Peroxisome proliferator-activated receptor gamma (PPARgamma) is known to regulate growth arrest and terminal differentiation of adipocytes and is used clinically as a new class of antidiabetic drugs. Recently, several studies have reported that treatment of cancer cells with PPARgamma ligands induces cell differentiation and apoptosis, suggesting a potential application as chemopreventive agents against carcinogenesis. However, contradictory results have been reported with regards to the biologic role of PPARgamma in carcinogenesis. Tanaka et al.(24) have recently reported the suppressive effect of a PPARgamma ligand, troglitazone (Tro), on the formation of aberrant crypt foci (ACF) in rats. In the present study, 3 different kinds of PPARgamma ligands were subjected to the experiments to confirm their suppressive effects on colon carcinogenesis. Three PPARgamma ligands, pioglitazone (Pio) (200 ppm), rosiglitazone (Rosi) (200 ppm), and Tro (1000 ppm) were investigated on the induction of ACF, a putative precancerous lesion of the colon, and colon tumor formation using an azoxymethane (AOM)-induced colon cancer model in BALB/c mice, and dose dependency of a PPARgamma ligand was also examined. PPARgamma ligands reduced the ACF formation by AOM (10 mg/kg body weight) and induction of colon tumors were also markedly suppressed by a continuous feeding of Pio at 200 ppm. Our findings indicate that PPARgamma ligands are indeed potential chemopreventive agents for colon carcinogenesis.

It is often difficult to diagnose malignant lymphoma in the gastrointestinal tract using endoscopy. We report the case of ileocecal lymphoma diagnosed by probe-based confocal laser endomicroscopy (pCLE) (ColoFlex UHD, Cellvizio; Mauna Kea Technologies, Paris, France). The patient was a 52-year-old man who had a positive fecal occult blood test. He underwent colonoscopy and a tumor was found on the ileocecal valve ([Fig. 1]). A malignant tumor was suspected and a biopsy was taken. The lesion revealed high lymphocyte infiltration, but malignant lymphoma could not be diagnosed. Further multiple biopsies were taken, but a diagnosis could still not be reached. Subsequently, fluorescein-dripping pCLE [1] was performed. Within the lesion, pCLE identified numerous small cells with destruction of normal mucosal structure, which was similar to the image of malignant lymphoma that we have observed previously ([Fig. 2], [Video 1]) [2]. Polypectomy was performed, and histopathological assessment showed hyperplasia of moderate-to-large sized atypical lymphocytes ([Fig. 3]). The cells were immunohistochemically positive for CD20, CD79a, bcl-2, and bcl-6, and negative for CD3, CD5, CD10, and cyclin D1, which resulted in the pathological diagnosis of diffuse large cell lymphoma. The patient was diagnosed as stage I diffuse large cell lymphoma. The patient subsequently received chemotherapy. As the tumor cell size in the histopathological assessment was close to that of the small cells in the CLE image, we believe that what we observed using pCLE were the lymphoma cells. Endoscopy_UCTN_Code_CCL_1AC_2AH