Alanine-serine-cysteine transporter 2 (ASCT2), a neutral amino acids transporter, plays a central role in sustaining glutamine metabolism. L-type amino acid transporter 1 (LAT1), a large neutral amino acids transporter, transports most of the essential amino acids. Both of them are highly expressed in various type of cancers. In the present study, we investigated the combinational effect of ASCT2 inhibitor and LAT1 inhibitor in four colorectal cancer cell lines in cell proliferation experiments in vitro. Treatment with ASCT2 or LAT1 inhibitor alone showed limited growth inhibition in all the tested cell lines. Treatment with the combination of two inhibitors showed prominent synergistic growth inhibition in two cell lines, additive growth inhibition in one cell line, while there was no obvious combinational effect in the remaining one cell line. LAT1 and ASCT2 expression, transport function, amino acids content and signaling in these cell lines will be further studied, to reveal the cellular determinants underling the difference among cell lines. The results of this study may contribute to propose combinational treatment for colorectal cancers using inhibitors of the two amino acid transporters.