Abstract LB-296: Involvement of T-cell immunity in changes in the plasma amino acid profiles of patients with colorectal cancer

Abstract

Abstract Metabolic changes in patients with various disorders, including liver disease and cancer, lead to alterations in amino acid balance, and plasma amino acid profiles can be used to discriminate between non-malnourished patients with cancer and healthy individuals. Not with standing, the mechanisms of amino acid imbalance are not well understood. In patients with cancer, various factors including metabolic changes in the tumor itself and immune responses may affect plasma amino acid levels. To investigate involvement of the immune system, we measured plasma amino acid levels in an orthotopic transplant model of colon cancer established in both conventional BALB/c mice and athymic BALB/c nude mice (T-lymphocyte-deficient mice). CT26 colon cancer cells (murine colon cancer cell line) were implanted into the cecal wall of the BALB/c mice (n=10) and nude mice (n=10). Plasma samples were collected from the tumor-bearing mice at 7 and 14 days after transplantation, and changes in plasma amino acid profiles were compared. Plasma was also collected from mice that underwent sham operation (control mice, n=10). Plasma amino acid concentrations were measured by LC/MS/MS. The plasma concentrations of several amino acids changed significantly in tumor-bearing mice compared to concentrations in control mice. Although cells from the same line were injected into the cecal wall of BALB/c mice and nude mice, a difference was noted in the change in plasma amino acid levels. Plasma Val, Ile, Leu, and Met levels decreased in BALB/c mice but increased in nude mice. There was no difference in the amino acid profile of CT26 tumor tissues between BALB/c mice and nude mice. We then injected antiCD3-antibody into the peritoneal cavity of tumor-bearing BALB/c mice (n=5) to eliminate T-cell function. We also injected IgG into tumor-bearing BALB/c mice (n=5) for control. The pattern of change in amino-acid profiles differed between the two groups of mice. Our findings suggest that T-lymphocyte-mediated immunoreactions are involved in changes in the plasma amino acid profile in patients with colorectal cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-296. doi:10.1158/1538-7445.AM2011-LB-296