Quantification of ZAP-70 mRNA by real-time PCR is a prognostic factor in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is heterogeneous with respect to prognosis and clinical outcome. Mutational status of immunoglobulin heavy chain variable region (IGHV) appears to be a particularly strong prognostic marker, but it is difficult to perform in a routine clinical laboratory. ζ-chain-associated protein kinase 70 kDa (ZAP-70) protein detected by flow cytometry is a strong surrogate marker of IGHV mutational status; however, it suffers from the lack of standardization.

We investigated whether ZAP-70 mRNA expression level can be a prognostic factor in CLL. Real-time quantitative polymerase chain reaction was used to analyze ZAP-70 mRNA expression from 102 CLL patients.

The expression of ZAP-70 mRNA was significantly associated with Binet stage (P < 0.001), lactate dehydrogenase (P = 0.003), ZAP-70 protein (P = 0.018), IGHV mutational status (P = 0.038), and cytogenetic abnormality of del(17p13) or del(11q22.3) (P = 0.037) in CLL patients. According to receiver operating characteristic curve analysis for ZAP-70 mRNA and ZAP-70 protein, positive ZAP-70 mRNA (P = 0.006) was an adverse factor in determining the treatment free survival (TFS). In a multivariate Cox analysis of TFS, ZAP-70 mRNA is not ideal as an independent prognostic factor. However, ZAP-70 mRNA was statistically significant in predicting treatment response.

This study demonstrated the value of determination of ZAP-70 mRNA in providing useful prognostic information in CLL patients. However, ZAP-70 mRNA is not an independent prognostic factor.