Colorectal cancer (CRC) is one of the most common cancers worldwide. Although short-term cultures of tumour sections and xenotransplants have been used to determine drug efficacy, the results frequently fail to confer clinically useful information. Biomarker discovery has changed the paradigm for advanced CRC, though the presence of a biomarker does not necessarily translate into therapeutic success. To improve clinical outcomes, translational models predictive of drug response are needed. We describe a simple method for the fast establishment of CRC patient-derived explant (CRC-PDE) cultures from different carcinogenesis pathways, employing agitation-based platforms. A total of 26 CRC-PDE were established and a subset was evaluated for viability (n = 23), morphology and genetic key alterations (n = 21). CRC-PDE retained partial tumor glandular architecture and microenvironment features were partially lost over 4 weeks of culture. Key proteins (p53 and Mismatch repair) and oncogenic driver mutations of the original tumours were sustained throughout the culture. Drug challenge (n = 5) revealed differential drug response from distinct CRC-PDE cases. These findings suggest an adequate representation of the original tumour and highlight the importance of detailed model characterisation. The preservation of key aspects of the CRC microenvironment and genetics supports CRC-PDE potential applicability in pre- and co-clinical settings, as long as temporal dynamics are considered.

Serrated polyposis syndrome (SPS) is characterized by the development of multiple colorectal serrated polyps and increased predisposition to colorectal cancer (CRC). However, the molecular basis of SPS, especially in cases presenting family history of SPS and/or polyps and/or CRC in first-degree relatives (SPS-FHP/CRC), is still poorly understood. In a previous study, we proposed the existence of two molecular entities amongst SPS-FHP/CRC families, proximal/whole-colon and distal SPS-FHP/CRC, according to the preferential location of lesions and somatic events involved in tumor initiation. In the present study, we aimed to investigate these distinct subgroups of SPS patients in a larger cohort at the germline level and to identify the genetic defects underlying an inherited susceptibility for these two entities. Next-generation sequencing was performed using multigene analysis with a custom-designed panel in a Miseq platform in 60 SPS patients (with and without/unknown FHP/CRC). We found germline pathogenic variants in 6/60 patients (ATM, FANCM, MITF, RAD50, RAD51C, and RNF43). We also found variants of unknown significance (VUS), with prediction of probable damaging effect in 23/60 patients (ATM, BLM, BRCA1, FAN1, ERCC2, ERCC3, FANCA, FANCD2, FANCL, MSH2, MSH6, NTHL1, PALB2, PDGFRA, PMS2, PTCH1, RAD51C, RAD51D, RECQL4, TSC2, WRN, and XRCC5 genes). Most variants were detected in gene coding for proteins of the Fanconi Anemia (FA) pathway involved in the DNA Interstrand-Cross Link repair (ICLR). Notably, variants in ICLR genes were significantly more frequent in the proximal/whole-colon than in the distal subgroup [15/44 (34%) vs 1/16 (6%), p = 0.025], as opposed to the non-ICLR genes that were slightly more frequent in the distal group [8/44 (18%) vs. 5/16 (31%), p > 0.05]. Germline defects in the DNA-ICLR genes may contribute to increased serrated colorectal polyps/carcinoma risk in SPS patients, particularly in proximal/whole-colon SPS. The inclusion of DNA-ICLR genes in the genetic diagnosis of SPS patients, mainly in those with proximal/whole-colon lesions, should be considered and validated by other studies. In addition, patients with germline defects in the DNA-ICLR genes may be more sensitive to treatment with platinum-based therapeutics, which can have implications in the clinical management of these patients.

Recognition of a hereditary colorectal cancer (CRC) syndrome is crucial and Lynch Syndrome (LS) is the most frequent immunohistochemistry (IHC)—screening for mismatch repair proteins (MMR) deficiency in CRC is therefore advocated. An unicentric cohort study was conducted in a central Oncological Hospital to assess its results. All patients under 70 years-old admitted between July 2017–June 2019 and submitted to surgery for CRC were included. Of 275 patients, 56.0% were male, median age 61.0 (IQR:54.5–65.0), with synchronous tumors in six. Histology revealed high grade adenocarcinoma in 8.4%; mucinous and/or signet ring differentiation in 11.3%; and lymphocytic infiltration in 29.8%. Amsterdam (AC) and Bethesda (BC) Criteria were fulfilled in 11 and 74 patients, respectively. IHC revealed loss of expression of MMR proteins in 24 (8.7%), mostly MLH1 and PMS2 (n = 15) and PMS2 (n = 4). Among these, no patients fulfilled AC and 13 fulfilled BC. BRAF mutation or MLH1 promoter hypermethylation was found in four patients with MLH1 loss of expression. Genetic diagnosis was performed in 51 patients, 11 of them with altered IHC. LS was diagnosed in four, and BC was present in three. One patient would not have been diagnosed without routine IHC screening. These results strengthen the important role of IHC screening for MMR proteins loss of expression in CRC.