Sixty cancer cell lines have been extensively characterized and used by the National Cancer Institute's Developmental Therapeutics Program (NCI-60) since the early 90's as screening tools for anti-cancer drug development. An extensive database has been accumulated that could be used to select individual cells lines for specific experimental designs based on their global genetic and biological profile. However, information on the human leukocyte antigen (HLA) genotype of these cell lines is scant and mostly antiquated since it was derived from serological typing. We, therefore, re-typed the NCI-60 panel of cell lines by high-resolution sequence-based typing. This information may be used to: 1) identify and verify the identity of the same cell lines at various institutions; 2) check for possible contaminant cell lines in culture; 3) adopt individual cell lines for experiments in which knowledge of HLA molecule expression is relevant. Since genome-based typing does not guarantee actual surface protein expression, further characterization of relevant cell lines should be entertained to verify surface expression in experiments requiring correct antigen presentation.

The high prevalence of nasopharyngeal cancer (NPC) in Southern Asia and Mediterranean Northern Africa suggests genetic predisposition among other factors. While Human Leukocyte Antigen (HLA) haplotypes have been conclusively associated with NPC predisposition in Asians, Northern African Maghrebians have been less intensely studied. However, low resolution serological methods identified weak positive associations with HLA-B5, B13 and B18 and a negative with HLA-B14. Using sequence based typing (SBT), we performed a direct comparison of HLA class I frequencies in a cohort of 136 Tunisian patients with NPC matched for gender, age and geographical residence to 148 normal Tunisians. The bimodal age distribution of NPC in Maghrebians was also taken into account. HLA frequencies in normal Tunisians were also compared with those of Northern Moroccan Berbers (ME) to evaluate whether the Tunisian population in this study could be considered representative of other Maghrebian populations. HLA-B14 and -Cw08 were negatively associated with NPC (odd ratio = 0.09 and 0.18 respectively, Fisher p 2 -value = 0.0001 and = 0.003). Moreover, positive associations were observed for HLA-B-18, -B51 (split of -B5) and -B57 (p 2 -value < 0.025 in all) confirming previous findings in Maghrebs. The HLA-B14/Cw*08 haplotype frequency (HF) was 0.007 in NPC patients compared to 0.057 in both Tunisian (OR = 0.12; p 2 -value = 0.001) and Moroccan controls. This study confirms several previous associations noted by serologic typing between HLA class I alleles and the prevalence of NPC in Maghrebians populations. In addition, we identified a putative haplotype rare in Tunisian patients with NPC that may serve as a genetic marker for further susceptibility studies.

Sequence-based typing (SBT) is one of the most comprehensive methods utilized for HLA typing. However, one of the inherent problems with this typing method is the interpretation of ambiguous allele combinations which occur when two or more different allele combinations produce identical sequences. The purpose of this study is to investigate the probability of this occurrence. We performed HLA-A,-B SBT for Exons 2 and 3 on 676 donors. Samples were analyzed with a capillary sequencer. The racial distribution of the donors was as follows: 615-Caucasian, 13-Asian, 23-African American, 17-Hispanic and 8-Unknown. 672 donors were analyzed for HLA-A locus ambiguities and 666 donors were analyzed for HLA-B locus ambiguities. At the HLA-A locus a total of 548 total ambiguous allele combinations were identified (548/1344 = 41%). Most (278/548 = 51%) of these ambiguities were due to the fact that Exon 4 analysis was not performed. At the HLA-B locus 322 total ambiguous allele combinations were found (322/1332 = 24%). The HLA-B*07/08/15/27/35/44 antigens, common in Caucasians, produced a large portion of the ambiguities (279/322 = 87%). A large portion of HLA-A and B ambiguous allele combinations can be addressed by utilizing a group-specific primary amplification approach to produce an unambiguous homozygous sequence. Therefore, although the prevalence of ambiguous allele combinations is high, if the resolution of these ambiguities is clinically warranted, methods exist to compensate for this problem.

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