We used gene expression profiling to probe differences in transcriptional output between 15 panels of colon tumor and matched normal colon tissues. This analysis revealed that GPR49, an orphan G Protein-Coupled Receptor (GPCR) is overexpressed in 66% (10/15) colon tumors compared with normal colon tissues. Subsequent analysis of an additional 39 sets of matched normal and tumor colon tissues by real-time quantitative reverse transcriptase confirmed the upregulation of this receptor. The differential expression of GPR49 between normal and tumor tissue was significant (p > 0.001). GPR49 was upregulated in 25 of 39 (64%) colon primary tumor tissues. In addition to colon tumors, GPR49 was also found to be upregulated in 18 of 33 (53%) ovarian primary tumor tissues analyzed by RT-PCR. Moreover, the expression level of GPR49 in colon and ovarian tumors increased in more advanced tumors suggesting a role for the receptor in tumor progression. The selective overexpression of GPR49 in tumor tissues was further illustrated by specific immunohistochemical staining of colon and ovarian tumor tissues, a finding that correlates with the mRNA expression of the receptor. In addition, expression of GPR49 induced transformation in a ligand-dependent manner and Knockdown of GPR49 mRNA level induced apoptosis in colon tumor cells. These novel findings provide a foundation for further studies and suggest a potential role for GPR49 in tumorigenesis.

We studied the effect of cholecalciferol (VD3) intake on VD3 status and markers of calcium (Ca) homeostasis in mice and rats. Serum 25 hydroxycholecalciferol (25OH-VD3) concentrations were increased in animals fed diets containing 400-20,000 international units (IU) VD3/kg (37 nmol.L(-1).1000 IU VD3(-1)), but body weight, serum Ca, and duodenal gene expression were not altered. High-VD3 intake decreased serum 1, 25-dihydroxycholecalciferol [1,25(OH)2-VD3] and renal 25 hydroxycholecalciferol-1alphahydroxylase (CYP27B1) mRNA, suggesting that rodents tolerate high-VD3 intake by suppressing the activity of the VD3 endocrine system. Serum 25OH-VD3 declined when animals were fed diets containing 1000 to 25 IU VD3/kg (9-11 wk, inflection at 200 IU/kg, 4-fold steeper slope below this). Neither body weight nor serum Ca were influenced by low-VD3 intake. However, mice fed the 25-IU/kg diet had lower serum 1,25(OH)2-VD3, duodenal calbindin D9k mRNA, bone mineral density, and renal 25 hydroxycholecalciferol-24 hydroxylase mRNA, whereas renal CYP27B1 mRNA was elevated when rodents were fed < 200 IU VD3/kg. These data reveal a stress on VD3 and Ca metabolism at low dietary VD3 intake. Dietary Ca restriction (0.25 vs. 0.5%, 9 wk) increased serum 1,25(OH)2-VD3 and was 30% greater in rats fed a 10,000-IU VD3/kg diet. High-VD3 intake did not prevent Ca restriction-induced bone loss. Our data show that modeling human VD3 status requires lower intake than the current NRC rodent requirement (1000-IU/kg diet). Also, although rodents are very tolerant of high-VD3 intake, it cannot compensate for moderate Ca restriction.

Unlike many cancers which exhibit glycolytic metabolism, high grade liposarcomas often exhibit low FDG uptake by PET despite rapid tumor growth. Here, we used liquid chromatography tandem mass spectrometry to identify carbon sources taken up by liposarcoma cell lines derived from patient xenograft tumors. Interestingly, we found that liposarcoma cell lines consume nucleosides from culture media, suggesting nucleoside salvage pathway activity. The nucleoside salvage pathway is dependent on deoxycytidine kinase (dCK) (1) and can be imaged in vivo by PET with 1-(2′-deoxy-2′-[18F]fluoroarabinofuranosyl) cytosine (FAC) (2). We found that liposarcoma cell lines and xenograft tumors exhibit dCK activity and dCK-dependent FAC uptake in vitro and in vivo. Additionally, liposarcoma cell lines and xenograft tumors are sensitive to treatment with the nucleoside analog prodrug gemcitabine, and gemcitabine sensitivity is dependent on dCK expression. Elevated dCK activity is evident in 7 out of 68 clinical liposarcoma samples analyzed. This data suggests that a subpopulation of liposarcoma patients have tumors with nucleoside salvage pathway activity that can be identified non-invasively using [18F]-FAC-PET and targeted using gemcitabine.