CXCR6 and glioblastoma: We verified the expression of CXCL16 and the lack of CXCR6 in human glioblastoma cell lines A172, LN229, T98G and U251MG on mRNA level by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and on protein level by immunocytochemistry (ICC) for cell lines used in the following sections (Figure 1A; compare also [13] for independent results on T98G and A172).