Incidence of germline variants in Lynch syndrome-related genes among Japanese endometrial cancer patients aged 40 years or younger.

[Objective] Lynch syndrome (LS) is an autosomal dominant inherited disorder caused by a germline pathogenic variant in DNA mismatch repair (MMR) genes. Endometrial cancer frequently precedes another LS-associated tumor. This study aimed to clarify the incidence and features of LS in young Japanese endometrial cancer patients.[Methods] Sixty-five patients aged 40 years or younger, who were diagnosed with endometrial cancer, were enrolled in this study. Targeted sequencing of a hereditary colorectal cancer-related gene panel including the MMR genes MLH1, MSH2, MSH6, and PMS2 was conducted on DNA samples extracted from blood cells.[Results] Overall, 6 missense variants (2 in MSH2, 2 in MSH6, and 2 in PMS2), 1 inframe deletion variant in MSH2, 1 splice variant in MSH2, and 1 two-base substitution in the 3' untranslated region in MLH1 were detected in 9 (13.8%) patients. Among these, the splice variant c.1276G > T (p.Ile411_Gly426del16) in MSH2 was annotated as pathogenic, while other variants were of uncertain significance. The patient with the pathogenic variant had a family history of endometrial and colorectal cancer and was diagnosed with endometrial cancer at age 35.[Conclusion] The incidence of LS among Japanese endometrial cancer patients of reproductive age (≤ 40 years) in this study was at least 1.5%; however, 12.3% of patients had variants of uncertain significance in MMR genes.

The single-base-pair deletion, MSH2 c.2635-3delC affecting intron 15 splicing can be a cause of Lynch syndrome.

The proband was a 62-year-old man with ureter cancer. He had a history of metachronous colorectal and gastric cancer. Immunohistochemical staining showed the absence of both MSH2 and MSH6 proteins in the ureter cancer and other available cancer tissue specimens. Genetic testing was conducted to identify the causative genes of hereditary gastrointestinal cancer syndromes including mismatch repair genes. We detected a germline variant, c.2635-3delC, within the splice acceptor site of exon 16, in the MSH2 gene. To investigate whether this variant affected splicing of the gene, RNA sequencing was performed using blood samples. We observed a substantial amount of the transcripts that lacked proper splicing of intron 15 in the indexed case, whereas, a very low amount of such aberrant transcripts was detected in the controls, strongly indicating an association between the variant and splicing defect. These results indicate that MSH2 c.2635-3delC affects normal splicing and might be a cause of Lynch syndrome.

Routine genetic testing of lung cancer specimens derived from surgery, bronchoscopy and fluid aspiration by next generation sequencing.

After the development of EGFR tyrosine kinase inhibitors (TKIs), genetic testing of EGFR became required for effective treatment of lung cancer. Initially, the testing was conducted separately for each mutated region. However, many EGFR mutations have since been identified that determine the efficacy of EGFR-TKIs. Therefore, genetic testing of EGFR by next generation sequencing (NGS) may be a suitable strategy for lung cancer. Here we examined the applicability of the NGS method in regard to sensitivity, time and cost. A total of 939 specimens were obtained from 686 lung cancer patients at our hospital. DNA and RNA were simultaneously extracted from specimens derived from surgery, bronchoscopy, and fluid aspiration. Specimens included cerebrospinal fluid, pleural effusion, abdominal fluid, and pericardial effusion. From RNA, target regions (EGFR, KRAS, ALK fusion and RET fusion) were enriched by RT-PCR and sequenced with MiSeq. From DNA, PCR or PCR-RFLP conventional methods were performed. NGS and conventional methods were carried out routinely per week. Among the total 939 specimens, 38 specimens could not be examined with NGS. Among these, 34 specimens were analyzed by conventional testing with simultaneously extracted DNA. The remaining four specimens could not be tested with either method. Compared with the conventional method, the concordance rate of mutations was 99% (892/901), excluding specimens with NGS failure. The time period required from processing of specimens to results was 4 days, and the cost per sample was sufficiently low. In conclusion, the genetic testing with NGS method was useful for lung cancer treatment. The cost, sensitivity and time were able to tolerate routine examinations.

The silent mutation MLH1 c.543C>T resulting in aberrant splicing can cause Lynch syndrome: a case report.

The proband was a 67-year-old man with transverse and sigmoid colon cancer. Microsatellite instability analysis revealed a high frequency of microsatellite instability, and immunohistochemical staining showed the absence of both MLH1 and PMS2 proteins in the sigmoid colon cancer tissue specimens from the patient. DNA sequencing revealed a nucleotide substitution c.543C>T in MLH1, but this variant did not substitute an amino acid. The MLH1 c.543C>T variant was located 3 bases upstream from the end of exon 6 and created a new splice donor site 4 bases upstream from the end of exon 6. Consequently, the last 4 bases of exon 6 were deleted and frameshift occurred. Thus, the MLH1 c.543C>T silent mutation is considered 'pathogenic'.