Abstract
Tumors develop an abnormal microenvironment during growth, and similar to the metastatic phenotype, the metabolic phenotype of cancer cells is tightly linked to characteristics of the tumor microenvironment (TME). In this study, we explored relationships between metabolic profile, metastatic propensity, and hypoxia in experimental tumors in an attempt to identify metastasis-associated metabolic profiles. Two human melanoma xenograft lines (A-07, R-18) showing different TMEs were used as cancer models. Metabolic profile was assessed by proton high resolution magic angle spinning magnetic resonance spectroscopy ((1)H-HR-MAS-MRS). Tumor hypoxia was detected in immunostained histological preparations by using pimonidazole as a hypoxia marker. Twenty-four samples from 10 A-07 tumors and 28 samples from 10 R-18 tumors were analyzed. Metastasis was associated with hypoxia in both A-07 and R-18 tumors, and (1)H-HR-MAS-MRS discriminated between tissue samples with and tissue samples without hypoxic regions in both models, primarily because hypoxia was associated with high lactate resonance peaks in A-07 tumors and with low lactate resonance peaks in R-18 tumors. Similarly, metastatic and non-metastatic R-18 tumors showed significantly different metabolic profiles, but not metastatic and non-metastatic A-07 tumors, probably because some samples from the metastatic A-07 tumors were derived from tumor regions without hypoxic tissue. This study suggests that (1)H-HR-MAS-MRS may be a valuable tool for evaluating the role of hypoxia and lactate in tumor metastasis as well as for identification of metastasis-associated metabolic profiles.