METHOD: Whole-genome sequencing (WGS) was performed in seven early-age-onset Malay CRC patients. Potential germline genetic variants, including single-nucleotide variations and insertions and deletions (indels), were prioritized using functional and predictive algorithms.

RESULTS: An average of 3.2 million single-nucleotide variations (SNVs) and over 800 indels were identified. Three potential candidate variants in three genes-IFNE, PTCH2 and SEMA3D-which were predicted to affect protein function, were identified in three Malay CRC patients. In addition, 19 candidate genes-ANKDD1B, CENPM, CLDN5, MAGEB16, MAP3K14, MOB3C, MS4A12, MUC19, OR2L8, OR51Q1, OR51AR1, PDE4DIP, PKD1L3, PRIM2, PRM3, SEC22B, TPTE, USP29 and ZNF117-harbouring nonsense variants were prioritised. These genes are suggested to play a role in cancer predisposition and to be associated with cancer risk. Pathway enrichment analysis indicated significant enrichment in the olfactory signalling pathway.

MATERIALS AND METHODS: This was a retrospective study of YOCRC (<50 years) over 8 years (January 2013 to December 2021). Immunohistochemistry staining of FOXP3, BRAFV600E, and MMR protein expression was performed using monoclonal antibodies. The staining intensity and percentage of positive cells were used to evaluate the staining using immunoreactive scoring. All data were analysed using descriptive and correlation statistics. A p-value of ≤ 0.05 was taken as statistically significant.

RESULTS: A total of 65 YOCRC patients were diagnosed, out of which 53.8% had proficient MMR (pMMR) with a mean age of 41, while 46.2% had deficient MMR (dMMR) with a mean age of 35.5. The pMMR with the BRAFV600E+ group expressed higher FOXP3+Tregs (54.2%) than the dMMR with the BRAFV600E+ group (22.9%). Patients with lower FOXP3+Tregs were observed more in dMMR with BRAFV600E- (47%) than in pMMR with BRAFV600E- (5.9%). There was a statistically significant association between the density of expressed FOXP3+Tregs with MMR and BRAFV600E status (p=0.002).

Methods: Eighty (40 right-sided and 40 left-sided) formalin-fixed, paraffin-embedded primary CRC were immunohistochemically studied for CD133, a putative CRC stem cell marker, and MMR proteins MLH1, MSH2, MSH6 and PMS2. CD133 expression was semi-quantitated for proportion of tumor immunopositivity on a scale of 0-5 and staining intensity on a scale of 0-3 with a final score (units) being the product of proportion and intensity of tumor staining. The tumor was considered immunopositive only when the tumor demonstrated moderate to strong intensity of CD133 staining (a decision made after analysis of CD133 expression in normal colon). Deficient MMR (dMMR) was interpreted as unequivocal loss of tumor nuclear staining for any MMR protein despite immunoreactivity in the internal positive controls.

Results: CD133 was expressed in 36 (90.0%) left-sided and 28 (70.0%) right-sided tumors (p  0.05).

RESULTS: In the genomic analysis, 33 homozygous and 1377 heterozygous mutations in the coding sequences of the genome of MT strain were detected. Among these heterozygous mutations, the proportion of mutated reads in each gene was different, ranging from 21 to 75%. These results suggest that the MT strain may contain multiple nuclei containing different mutations. We tried to isolate haploid spores from the MT strain to prove its ploidy, but this strain did not sporulate under the conditions tested. Heterozygous mutations detected in genes which are important for sporulation likely contribute to the sporulation deficiency of the MT strain. Homozygous and heterozygous mutations were found in genes encoding enzymes involved in amino acid metabolism, the TCA cycle, purine and pyrimidine nucleotide metabolism and the DNA mismatch repair system. One homozygous mutation in AgILV2 gene encoding acetohydroxyacid synthase, which is also a flavoprotein in mitochondria, was found. Gene ontology (GO) enrichment analysis showed heterozygous mutations in all 22 DNA helicase genes and genes involved in oxidation-reduction process.