Shinsaku Kanazawa

Genetic Instability Caused by Loss of MutS Homologue 3 in Human Colorectal Cancer

Microsatellite instability (MSI) is a hallmark of mismatch repair (MMR) deficiency. High levels of MSI at mononucleotide and dinucleotide repeats in colorectal cancer (CRC) are attributed to inactivation of the MMR genes, hMLH1 and hMSH2. CRC with low levels of MSI (MSI-L) exists; however, its molecular basis is unclear. There is another type of MSI--elevated microsatellite alterations at selected tetranucleotide repeats (EMAST)--where loci containing [AAAG](n) or [ATAG](n) repeats are unstable. EMAST is frequent in non-CRCs; however, the incidence of EMAST and its cause in CRC is not known. Here, we report that MutS homologue 3 (MSH3) knockdown or MSH3-deficient cells exhibit the EMAST phenotype and low levels of mutations at dinucleotide repeats. About 60% of 117 sporadic CRC cases exhibit EMAST. All of the cases defined as MSI-H (16 cases) exhibited high levels of EMAST. Among 101 non-MSI-H cases, all 19 cases of MSI-L and 35 of 82 cases of MSS exhibited EMAST. Although non-MSI-H CRC tissues contained MSH3-negative tumor cells ranging from 2% to 50% of the total tumor cell population, the tissues exhibiting EMAST contained more MSH3-negative cells (average, 31.5%) than did the tissues not exhibiting EMAST (8.4%). Taken together, our results support the concept that MSH3 deficiency causes EMAST or EMAST with low levels of MSI at loci with dinucleotide repeats in CRC.

Liver Metastasis of a Triple-Negative Breast Cancer and Complete Remission for 5 Years After Treatment With Combined Bevacizumab/Paclitaxel/Carboplatin: Case Report and Review of the Literature

Abstract Triple-negative breast cancer (TNBC) is aggressive, with high risk of visceral metastasis and death. A substantial proportion of patients with TNBC is associated with BRCA mutations, implying that these tumors are sensitive to DNA-damaging agents. We report successful treatment of a metastatic TNBC in a woman with a BRCA2 germline mutation using combined bevacizumab/paclitaxel/carboplatin (BPC) therapy. The patient was pregnant and had liver metastases, and a complete clinical response was sustained for approximately 5 years. Mastectomy was performed during the 29th week of pregnancy, and the baby was later delivered by caesarean section. Subsequently, multiple metastases in both liver lobes were detected using computed tomography and magnetic resonance imaging and the patient was treated with a BPC regimen, which led to complete disappearance of metastatic lesions in the liver. No additional treatment was provided, and after 5 years the patient consented to direct sequencing of BRCA2 and a 6781delG mutation was identified. At the most recent (5-year) follow-up, the patient was alive with good quality of life and no evidence of metastases. This finding suggests that BPC therapy might be considered a good therapeutic option for the treatment of metastatic TNBC in a woman with a BRCA2 germline mutation.

Metastatic nonpalpable invasive lobular breast carcinoma presenting as rectal stenosis: a case report

IntroductionInvasive lobular carcinomas have an increased propensity for distant metastases, particularly to the peritoneum, ovaries, and uterus. In contrast, distant metastases of nonpalpable lobular carcinomas are extremely rare, and the causes of underlying symptoms of primary carcinomas remain unclear. We report a case of an asymptomatic invasive lobular carcinoma with a primary mammary lesion in a patient with rectal stenosis.Case presentationA 69-year-old Japanese woman presented to our hospital for treatment of constipation. Although rectal stenosis was confirmed, thorough testing of her lower digestive tract did not identify its cause. Thus, an exploratory laparotomy and tissue biopsy was performed, and the presence of an invasive lobular carcinoma was confirmed. Subsequent breast examinations showed that the invasive lobular carcinoma that led to the rectal stenosis was a metastatic lesion from a primary lesion of the breast duct. As the present breast lobular carcinoma was asymptomatic and nonpalpable, we did not initially consider metastatic breast cancer as a cause of her symptoms, and the final diagnosis was delayed.ConclusionsPeritoneal metastasis from nonpalpable invasive lobular carcinomas is very rare. However, breast cancer metastasis should be considered when carcinomatous peritonitis is present in a patient with an unknown primary cancer.