Analysis of Potential Alterations Affecting SETBP1 as a Novel Contributing Mechanism to Inhibit PP2A in Colorectal Cancer Patients.

BACKGROUND: The functional loss of the tumor suppressor protein phosphatase 2A (PP2A) occurs in a wide variety of human cancers including colorectal cancer (CRC), and SET overexpression has been reported as a key contributing mechanism to inhibit PP2A. Although SET binding protein 1 (SETBP1) overexpression and gain of function mutations have been described in several hematological malignancies as common events that increase the expression levels of the PP2A inhibitor SET, thereby leading to PP2A inactivation, the potential existence of SETBP1 alterations in CRC still remains unexplored. METHODS: We studied the expression profile of SETBP1 by Western blot in a set of CRC cell lines and patient samples. Moreover, we performed co-immunoprecipitation assays to analyze the formation of the previously reported SETBP1-SET-PP2A inhibitory complex. Furthermore, we evaluated the mutational status of SETBP1 by pyrosequencing assays in a cohort of 55 CRC patients with metastatic disease after the immunohistochemical characterization of SET and p-PP2A expression in this cohort. RESULTS: We found high SETBP1 expression in several CRC lines but only in two of the patients analyzed. In addition, we demonstrated the formation of the SETBP1-SET-PP2A heterotrimeric complex in CRC cells. However, we failed to detect SETBP1 mutations in any of the CRC patient samples included in the study. CONCLUSIONS: Our results suggest that SETBP1 expression is mainly similar o lower in colorectal cancer tissue compared to normal colonic mucosa. However, its overexpression is a low prevalent alteration which could contribute to inhibit PP2A in CRC through the formation of a SETBP1-SET-PP2A complex in some CRC patients. Moreover, SETBP1 mutations are, if exist, rare events in CRC patients.

A multifactorial anti-cachectic approach for cancer cachexia in a rat model undergoing chemotherapy.

BACKGROUND: The effectiveness of drugs aimed at counteracting cancer cachexia is generally tested in pre-clinical rodent models, where only the tumour-induced alterations are taken into account, excluding the co-presence of anti-tumour molecules that could worsen the scenario and/or interfere with the treatment. METHODS: The aim of the present investigation has been to assess the efficacy of a multifactorial treatment, including formoterol and megestrol acetate, in cachectic tumour-bearing rats (Yoshida AH-130, a highly cachectic tumour) undergoing chemotherapy (sorafenib). RESULTS: Treatment of cachectic tumour-bearing rats with sorafenib (90 mg/kg) causes an important decrease in tumour cell content due to both reduced cell proliferation and increased apoptosis. As a consequence, animal survival significantly improves, while cachexia occurrence persists. Multi-factorial treatment using both formoterol and megestrol acetate is highly effective in preventing muscle wasting and has more powerful effects than the single formoterol administration. In addition, both physical activity and grip strength are significantly improved as compared with the untreated tumour-bearing animals. The effects of the multi-factorial treatment include increased food intake (likely due to megestrol acetate) and decreased protein degradation, as shown by the reduced expression of genes associated with both proteasome and calpain proteolytic systems. CONCLUSIONS: The combination of the two drugs proved to be a promising strategy for treating cancer cachexia in a pre-clinical setting that better resembles the human condition, thus providing a strong rationale for the use of such combination in clinical trials involving cachectic cancer patients.