BRAF
 p.V600E-specific immunohistochemical assessment in colorectal cancer endoscopy biopsies is consistent with the mutational profiling

Colorectal cancer (CRC) shows aggregation in some families but no alterations in the known hereditary CRC genes. We aimed to identify new candidate genes which are potentially involved in germline predisposition to familial CRC. An integrated analysis of germline and tumor whole-exome sequencing data was performed in 18 unrelated CRC families. Deleterious single nucleotide variants (SNV), short insertions and deletions (indels), copy number variants (CNVs) and loss of heterozygosity (LOH) were assessed as candidates for first germline or second somatic hits. Candidate tumor suppressor genes were selected when alterations were detected in both germline and somatic DNA, fulfilling Knudson’s two-hit hypothesis. Somatic mutational profiling and signature analysis were also performed. A series of germline-somatic variant pairs were detected. In all cases, the first hit was presented as a rare SNV/indel, whereas the second hit was either a different SNV (3 genes) or LOH affecting the same gene (141 genes). BRCA2, BLM, ERCC2, RECQL, REV3L and RIF1 were among the most promising candidate genes for germline CRC predisposition. The identification of new candidate genes involved in familial CRC could be achieved by our integrated analysis. Further functional studies and replication in additional cohorts are required to confirm the selected candidates.

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Microdissection-Based Allelotyping: A Novel Technique to Determine the Temporal Sequence and Biological Aggressiveness of Colorectal Cancer

The American Surgeon ◽

10.1177/000313480607200516 ◽

2006 ◽

Vol 72 (5) ◽

pp. 445-453 ◽

Cited By ~ 1

Author(s):

T. Clark Gamblin ◽

Sydney D. Finkelstein ◽

Neil Upsal ◽

Jonathan D. Kaye ◽

David Blumberg

Keyword(s):

Colorectal Cancer ◽

Primary Tumor ◽

Temporal Sequence ◽

Allelic Loss ◽

Fixed Tissue ◽

Tumor Spread ◽

Primary Tumors ◽

Mutational Change ◽

Mutational Profiling ◽

Metastatic Sites

Pathologic staging in colorectal adenocarcinoma (CA) is based on the concept that the timing of metastatic tumor spread is directly related to the depth of the primary tumor invasion. To evaluate the temporal sequence of CA metastasis, we performed microdissection mutational profiling at multiple microscopic sites of primary and metastatic CA specimens. Twenty-one cases of CA were selected from fixed-tissue archives. Primary tumors were microdissected at the deepest point of invasion. Comparative mutational profiling for different genomic loci [1p36(CCM = cutaneous malignant melanoma], 3p26(OGGI = 8 oxoguanine DNA glycosylase), 5q23 (APC, MCC = mutated in colorectal cancer), 9p21(p16/CDKN2A = cyclin-dependent kinase 2A), 10q23(PTEN = phosphatase and tensin homolog [mutated in multiple advanced cancers 1]), 12p12(K-ras-2 point mutation), 17p13(TP53), 18q25(DCC= deleted in colorectal cancer) was carried out on each microdissected tissue target using microsatellite loss of heterozygosity determination or DNA sequencing. All primary and metastatic sites of CA manifested acquired mutational change in 18 to 91 per cent of the genomic markers. In 15/21 (71%) cases, metastatic sites lacked a specific allelic loss seen in the corresponding primary tumor, indicating that the metastasis occurred before maximal depth of primary invasion. This was further supported by discordant mutational profiles between primary and secondary tumors, requiring divergent clonal evolution. This is the first report describing the temporal sequence and significance of sequential mutational acquisition in clinical tissue specimens with potential implications for a new molecular pathology approach to classify human cancer.

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