Purpose: The aim of our study was to assess whether the polymorphism of the nucleotide excision repair enzyme, excision repair cross-complementing rodent repair deficiency, complementation group 1 (ERCC1), had an effect on the tumor response in patients treated with standard chemotherapy regimens for a metastatic colorectal cancer. We have studied the synonymous polymorphism that causes a single nucleotide change C toTat codon 118 converting a codon of common usage (AAC) to a less used codon (AAT), both coding asparagine. This change results in a decreased ERCC1 gene expression, which impairs repair activity. Experimental Design: Ninety-one patients with a median age of 55.1 years treated for a metastatic colorectal cancer were included in our retrospective study. The ERCC1 polymorphism was analyzed in the normal tissue of all patients. Results: Twenty (22%) were homozygous for AAC codon (C/C genotype), 30 were (33%) homozygous for AAT codon (T/T genotype), and 41 (45%) were heterozygous (C/T genotype). The objective response rate to oxaliplatin in combination with 5-fluorouracil (5-FU) was significantly higher in the T/T genotype group compared with the C/T and the C/C genotype groups (61.9%, 42.3%, and 21.4%, respectively; P = 0.018). By contrast, no significant difference was observed when patients were treated with either 5-FU alone (45%, 29.2%, and 33.3%, respectively; P = 0.407) or in combination with irinotecan (46.1%, 25.0%, and 27.3%, respectively; P = 0.305). Conclusions: Our observations allowed us to define the first useful predictive criterion for oxaliplatin/5-FU response in patients with metastatic colorectal cancer.

Accumulation of frameshift mutations at genes containing coding mononucleotide repeats is thought to be the major molecular mechanism by which mismatch repair-deficient cells accumulate functional alterations. These mutations resulting from microsatellite instability (MSI) can affect genes involved in pathways with a putative oncogenic role, but may also arise in genes without any expected role in MSI carcinogenesis because of the high mutation background of these tumours. We here screened 39 MSI colorectal tumours for the presence of mutations in 25 genes involved in DNA damage signalling and repair pathways. Using a maximum likelihood statistical method, these genes were divided into two different groups that differed significantly in their mutation frequencies, and likely represent mutations that do or do not provide selective pressure during MSI tumour progression. Interestingly, the so-called real-target mutational events were found to be distributed among genes involved in different functional pathways of the DNA metabolism, for example, DNA damage signalling (DNA-PKcs, ATR), double-strand break (DSB) repair (DNA-PKcs, RAD50), mismatch repair (MSH3, MSH6, MBD4) and replication (POLD3). In particular, mutations in MRE11 and/or RAD50 were observed in the vast majority of the tumours and resulted in the concomitant loss of immunohistochemical expression of both proteins. These data might explain why MSI colorectal cancers (CRC) behave differently in response to a wide variety of chemotherapeutic agents, notably those targeting DNA. More generally, they give further insights into how MSI leads to functional changes with synergistic effects in oncogenic pathways.

Complete PT does not modify TIPS' long-term outcome. Rather than a contraindication, PT should be considered as an indication for TIPS in cirrhotic patients with accessible intrahepatic portal vein. Further randomized studies should be planned in cirrhotic patients with recent PT to better qualify TIPS and anticoagulation indications, respectively.

Half of colorectal tumors with microsatellite instability contain frameshift mutations in the (G)8 tract of bax, a major apoptosis effector, but their functional significance remains unclear. We studied the role of bax mutations on bax expression and apoptosis in 59 primary colorectal cancers of which 41 were microsatellite unstable. Tumors were screened for bax(G)8 mutations and evaluated immunohistochemically for bax, bcl-2, and p53 protein expression and apoptotic (M30 cytoDEATH) and proliferative (Ki-67) indexes. We identified bax(G)8 mutations in 20 (49%) of 41 unstable tumors; the mutations were associated significantly with proximal, poorly differentiated, or mucinous adenocarcinomas. Most bax-mutated cases displayed a bax-immunonegative zone in all or part of the tumor that was proved to correspond to biallelic bax(G)8 mutations by microdissection and to confer growth advantage to the tumor by decreasing apoptosis compared with adjacent bax-immunopositive tumor. Biallelic bax(G)8 mutations are subject to positive selection pressure and might disable apoptosis in colorectal cancer.

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