A simple flow cytometry-based barcode for routine authentication of multiple myeloma and mantle cell lymphoma cell lines.

CELL lines are widely used in laboratories for in vitro experiments, especially for investigating abnormal hallmarks in cancer cells and identifying therapeutic targets. Human cell lines are typically derived in academic laboratories from a wide range of cancer samples. To achieve a representation of intracancer heterogeneity, several laboratories, including ours, have established cell line collections. However, the establishment and maintenance of such collections significantly increase the risk of cross-contaminations and misidentification of cell lines, leading to the publication of false data/interpretation (1). In addition to the risk of cross-contamination, widely used cell lines can be described in contrasting manners for a particular feature (e.g., the JJN3 myeloma cell line appears either TP53 wt or TP53, depending on the article), suggesting that cell lines may have been misidentified. ICLAC, the international cell line authentication committee, recommends cell lines authentication using single tandem repeat (STR) profiles that are usually performed by suppliers (2). Nevertheless, while cell lines are frozen and thawed at least four times per year, STR profile is assessed upon receipt of cell lines but not for routine assessment of cell lines identity. Because crosscontaminations might happen, a rapid and low-cost method for re-identification after each thawing of cells is required, as it is for mycoplasma detection. In this letter, we describe a simple and low cost method involving human leukocyte antigen (HLA) typing and phenotyping that could be used for routine re-authentication using flow cytometry. HLA typing is an international worldwide nomenclature dedicated to blood transfusion and organ transplant that identifies the HLA alleles carried by an individual (3,4). Initially performed for research projects in immunology, HLA Class I typing appears to be very useful for identification of cell lines (5,6). The genomic typing is performed at the generic (e.g., HLA-A*02) or specific (e.g., HLA-A*02:01) level with the generic typing usually being sufficient to identify cell lines within a dedicated collection. This genomic identification is particularly useful upon the inclusion of new cell lines within a collection and also for the establishment of derivatives such as drug-resistant cell lines, which could indicate the emergence of cryptic contaminating resistant cells within the parental cell lines. Our laboratory currently uses a large number of both human multiple myeloma cell lines (HMCLs, n 5 17) and mantle cell lymphoma cell lines (MCLCLs, n 5 8) that we have collected from ATCC, DSMZ, or from academic laboratories (7–9). Multiple myeloma (MM) and mantle cell lymphoma (MCL) are plasma cell and B cell malignancies, respectively. Independently of the global characterization of cell lines (karyotype, gene expression profile, characterization of TP53, and RAS mutations), the HLA Class I typing shown in Supporting Information Table S1 confirms that the cell lines examined were derived from independent individuals (7). To routinely check their identity using flow cytometry, we generated an algorithm that is based on HLA-A*02 expression and on the mutually exclusive expression of the kappa or lambda light chain of immunoglobulin. We used HLA-A*02 expression because HLA-A*02 is the most frequent allele in the population and because a specific mAb is commercially available. Expression of HLA-A*02, either positive or negative, segregated cell lines into two groups: kappa or lambda expression then segregated the cell lines into 2–3 subgroups (Tables 1 and 2). A minimum of markers with a global, stable, and selective expression (absent/present or low/bright expression) was then defined within each subgroup. As shown in Table 1