BPA uptake does not correlate with LAT1 and Ki67 expressions in tumor samples (results of EORTC trial 11001)

The system l-amino acid transporter (LAT1) imports p-boronophenylalanine (BPA) mainly into proliferating cells. This study investigates in three tumor entities whether the proportion of tumor cells expressing LAT1 and/or Ki67 correlates with BPA uptake. Tumors were analyzed for 10B concentration with prompt gamma-ray spectroscopy and for Ki67 and LAT1 expressions with immunohistochemical methods. The proportion of LAT1-expressing cells was much higher (5-90%) than that of Ki67-expressing cells (0-20%) and cells expressing both Ki67 and LAT1 (0-5%). Neither LAT1 nor Ki67 expression predicted BPA uptake.