The association between ERK inhibitor sensitivity and molecular characteristics in colorectal cancer.

The mitogen-activated protein kinase (MAPK) pathway plays an important role in the colorectal cancer (CRC) progression, being supposed to be activated by the gene mutations, such as BRAF or KRAS. Although the inhibitors of extracellular signal-regulated kinase (ERK) have demonstrated efficacy in the cells with the BRAF or KRAS mutations, a clinical response is not always associated with the molecular signature. The patient-derived organoids (PDO) have emerged as a powerful in vitro model system to study cancer, and it has been widely applied for the drug screening. The present study aims to analyze the association between the molecular characteristics which analyzed by next-generation sequencing (NGS) and sensitivity to the ERK inhibitor (i.e., SCH772984) in PDO derived from CRC specimens. A drug sensitivity test for the SCH772984 was conducted using 14 CRC cell lines, and the results demonstrated that the sensitivity was in agreement with the BRAF mutation, but was not completely consistent with the KRAS status. In the drug sensitivity test for PDO, 6 out of 7 cases with either BRAF or KRAS mutations showed sensitivity to the SCH772984, while 5 out of 6 cases of both BRAF and KRAS wild-types were resistant. The results of this study suggested that the molecular status of the clinical specimens are likely to represent the sensitivity in the PDOs but is not necessarily absolutely overlapping. PDO might be able to complement the limitations of the gene panel and have the potential to provide a novel precision medicine.

[A Case of Radically Resected Sigmoid Colon Cancer with Bladder Invasion after Chemotherapy and Weight Loss in an Extremely Obese Patient].

A 30's extremely obese patient(body mass index: BMI 45 kg/m2)was referred to our hospital with a chief complaint of bloody urine and stool. Colonoscopy revealed a sigmoid colon tumor. Barium enema examination revealed stenosis of the sigmoid colon. CT scan showed a tumor in the sigmoid colon, with bladder invasion. The para-aortic lymph node was partially swollen. We considered surgery to be high risk because of the patient's severe obesity. Therefore, we decided to examine the possibility of radical surgery followed by chemotherapy(mFOLFOX6/cetuximab)with weight reduction. Following this, the tumor had shrunk remarkably, and the patient's BMI decreased from 45 kg/m2 to 39 kg/m2. The visceral fat area was reduced from 298 cm2 to 199 cm2 at the umbilical level. We then performed a sigmoid colectomy with partial resection of the bladder. Thus, chemotherapy combined with weight loss enabled us to perform radical surgery safely for a locally advanced sigmoid colon cancer in a patient with severe obesity.

[A Case of Solitary Residual Lateral Pelvic Lymph Node Metastasis Despite Complete Response of Primary Rectal Cancer Followed by Neoadjuvant Chemoradiotherapy].

A 45-year-old woman was referred to our hospital complaining of diarrhea. Colonoscopy showed a rectal tumor. Histological examination showed moderately differentiated adenocarcinoma. A CT scan revealed a tumor extending from the lower rectum to the anal canal with a lateral pelvic lymph node(LPLN)swelling. We administered neoadjuvant chemoradiotherapy (45 Gy/25 Fr, S-1 80mg/m / 2/day)and the tumor and LPLN shrank remarkably, with a clinically complete response by CT and PET-CT. We then performed abdominoperineal resection with D3 lymph node and bilateral LPLN dissection. Pathological examination revealed complete disappearance of the cancer cells in the primary site, while lymph node metastasis was detected in one LPLN. We report here a rare case in which LPLN metastasis remained despite the pathological complete response of the primary tumor.