Towards CD177 As a Predictive Biomarker for Hypomethylating Agent Response in Myelodysplastic Syndrome

Background

Myelodysplastic syndrome (MDS) represents a heterogenous spectrum of pre-leukemic conditions with a wide range of outcomes. Higher risk MDS as classified by the revised international prognostic scoring system (IPSS-R) score is associated with poor overall survival and up to 30% of patients progressing to acute myeloid leukemia. Hypomethylating agents (HMA) such as azacitadine can improve cytopenias and delay progression to leukemia in about 30% of patients, but these agents may take months to promote response and initially exacerbate cytopenias. Thus treatment related biomarkers that help predict eventual hematologic response are of interest.

CD177 is expressed in neutrophils and plays a role in cellular adhesion. In healthy cells, it exhibits bimodal expression by flow cytometry that is stable over time within an individual. The percentage of CD177 positive neutrophils is often decreased in hematopoietic malignancies and myelodysplastic syndromes. Our group has demonstrated that CD177 has diagnostic utility in the identification of myelodysplastic syndromes. As transcription of CD177 is regulated by CpG methylation of its promotor, we hypothesized that treatment with HMAs may improve CD177 expression in clinical responders and potentially guide continuation of HMA therapy.

Methods

To interrogate the above, we performed a retrospective review of patients with a diagnosed with MDS or MDS/MPN overlap syndromes who received disease modifying therapy with HMA at our institution from 2015 to 2018. Inclusion criteria required documentation of serial bone marrow biopsies with aspirate flow cytometry analysis. CD177 positivity was determined by increase in mean florescence intensity compared to isotype controls. Data was analyzed with using cox multivariate and univariate analysis correlating to treatment response.

Results

Of the 237 patients, 27 patients met the above criteria. Their average age was 62 (21 to 77) at time of diagnosis with 20 men and 7 women. They exhibited a range of R-IPSS risk stratification with four very high risk, eight high risk, six intermediate risk, and four low risk. Five cases were MDS/MPN overlap. Patients received on average 10 months of HMA treatment with a wide range from 1 month to 42 months of treatment. Median baseline CD177 positivity was 16, 31, 28.5, and 72 percent respectively amongst R-IPSS groups.

Of the 27 patients analyzed with repeat bone marrow biopsies, eight patients exhibited 20% or greater increase in CD177(+) neutrophils, ten exhibited a decrease in CD177(+) neutrophils of 20% or greater, and nine exhibited less than a 20% change in CD177(+) neutrophils. with similar distribution of R-IPSS risk stratification amongst groups. (CD177-decreased: 1 very high, 3 high, 1 intermediate, 2 low risk, CD177-stable 1 very high, 2 high, 2 intermediate, and 1 low, Improved-CD177 1 very high, 4 high, 2 intermediate and 1 low). Cox proportional hazard analysis suggests that patients exhibiting a decrease or stable CD177 were less likely to exhibit a treatment response with results trending to significance (OR= 0.13 p=0.099).

Conclusion

Our initial data suggests that change in CD177 may help predict HMA treatment response. More uniform prospective analysis is indicated to compared CD177 changes over initial treatment. Furthermore, CD177 in peripheral blood and bone marrow samples correlate excellently (R ²=0.95). Prospective studies are underway to correlate CD177 change and initial treatment response utilizing flow analysis of pre-treatment CBCs.