Progranulin is a novel independent predictor of disease progression and overall survival in chronic lymphocytic leukemia

Abstract

Progranulin (Pgrn) is a 88 kDa secreted protein with pleiotropic functions including regulation of cell cycle progression, cell motility, wound repair and tumorigenesis. Using microarray based gene expression profiling we have recently demonstrated that the gene for Pgrn, granulin (GRN), is significantly higher expressed in aggressive CD38(+)ZAP-70(+) as compared to indolent CD38(-)ZAP-70(-) chronic lymphocytic leukemia (CLL) cases. Here, we measured Pgrn plasma concentrations by enzyme-linked immunosorbent assay (ELISA) in the Essen CLL cohort of 131 patients and examined Pgrn for association with established prognostic markers and clinical outcome. We found that high Pgrn plasma levels were strongly associated with adverse risk factors including unmutated IGHV status, expression of CD38 and ZAP-70, poor risk cytogenetics (11q-, 17p-) as detected by flourescence in situ hybridization (FISH) and high Binet stage. Pgrn as well as the aforementioned risk factors were prognostic for time to first treatment and overall survival in this series. Importantly, these results could be confirmed in the independent multicentric CLL1 cohort of untreated Binet stage A patients (n = 163). Here, multivariate analysis of time to first treatment revealed that high risk Pgrn (HR = 2.06, 95%-CI = 1.13-3.76, p = 0.018), unmutated IGHV status (HR = 5.63, 95%-CI = 3.05-10.38, p<0.001), high risk as defined by the study protocol (HR = 2.06, 95%-CI = 1.09-3.89, p = 0.026) but not poor risk cytogenetics were independent prognostic markers. In summary our results suggest that Pgrn is a novel, robust and independent prognostic marker in CLL that can be easily measured by ELISA.

Conflict of interest statement

Competing Interests: The authors declare that no competing interests exist.

Figures

Figure 1. Progranulin plasma levels in CLL patients and normal blood donors.

ELISA analysis of plasma samples collected from CLL patients (N = 131) and normal blood donors (ND, N = 31) reveals statistically significant differences in Pgrn concentrations (Mann-Whitney U-Test). The bold horizontal bars represent the median and the whiskers indicate the interquartile range.

Figure 2. Correlation of Progranulin plasma levels and established prognostic markers in the CLL cohort from Essen.

Plasma samples collected from high-risk patients defined by the presence of unmutated IGHV genes (A), presence of del17p and/or del11q as detected by iFISH (B), expression of CD38 (C) and ZAP-70 (D), low percentage of smudge cells (E) as well as advanced Binet stage B/C (F) exhibited significantly higher Pgrn plasma concentrations as compared to low-risk patients. Statistical comparisons were made using the Mann-Whitney U-test (A–E) and Kruskall Wallis test (F). The bold horizontal bars represent the median and the whiskers indicate the interquartile range.

Figure 3. Association of Pgrn plasma levels and clinical outcome in the CLL cohort from Essen.

Kaplan-Meier curves depict the cumulative proportion of untreated (TTFT, A) and surviving (OS, B) patients with CLL. Statistical comparisons between patients with high (>165.5 ng/ml) and low Pgrn plasma levels (≤165.5 ng/ml) were performed using the log-rank test.

Figure 4. Time course analysis of Pgrn plasma levels and PB lymphocyte counts in stable vs. progressive CLL patients.

Sequential PB lymphocyte counts and corresponding Pgrn plasma levels in serial samples of nine individuals with stable (A and B) and nine patients with progressive disease (C and D). Lines connect the symbols of individual patients. The horizontal red dotted line in A and C represents the median Pgrn plasma concentration of the Essen CLL cohort.

Figure 5. Association of Pgrn plasma levels and clinical outcome in the multicentric CLL1 cohort.

Kaplan-Meier curves depict the cumulative proportion of progression free survival (PFS, A), time to first treatment (TTFT, B) and overall survival (OS, C) of patients with CLL. Statistical comparisons between patients with high (>79.2 ng/ml) and low Pgrn plasma levels (≤79.2 ng/ml) were performed using the log-rank test.