Expression of ALK protein, mRNA and fusion transcripts in anaplastic large cell lymphoma

Systemic anaplastic large cell lymphoma (ALCL) can be divided into two subgroups, anaplastic lymphoma kinase (ALK)-positive and ALK-negative, based on the expression of ALK protein. Expression of this protein is due to genetic alterations of ALK at 2p23. Overall, observations on ALK protein, ALK mRNA, ALK-associated genetic alterations and their relationships, to one another are not often reported in the literature. In this study, we investigated the expression of ALK protein, mRNA and fusion transcripts involving ALK and their relationships in ALCL and analyzed formalin-fixed, paraffin-embedded tissues. Forty-five human cases were analyzed with immunohistochemistry for the ALK protein and RT-PCR for ALK mRNA and seven kinds of ALK involved fusion transcripts. Our results showed that the expression of ALK protein, ALK mRNA and ALK fusion transcripts were significantly related to one another (P < 0.01). Consistent with the expression of ALK protein, patients presenting with ALK mRNA or ALK involved fusion transcripts were significantly younger than those lacking ALK gene alteration (P < 0.01). This study demonstrates expression of both ALK protein and ALK mRNA are positively correlated with expression of ALK-associated fusion transcripts. Combined detection of ALK protein, ALK mRNA and ALK fusion transcripts can complement each other to aid in the diagnosis of ALCL.