MR imaging of renal cortical tumours: qualitative and quantitative chemical shift imaging parameters

OBJECTIVES: To assess qualitative and quantitative chemical shift MRI parameters of renal cortical tumours. METHODS: A total of 251 consecutive patients underwent 1.5-T MRI before nephrectomy. Two readers (R1, R2) independently evaluated all tumours visually for a decrease in signal intensity (SI) on opposed- compared with in-phase chemical shift images. In addition, SI was measured on in- and opposed-phase images (SI(IP), SI(OP)) and the chemical shift index was calculated as a measure of percentage SI change. Histopathology served as the standard of reference. RESULTS: A visual decrease in SI was identified significantly more often in clear cell renal cell carcinoma (RCCs) (R1, 73 %; R2, 64 %) and angiomyolipomas (both, 80 %) than in oncocytomas (29 %, 12 %), papillary (29 %, 17 %) and chromophobe RCCs (13 %, 9 %; all, P < 0.05). Median chemical shift index was significantly greater in clear cell RCC and angiomyolipoma than in the other histological subtypes (both, P < 0.001). Interobserver agreement was fair for visual (kappa, 0.4) and excellent for quantitative analysis (concordance correlation coefficient, 0.80). CONCLUSIONS: A decrease in SI on opposed-phase chemical shift images is not an identifying feature of clear cell RCCs or angiomyolipomas, but can also be observed in oncocytomas, papillary and chromophobe RCCs. After excluding angiomyolipomas, a decrease in SI of more than 25 % was diagnostic for clear cell RCCs. KEY POINTS : • Chemical shift MRI offers new information about fat within renal tumours. • Opposed-phase signal decrease can be observed in all renal cortical tumours. • A greater than 25 % decrease in signal appears to be diagnostic for clear cell RCCs

Calnexin overexpression sensitizes recombinant CHO cells to apoptosis induced by sodium butyrate treatment

Sodium butyrate (NaBu) can enhance the expression of foreign genes in recombinant Chinese hamster ovary (rCHO) cells, but it can also inhibit cell growth and induce cellular apoptosis. In this study, the potential role of calnexin (Cnx) expression in rCHO cells treated with 5 mM NaBu was investigated for rCHO cells producing tumor necrosis factor receptor FC. To regulate the Cnx expression level, a tetracycline-inducible system was used. Clones with different Cnx expression levels were selected and investigated. With regard to productivity per cell (qp), NaBu enhanced the qp by over twofold. Under NaBu treatment, Cnx overexpression further enhanced the qp by about 1.7-fold. However, under NaBu stress, the cells overexpressing Cnx showed a poorer viability profile with a consistent difference of over 25% in the viability when compared to the Cnx-repressed condition. This drop in the viability was attributed to increased apoptosis seen in these cells as evidenced by enhanced poly (ADP-ribose) polymerase cleavage and cytochrome C release. Ca2+ localization staining and subsequent confocal imaging revealed elevated cytosolic Ca2+ ([Ca2+]c) in the Cnx-overexpressing cells when compared to the Cnx-repressed condition, thus endorsing the increased apoptosis observed in these cells. Taken together, Cnx overexpression not only improved the qp of cells treated with NaBu, but it also sensitized cells to apoptosis