[Methyl-14C]-choline incorporation into nude mice bearing tumor xenografts-correlation with [methyl-3H]-thymidine: A pilot study

Background: Many in vitro studies suggested that choline incorporation into many types of tumors is related to cell proliferation. Whether in vivo choline incorporation is related also to cell proliferation or not was my question. Therefore, the aim of this pilot study was to investigate the relationship of in vivo [methyl- 14C]-choline incorporation and in vivo [methyl-3H]- thymidine incorporation. Materials and Methods: Four female nude mice were inoculated with MCF-7 breast tumor cells. Tumors were allowed to grow to a diameter of 0.5 cm and a diameter of 1 cm. Radioactivity of 370 kBq [methyl-14C]-choline and [methyl-3H]-thymidine each was injected. After 10 min, tumors were harvested and extracted with organic and aqueous solvents. The total [methyl-3H]-thymidine and [methyl-14C]-choline were determined and correlated using Spearman's rank (rs) coefficient at 0.5 cm (n=4) and 1 cm (n=3) tumors. Results: Spearman's rank (rs) correlation coefficient showed high rs=0.8 (p=0.2 n=4) at 0.5 cm tumor compared to low rs=0.5 (p=0.7 n=3) at 1 cm tumor. Conclusion: In this preliminary pilot study, in vivo [methyl-14C]-choline incorporation may correlate with cell proliferation. More number of investigations is recommended.