SLC1A5 and colorectal cancer: And while the interpretation of negative data is difficult, the lack of a contribution from these transporters is notable given that all six have been shown to be capable of mediating serine uptake in Xenopus oocytes and/or proteoliposomes.30–35,37,39,40,58 This is particularly true for ATB0+, which has very recently been shown to contribute to serine uptake in colorectal cancer cells.59 This suggests that there is likely a high level of context dependence in serine uptake, where the ability to transport serine in one context does not necessarily predict transport ability in another.