Aim: K-ras proteins have been found mutated in about 35% of human tumors and appear to be an important factor for tumorigenesis. Its expression correlates with metabolic alterations such as increased glycolysis and glutamine consumption. This ability of cancer cells to decouple glucose and glutamine uptake reprogramming their metabolism leads to a more efficient use of nutrients in order to support cell proliferation and represents an interesting target for cancer therapy. Aim of this study is to investigate the metabolic alterations occurring in k-ras transformed fibroblasts combining in vivo and in vitro studies. Materials and methods: nu/nu mice were subcutaneously implanted with 2.5 x 105 k-ras transformed murine NIH3T3 fibroblasts (oncogenic k-ras) or with 2.5 x 105 murine fibroblasts with the dominant negative mutation on GEF protein that attenuates k-ras activation reverting to the wild type phenotype (reverted). Lesions size was constantly monitored with calliper and volumes calculated as (L x l2)/2 mm3. Animals performed [18F]FDG- and [18F]FLTPET studies at several time points starting with a tumor dimension consistent with animal PET spatial resolution (approximately 2mm). Images were calibrated, corrected for isotope half-life and elaborated with PMOD software to calculate Standardized Uptake Value (SUVmax). Finally, animals were sacrificed and tumor collected for metabolomic analysis. Results: All animals injected with oncogenic k-ras fibroblasts develop in few days fast growing, aggressive and highly glycolytic tumors that appear homogeneous for both [18F]FDG and [18F]FLT SUV values. On the contrary, 40% of k-ras reverted animals develop heterogeneous tumors at later time. Among k-ras reverted animals, two distinct tumor phenotypes can be observed: small, slow growing and poor glycolitic tumors with low uptake of both tracers, and small, slow growing but highly glycolytic and proliferating tumors that present SUVmax values comparable to those of k-ras oncogenic tumors. A good correlation, even if not significant, between tumor volume and [18F]FLT SUVmax has been observed for oncogenic k-ras animals. Conclusions:PET imaging is an accurate in vivo technique able to visualize and monitor tumor development in the k-Ras fibroblasts mouse model. K-Ras transformed fibroblasts give rise to aggressive and fast-growing tumors that represent a good model to study the efficacy of cell metabolism based therapy. Finally, K-Ras reverted tumors need further investigations to understand the interaction among tumor microenvironment, metabolic alterations and genetic component that may trigger tumor development.
Assessing cancer metabolic remodeling in animal models using PET imaging
Gaglio D;Valtorta S;Belloli S;Di Grigoli G;Todde S;Moresco R M
2013
Abstract
Aim: K-ras proteins have been found mutated in about 35% of human tumors and appear to be an important factor for tumorigenesis. Its expression correlates with metabolic alterations such as increased glycolysis and glutamine consumption. This ability of cancer cells to decouple glucose and glutamine uptake reprogramming their metabolism leads to a more efficient use of nutrients in order to support cell proliferation and represents an interesting target for cancer therapy. Aim of this study is to investigate the metabolic alterations occurring in k-ras transformed fibroblasts combining in vivo and in vitro studies. Materials and methods: nu/nu mice were subcutaneously implanted with 2.5 x 105 k-ras transformed murine NIH3T3 fibroblasts (oncogenic k-ras) or with 2.5 x 105 murine fibroblasts with the dominant negative mutation on GEF protein that attenuates k-ras activation reverting to the wild type phenotype (reverted). Lesions size was constantly monitored with calliper and volumes calculated as (L x l2)/2 mm3. Animals performed [18F]FDG- and [18F]FLTPET studies at several time points starting with a tumor dimension consistent with animal PET spatial resolution (approximately 2mm). Images were calibrated, corrected for isotope half-life and elaborated with PMOD software to calculate Standardized Uptake Value (SUVmax). Finally, animals were sacrificed and tumor collected for metabolomic analysis. Results: All animals injected with oncogenic k-ras fibroblasts develop in few days fast growing, aggressive and highly glycolytic tumors that appear homogeneous for both [18F]FDG and [18F]FLT SUV values. On the contrary, 40% of k-ras reverted animals develop heterogeneous tumors at later time. Among k-ras reverted animals, two distinct tumor phenotypes can be observed: small, slow growing and poor glycolitic tumors with low uptake of both tracers, and small, slow growing but highly glycolytic and proliferating tumors that present SUVmax values comparable to those of k-ras oncogenic tumors. A good correlation, even if not significant, between tumor volume and [18F]FLT SUVmax has been observed for oncogenic k-ras animals. Conclusions:PET imaging is an accurate in vivo technique able to visualize and monitor tumor development in the k-Ras fibroblasts mouse model. K-Ras transformed fibroblasts give rise to aggressive and fast-growing tumors that represent a good model to study the efficacy of cell metabolism based therapy. Finally, K-Ras reverted tumors need further investigations to understand the interaction among tumor microenvironment, metabolic alterations and genetic component that may trigger tumor development.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
