DNA content analysis of colorectal cancer defines a distinct 'microsatellite and chromosome stable' group but does not predict response to radiotherapy

Investigating genomic, proteomic, and post-transcriptional regulation profiles in colorectal cancer: a comparative study between primary tumors and associated metastases

INTRODUCTION

Approximately 50% of patients with primary colorectal carcinoma develop liver metastases. This study investigates the possible molecular discrepancies between primary colorectal cancer (pCRC) and their respective metastases.

METHODS

A total of 22 pairs of pCRC and metastases were tested. Mutation profiling of 26 cancer-associated genes was undertaken in 22/22primary-metastasis tumour pairs using next-generation sequencing, whilst the expression of a panel of six microRNAs (miRNAs) was investigated using qPCRin 21/22 pairs and 22 protein biomarkers was tested using Reverse Phase Protein Array (RPPA)in 20/22 patients' tumour pairs.

RESULTS

Among the primary and metastatic tumours the mutation rates for the individual genes are as follows:TP53 (86%), APC (44%), KRAS (36%), PIK3CA (9%), SMAD4 (9%), NRAS (9%) and 4% for FBXW7, BRAF, GNAS and CDH1. The primary-metastasis tumour mutation status was identical in 54/60 (90%) loci. However, there was discordance in heterogeneity status in 40/58 genetic loci (z-score = 6.246, difference = 0.3793, P < 0.0001). Furthermore, there was loss of concordance in miRNA expression status between primary and metastatic tumours, and 57.14-80.95% of the primary-metastases tumour pairs showed altered primary-metastasis relative expression in all the miRNAs tested. Moreover, 16 of 20 (80%) tumour pairs showed alteration in at least 3 of 6 (50%) of the protein biomarker pathways analysed.

CONCLUSION

The molecular alterations of primary colorectal tumours differ significantly from those of their matched metastases. These differences have profound implications for patients' prognoses and response to therapy.

Integrated Decision-Making in the Treatment of Colon-Rectal Cancer: The Case of KRAS-Mutated Tumors

In recent years, precision medicine has taken an increasing place in various branches of medical oncology, including colorectal cancer. Among the potentially relevant mutations for this cancer is the KRAS mutation, initially defined as "untargetable"; today, we see the birth of new molecules that target one of the variants of the KRAS mutation, KRAS G12C, having a significant impact on the therapeutic options for other malignancies, such as metastatic lung cancer. This fundamental step forward has stimulated scientific research on other potential targets of KRAS, both indirect and direct, and combination treatments aiming to overcome the mechanisms of resistance to these drugs that decrease in efficacy in colorectal cancer. What was once a negative predictive marker of response to anti-EGFR drugs today has become a potential target for targeted treatments. In turn, the prognostic role of the mutation has become extremely interesting, making it a potentially useful element in therapeutic decision-making, not only regarding oncological treatments but also in a more complex and complete manner within a global vision of the patient, involving other figures on the multidisciplinary team, such as surgeons, radiotherapists, and interventional radiologists.

Nucleic acid-based markers of response to neoadjuvant chemoradiotherapy in locally advanced rectal cancer

The progress that has been made in the treatment of rectal cancer has mostly resulted from multimodality strategy approach that combines surgery, chemotherapy and radiotherapy. In locally advanced rectal cancer (LARC), surgery remains the primary treatment, while neoadjuvant chemoradiotherapy (nCRT) is used to downsize or downstage the tumor before surgical resection. Highly variable response to nCRT observed in LARC patients raises the need for biomarkers to enable prediction and evaluation of treatment response in a more efficient and timely manner than currently available tools. The search for predictive biomarkers continues beyond blood proteins, which have failed in subsequent validation studies. This review presents nucleic acids-based markers and their predictive potential in LARC patients. Most of the candidate biomarkers come from relatively small single-institution studies. The only candidate biomarker that emerged as relevant in more than a single study was elevated levels of Fusobacterium nucleatum nucleic acids in tumor tissue. Considering that this marker is easily accessible through non-invasive analysis of faecal samples, its predictive potential is worth further validation. The other candidate nucleic acid-based biomarkers require more consistent studies on larger cohorts before they can be considered for use in clinical setting.

PIK3CA mutation and clinicopathological features of colorectal cancer: a systematic review and Meta-Analysis

Background: There is conflicting evidence regarding the association between PIK3CA mutations and clinicopathological features of colorectal cancer (CRC). We performed a comprehensive meta-analysis investigating the association between PIK3CA mutations and clinicopathological features in CRC, including subgroup analysis of mutations in exons 9 and 20, to elucidate the role of PIK3CA mutations in CRC.Materials and Methods: A detailed literature search was performed within the PubMed, Web of Science, and Embase databases, examining the associations between PIK3CA mutations and demographic characteristics, clinicopathologic parameters, and molecular features in patients with CRC. The odds ratios with 95% confidence intervals were used to estimate the effect of PIK3CA mutations on outcome parameters.Results: Forty-four studies enrolling 17621 patients were eligible for inclusion. PIK3CA mutations were associated with proximal tumor location, mucinous differentiation, KRAS mutations, and microsatellite instability (MSI). Subgroup analysis demonstrated that PIK3CA exon 9 mutations were positively associated with proximal tumor location and KRAS mutations, and negatively associated with BRAF mutations and MSI; exon 20 mutations were associated with proximal tumor location, KRAS mutations, BRAF mutations and MSI.Conclusions: Our findings suggest that overall or exon-specific PIK3CA mutations showed null associations with key clinicopathological parameters, including disease stage and tumor differentiation, indicating that PIK3CA mutations do not predict aggressive clinicopathological characteristics in CRC. As PIK3CA mutations were found to be closely associated with KRAS mutations, their relationship warrants further investigation. Since PIK3CA exon 9 and 20 mutations showed different tendencies with regard to BRAF mutation and MSI status, they may have distinct molecular impacts on CRC.

Targeted next generation sequencing reveals a common genetic pathway for colorectal cancers with chromosomal instability and those with microsatellite and chromosome stability

INTRODUCTION

Microsatellite stable sporadic colorectal cancers (CRCs) can be classified as either tumours with chromosomal instability (CIN+) or tumours that are 'Microsatellite and Chromosomal Stable' (MACS). The CIN + tumours are aneuploid whilst MACS are near-diploid; little else is known about their differences. We compared the mutation profiles of CIN + and MACS CRCs.

METHOD

Targeted Next Generation Sequencing for mutation in 26 driver genes (TruSight-26 kit) was undertaken in 46 CIN + and 35 MACSCRCs. Tumours were compared for mutation frequency, allelic imbalance and clonal heterogeneity.

RESULTS

Mutations were detected in 58% genes and, overall, mutation in driver genes was at expected frequencies. Comparison of classes revealed similar mutation frequencies in most genes and allelic imbalance atAPC and TP53. Differences were seen in mutation frequency in KRAS (41% CIN+ vs 68% MACS, p = 0.015) and GNAS (0% CIN+ vs 12% MACS, p = 0.032). Twenty percent CIN + CRCs harboured mutations only in TP53 - a profile not seen in the MACS tumours (p = 0.009). None of the differences were significant after multiple testing corrections.

CONCLUSIONS

The mutation profiles of CIN and MACS CRCs are similar. The events allowing aneuploidy (or forcing retention of diploidy) remain unknown.

N_LyST: a simple and rapid screening test for Lynch syndrome

Aims

We sought to use PCR followed by high-resolution melting analysis to develop a single closed-tube screening panel to screen for Lynch syndrome. This comprises tests for microsatellite instability (MSI), MLH1 methylation promoter and BRAF mutation.

Methods

For MSI testing, five mononucleotide markers (BAT25, BAT26, BCAT25, MYB, EWSR1) were developed. In addition, primers were designed to interrogate Region C of the MLH1 promoter for methylation (using bisulphite-modified DNA) and to test for mutations in codon 600 of BRAF. Two separate cohorts from Nottingham (n=99, 46 with MSI, 53 being microsatellite stable (MSS)) and Edinburgh (n=88, 45 MSI, 43 MSS) were tested.

Results

All the cases (n=187) were blind tested for MSI and all were correctly characterised by our panel. The MLH1 promoter and BRAF were tested only in the Nottingham cohort. Successful blinded analysis was performed on the MLH1 promoter in 97 cases. All MSS cases showed a pattern of non-methylation while 41/44 cases with MSI showed full methylation. The three cases with MSI and a non-methylated pattern had aberrations in MSH2 and MSH6 expression. BRAF mutation was detected in 61% of MSI cases and 11% of MSS cases.

Finally, 12 cases were blind screened by using the whole panel as a single test. Of these, five were identified as MSS, four as MSI/non-LS and three as MSI/possible LS. These results were concordant with the previous data.

Conclusion

We describe the Nottingham Lynch Syndrome Test (N_LyST). This is a quick, simple and cheap method for screening for Lynch syndrome.

Impact of specific KRAS mutation in exon 2 on clinical outcome of chemotherapy- and radiotherapy-treated colorectal adenocarcinoma patients

Background and Objectives

Knowledge obtained via high-throughput technologies, used for tumor genome sequencing or identifying gene expression and methylation signatures, is clinically applicable thanks to molecular characterization in the context of tumor development and progression. This study was conducted to assess the impact of specific KRAS mutation in codons 12 and 13 on clinical outcome of chemotherapy and radiotherapy in colorectal cancer patients.

Methods

A total of 239 samples of colorectal adenocarcinoma underwent histological evaluation and DNA isolation.

Results and Conclusions

Patients with a mutation in KRAS codon 13 experienced worse outcome than those with a mutation in KRAS codon 12. Moreover, the cases of mutations in KRAS codons 12 or 13 were associated with a significantly higher mortality than the cases of wild-type KRAS, and some patients with KRAS mutated in codon 12 had an exceptionally long overall survival. Finally, primary preoperative radiation therapy followed by surgery significantly increased overall survival more efficiently than surgery followed by chemotherapy. This should be investigated in further studies. The fact that all patients treated with radiotherapy + surgery were alive, again focused our attention on the effect of preoperative radiation therapy on the prognosis for colorectal cancer patients. However, the number of patients in this subgroup is too small to allow any specific explanation for this observation. We should, rather, point out a problem for further investigation.