Inhibitory Effects of Isoflavones on Tumor Growth and Cachexia in Newly Established Cachectic Mouse Models Carrying Human Stomach Cancers

Abstract

Cachexia, a negative prognostic factor, worsens a patient's quality of life. We established 2 novel cachexia models with the human stomach cancer cell line MKN-45, which was subcloned to produce potent cachexia-inducing cells by repeating the xenografts in immune-deficient mice. After subsequent xenografts, we isolated potent cachexia-inducing cells (MKN45cl85 and 85As2mLuc). Xenografts of MKN45cl85 cells in mice led to substantial weight loss and reduced adipose tissue and musculature volumes, whereas xenografts of 85As2mLuc cells resulted in highly metastatic and cachectic mice. Surgical removal of tumor tissues helped the mice regain body-weight in both mouse models. In vitro studies using these cells showed that isoflavones reduced their proliferation, implying that the isoflavones possess antiproliferative effects of these cancer cell lines. Isoflavone treatment on the models induced tumor cytostasis, attenuation of cachexia, and prolonged survival whereas discontinuation of the treatment resulted in progressive tumor growth and weight loss. The inhibitory effects of tumor growth and weight loss by isoflavones were graded as soy isoflavone aglycone AglyMax > daidzein > genistein. These results demonstrated that the 2 novel cachectic mouse models appear useful for analyzing the mechanism of cancer cachexia and monitoring the efficacy of anticachectic agents.

New cancer cachexia rat model generated by implantation of a peritoneal dissemination-derived human stomach cancer cell line

“…However, young rats (aged 8 wk at the time of implantation) were used; therefore, senescence, which is common in human cancer, may have been a limitation of the study. Although 85As2 cell implantation can cause peritoneal dissemination accompanied by ascites (63), the decreased food intake in our model was not associated with either condition. Reduced FFM in cachectic rats was thought to be caused primarily by wasting skeletal muscle and organ tissues, as evidenced by the reduction in all measured musculature weights, muscle atrophy (e.g., gastrocnemius muscle), and reduced spleen and liver weights.…”

“…MKN45cl85 and 85As2 cell lines were established from the human stomach MKN-45 cancer cell line, as described previously (63). Cells were maintained in RPMI 1640 medium (Nacalai Tesque, Kyoto, Japan) supplemented with 10% fetal bovine serum (Invitrogen, Carlsbad, CA), 100 IU/ml penicillin G sodium, and 100 g/ml streptomycin sulfate (Nacalai Tesque) under a 5% CO 2 and 95% air atmosphere at 37°C.…”

“…Thus, anorexia is very important for the evaluation of cachexia. In our previous mouse model, evaluation of cachexia based on weight loss was possible, whereas anorexia could not be used to assess cachexia because of instability in the reduction of food consumption (63). There-fore, our mouse cachexia model was not suitable to evaluate drug efficacy or mechanisms of cachexia-associated anorexia.…”

“…Among the cell lines that were screened, only the MKN-45 cell line induced body weight loss, with an incidence of 40% in tumor-bearing mice (63). On the basis of these findings, we established two novel cell lines from MKN-45 cells: MKN45cl85 and 85As2 (63).…”

“…To address the need for an experimental stomach cancer cachexia animal model, we previously screened 15 human stomach cancer cell lines for their ability to induce weight loss in mice after subcutaneous implantation (63). Among the cell lines that were screened, only the MKN-45 cell line induced body weight loss, with an incidence of 40% in tumor-bearing mice (63).…”