Correlation between efficacy of PSK postoperative adjuvant immunochemotherapy for gastric cancer and expression of MHC class I.

Protein-bound polysaccharide K (PSK) is a glycoprotein that is purified from the mushroom Coriolus versicolor. In Japan, PSK is clinically used in combination with anticancer agents following gastric cancer surgery. Evaluation of the response is difficult, as efficacy is determined via antitumor immunoenhancing effects, and for that reason PSK has not become a standard therapy. The present study evaluated the expression of MHC class I in gastric cancer patients who received PSK postoperative adjuvant immunochemotherapy, and investigated the correlation between MHC class I expression and clinical outcomes. The subjects comprised 349 patients with stage II/III gastric cancer, who had received adjuvant therapy following curative resection between 1995 and 2008. MHC class I expression in the primary lesion was evaluated by immunohistochemical staining. Patients were divided into two treatment groups: one was only administered oral chemotherapy (chemotherapy-only group) and the other was administered chemotherapy plus PSK (PSK group). The clinical outcomes were compared between the two groups. The two groups did not differ in regard to their MHC class I expression. Expression-negative cases demonstrated 3-year recurrence-free survival (RFS) rates of 65% in the PSK group and 47% in the chemotherapy-only group. Therefore, the PSK group revealed a prolonged survival. For the 82 expression-negative cases with pN2 or greater, the RFS rates were 68% in the PSK group and 28% in the chemotherapy-only group, representing a significant difference. Thus, PSK adjuvant immunochemotherapy may be effective in MHC class I-negative patients, who are in a state of antitumor immunological tolerance, and patients with advanced lymph node metastasis of pN2 or greater.

[A case of long-term survival after undergoing S-1 based multidisciplinary therapy for liver metastasis of gastric cancer].

We encountered a case of gastric cancer accompanied with liver metastasis, which had a good response to chemotherapy of S-1. A 68-year-old female was admitted to our hospital due to further examination of gastric tumor detected by an outpatient physician. She was found to have a type-3 gastric cancer in upper gastrointestinal endoscopy and a metastatic tumor of the liver in abdominal CT. Although chemotherapy of S-1 was inducted for the lesions, both the primary and liver tumors were dramatically reduced. We subsequently performed total gastrectomy and partial hepatectomy. Abdominal CT scan at 11 months after the initial operation revealed metachronous liver metastasis. She received combination chemotherapy of S-1 and CDDP. After 5 courses of the combination chemotherapy, the liver tumor disappeared. She has survived for 8 years without a recurrence after the initial operation. There was negative findings of immunostaining with thymidylate synthetase (TS), which was target enzyme for 5-FU at a biopsy sample of the primary gastric tumor before chemotherapy of S-1. TS immunostaining may be a useful marker for S-1 combined therapy for gastric cancer associated with liver metastases.

Identification of HLA-A*0201- and A*2402-restricted epitopes of mucin 5AC expressed in advanced pancreatic cancer.

OBJECTIVES: Mucin 5AC (MUC5AC) was previously identified as being expressed in most pancreatic ductal adenocarcinomas. We studied the significance of MUC5AC expression for the development of pancreatic ductal adenocarcinoma and the possibility of using MUC5AC as a target for immunotherapy for pancreatic cancer. METHODS: We immunohistochemicaly tested MUC5AC expression in 134 specimens. To assess the possibility of using the MUC5AC protein to develop an anticancer vaccine, we examined MUC5AC for possible peptide epitopes to elicit cytotoxic T lymphocytes (CTLs). RESULTS: In immunohistochemical analysis, MUC5AC was absent from all cell types of the normal pancreas but was expressed de novo in 79% of invasive ductal adenocarcinoma. Clinicopathologically, primary tumors with lymph node metastasis had a significantly higher expression of MUC5AC. Next, we successfully established CTL clones stimulated by the MUC5AC-A02-1398 (FLNDAGACV) and MUC5AC-A24-716 (TCQPTCRSL) peptides, which have specific cytotoxicity against the corresponding HLA-A*0201- and A*2402-positive target cells pulsed with the candidate peptide. Each CTL clone also demonstrated its cytotoxic activity toward pancreatic cancer cells endogenously expressing MUC5AC. CONCLUSIONS: Our results suggest that MUC5AC is a novel tumor-associated antigen that has potential application as a vaccine against pancreatic cancer.

Anti-protein-bound polysaccharide-K monoclonal antibody binds the active structure and neutralizes direct antitumor action of the compound.

Protein-bound polysaccharide K (PSK) is extracted and purified from Coriolus versicolor (CM101), and is used as an anti-cancer agent. In this study, focusing on the direct actions of PSK, we investigated whether PSK reaches tumor and immune tissues with its active structure remaining intact, and the direct action of PSK was evaluated by its antitumor effects against MethA fibrosarcomas implanted in immunodeficient NOD/SCID mice. The results obtained suggest that PSK reaches the tumor tissue in its active form and exhibits antitumor effects against MethA cells.