION

We did not identify an association between TP53 rs1042522 and colorectal cancer. Published results seem to be driven by technical artifacts rather than true biological effects.

IMPACT

Future genetic association studies should use more rigorous genotyping methods and avoid the use of tumor tissue as a source of DNA to prevent genotype misclassification due to loss of heterozygosity.

Comparison of 17,641 patients with right- and left-sided colon cancer: differences in epidemiology, perioperative course, histology, and survival

PURPOSE

There is a growing amount of data suggesting that carcinomas of the right and left colon should be considered as different tumor entities. Using the data and analysis compiled in the German multicentered study "Colon/Rectum Cancer," we aimed to clarify whether the existing differences influence clinical and histological parameters, the perioperative course, and the survival of patients with right- vs left-sided colon cancer.

METHODS

During a 3-year period data on all patients with colon cancer were evaluated. Right- and left-sided cancers were compared regarding the following parameters: demographic factors, comorbidities, and histology. For patients who underwent elective surgery with curative intent, the perioperative course and survival were also analyzed.

RESULTS

A total of 17,641 patients with colon carcinomas were included; 12,719 underwent curative surgery. Patients with right-sided colon cancer were significantly older, and predominantly women with a higher rate of comorbidities. Mortality was significantly higher for this group. Final pathology revealed a higher percentage of poorly differentiated and locally advanced tumors. Rate of synchronous distant metastases was comparable. However, hepatic and pulmonary metastases were more frequently found in left-sided, peritoneal carcinomatosis in right-sided carcinomas. Survival was significantly worse in patients with right-sided carcinomas on an adjusted multivariate model (odds ratio, 1.12).

CONCLUSIONS

We found that right- and left-sided colon cancers are significantly different regarding epidemiological, clinical, and histological parameters. Patients with right-sided colon cancers have a worse prognosis. These discrepancies may be caused by genetic differences that account for distinct carcinogenesis and biological behavior. The impact of these findings on screening and therapy remains to be defined.

Simultaneous Detection of Colorectal Cancer Mutations in Stool Samples with Biochip Arrays

Colorectal cancer (CRC) is the second main cause of cancer-related death in the Western world and like many other tumours is curable if detected at an early stage. Current detection options include faecal occult blood testing and invasive direct visualisation techniques such as flexible sigmoidoscopy, colonoscopy and barium enema. The availability of a more simple, non-invasive test that detects tumour specific products with optimal analytical performance might overcome barriers among patients who are not willing to undergo more sensitive but invasive tests. One such emerging technology, which has shown promise in recent years, is the analysis of DNA alterations exfoliated from tumour cells into stool. Here we report an analytical platform for non-invasive detection of 28 common mutations within CRC-related genesAPC, TP53, K-rasandBRAFin stool samples based on biochip array technology and applied to the semi-automated Evidence Investigator analyser. Mutation detection was possible in 1000-fold excess of wildtype DNA and analysis of 10 CRC-positive patient samples showed presence of targeted mutations with equivalent mutations also identified by an alternative method. This application represents an excellent tool for the multiplex detection of CRC-specific mutations using a single platform.

Molecular gate keepers succumb to gene aberrations in colorectal cancer in Kashmiri population, revealing a high incidence area

BACKGROUND/AIM

Colorectal cancer (CRC) is one of the leading malignancies worldwide and has been reported to show geographical variation in its incidence, even within areas of ethnic homogeneity. The aim of this study was to identify p53 and K-ras gene mutations in CRC patients in a Kashmiri population, and to assess whether these mutations are linked with clinicopathological parameters.

MATERIALS AND METHODS

Paired tumor and normal tissue samples from a consecutive series of 53 patients undergoing resective surgery for CRC were prospectively studied for p53 and K-ras gene mutations by PCR/single strand conformation polymorphism (SSCP).

RESULTS

Less than half (45%, 19/42) of the patients presented mutations in the p53 gene. Twenty eight mutations were found in the p53 gene, which comprised of 23 substitutions (17 transitions + 6 transversions), and five insertions. The 23 substitutions constituted 18 missense mutations, two nonsense mutations, and three silent mutations. Of the 28 mutations (7.14%) observed in this study, 2 were not previously reported for CRC samples and were identified as novel p53 mutations. A few patients (22.64%, 12/53) presented with mutations in K-ras, constituting 13 missense mutations, out of which 11 were G-->A transitions, one was a G-->C transversion, and one a G-->T transversion. More than half (61.5%) of the mutations occurred in codon 12 whereas a few (38.5%) occurred in codon 13. One tumor contained missense mutations in both codons. Comparison of the mutation profiles of our patients with those of other ethnic populations and regions reflected both differences and similarities, indicating co-exposure to a unique set of risk factors.

CONCLUSION

Mutations of the p53 and K-ras genes are some of the most common genetic changes in the development of human CRC. The high frequency of p53 gene mutations implicates p53 as a predominant factor for CRC in the high-risk ethnic Kashmiri population.

Association between p53 expression and Bcl-2, P-glycoprotein, topoisomerase II alpha, thymidylate synthase and thymidine phosphorylase as potential therapeutic targets in colorectal cancer patients

We evaluated the expression of molecular markers in colorectal adenocarcinoma in relation to p53 protein expression. Tissue samples of 54 patients with colorectal adenocarcinoma were obtained at surgery at university hospitals in the years 2000-2003. These were analyzed by immunohistochemical techniques using primary antibodies for p53, Bcl-2, P-gp, topoisomerase II alpha and Thymidylate Synthase (TS), thymidine phosphorylase/PD- ECGF (TP) and LSAB detection kit. The highest prevalence of expression among six analyzed markers were P-gp and p53 with 77% expression and the lowest one was Topo II with 35% expression. No clinicopathological significance was recorded in colorectal cancer patients. Several immunophenotypes were observed between p53 and other molecular markers. Additionally the prevalence of lack of expression of Bcl-2, Topo II and TS was higher in p53+ tumors than in p53-tumors. A significant association (p = 0.021) existed between p53/Bcl-2 coexpression and mean age of patients (63.5 [10.1]y vs. 52.3 [15.2] y) and between p53/TP coexpression and sex (66.7% male; (p = 0.022). Overexpression of mutated p53 seen in tumor samples may alter the expression pattern of other molecular markers that are predictors of tumor response to chemotherapy regimens. Age and sex of patients could also affect the p53 related proteins such as Bcl-2 and TP, which can affect therapeutic outcome and disease prognosis. These findings emphasize the importance of tumor immunophenotypes as valuable prognostic or predictive markers in clinical settings.

Oncogenetic tree model of somatic mutations and DNA methylation in colon tumors

Our understanding of somatic alterations in colon cancer has evolved from a concept of a series of events taking place in a single sequence to a recognition of multiple pathways. An oncogenetic tree is a model intended to describe the pathways and sequence of somatic alterations in carcinogenesis without assuming that tumors will fall in mutually exclusive categories. We applied this model to data on colon tumor somatic alterations. An oncogenetic tree model was built using data on mutations of TP53, KRAS2, APC, and BRAF genes, methylation at CpG sites of MLH1 and TP16 genes, methylation in tumor (MINT) markers, and microsatellite instability (MSI) for 971 colon tumors from a population-based series. Oncogenetic tree analysis resulted in a reproducible tree with three branches. The model represents methylation of MINT markers as initiating a branch and predisposing to MSI, methylation of MHL1 and TP16, and BRAF mutation. APC mutation is the first alteration in an independent branch and is followed by TP53 mutation. KRAS2 mutation was placed a third independent branch, implying that it neither depends on, nor predisposes to, the other alterations. Individual tumors were observed to have alteration patterns representing every combination of one, two, or all three branches. The oncogenetic tree model assumptions are appropriate for the observed heterogeneity of colon tumors, and the model produces a useful visual schematic of the sequence of events in pathways of colon carcinogenesis.

Distinct pattern of mutations of conserved regions of TP53 in colorectal cancer patients in the Kashmir population: an emerging high-risk area

Background:

Colorectal cancer (CRC) is one of the leading causes of mortality and morbidity. The Kashmir valley, in Northern India, has been described as a high-risk area for colorectal cancer.

Aim:

The aim was to make a preliminary attempt to study mutations in exons 5–8 (the DNA binding domain) of the tumour suppressor gene TP53 in 42 CRC patients from Kashmir.

Materials and methods:

The study population consisted of 42 patients diagnosed with colorectal cancer. Mutations in exons 5–8 of the TP53 gene were detected by means of single-strand conformation polymorphism (SSCP). All samples that showed different band migration patterns in the SSCP were confirmed by sequencing.

Results:

The 28 mutations were found in the TP53 gene in 19 patients, comprised 23 substitutions (17 transitions + six transversions), and five insertions. The 23 substitutions represent 18 missense mutations, leading to amino acid substitutions, two nonsense mutations, leading to stop codons, while the remaining three were silent mutations. The five insertions represented frameshifts. Two of 28 mutations (7.14%) have not been previously reported in colon cancer samples and were identified as novel TP53 mutations. Comparison of the mutation profile with other ethnic populations and regions reflected both differences and similarities indicating co-exposure to a unique set of risk factors.

Conclusions:

Mutation of the TP53 gene is one of the commonest genetic changes in the development of human colorectal cancer. The high frequency of TP53 gene mutations implicates TP53 as a predominant factor for colorectal cancer in the high-risk ethnic Kashmir population.

Combined chemotherapy of hydroxycampothecin with oxaliplatin as an adjuvant treatment for human colorectal cancer

Colorectal cancer (CRC) is a major cause of morbidity and mortality for cancer worldwide, but many patients with CRC are resistant to chemotherapy. We therefore investigated the therapeutic mechanism and clinical effect of combined chemotherapy of hydroxycampothecin (HCPT) with oxaliplatin (L-OHP) on CRC. HCPT represents a potential antitumor agent of Chinese herb. Mice carrying the xenografted human LS174T CRC cells were injected into peritoneal cavities with different drugs: HCPT + L-OHP (OH), HCPT, L-OHP, or saline. Treatment of mice with OH caused the decrease in the volume of tumor and the expression of p53, but increased the apoptotic rate and Fas-L expression, compared to those of animals treated with HCPT or L-OHP, or control animals. Thus, the combination of HCPT with L-OHP could more effectively induce the apoptosis of CRC cells. Furthermore, 56 patients with CRC were treated with HCPT and L-OHP (28 cases, OH group) or L-OHP plus leucovorin plus 5-fluorouracil (28 cases, OFL group), then reviewed the response rate, survival rate and toxicity. The one-year survival rate was 35.07% in OH group and 24.21% in OFL group. However, the occurrence of anemia (51.8%) or diarrhea (60.7%) was higher in OH group than that of 19.6% or 46.4% in OFL group. The clinical results suggest that HCPT plus L-OHP combined chemotherapy could increase the survival time of patients. Taken together, the present study indicates that the combined chemotherapy of HCPT with L-OHP could become a new adjuvant treatment for CRC.

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.