Molecular Characterization By Cancer Immune Profiling in Acute Promyelocytic Leukemia (APL) May Identify Patients at Risk of Early Death

Background: APL is a highly curable malignancy with large co-operative group trials showing cure rates in excess of 90% and early mortality under 10%. Despite aggressive care, in the general population, 30% of patients die at presentation or shortly after initiation of treatment. Understanding the biology of the disease may help us identify the causes for these poor outcomes and allow for improvement in outcomes. Our study investigates the differences in expression genes involved in cancer immunology in APL patients with early mortality versus surviving patients.

Design: Archival blocks (n= 3 alive and n=4 early death) with slides were retrieved, reviewed and clinical information obtained from patient charts under approved IRB protocol. Several patient/disease characteristics were identified including age, sex, race, body mass index (BMI), and cytogenetics were noted. Therapy indicators such as treatment received, remission and relapse status was also noted. Seven 10μm sections of each case were used with >50% lesion. Total RNA was extracted from and analyzed with nanoString nCounter® using PanCancer Immune Profiling Panel designed to Perform multiplex gene expression analysis with 770 genes from 24 different immune cell types, common checkpoint inhibitors, CT antigens, and genes covering both the adaptive and innate immune response and housekeeping genes. Following hybridization and data acquisition, we used Partek Genomics Suite ® software for Robust Multi-array Average (RMA) normalization and to determine statistically significant differences in gene expression between experimental groups by ANOVA and pairwise comparisons (two-sided α=0.05).

Results: The gene expression profiles of dead versus alive patients shows statistically significant (1.5 to 12X, p<0.05) downregulation of a set of 11 genes, and upregulation of 8 genes (p<0.05) (Figure 1). Although the role of these genes has not been studied in APL, they have been extensively studied and characterized in other tumors with the dysregulation of cancer immune escape showing a role in tumor suppression, differentiation, cell proliferation, chemo resistance and inflammation.

Significance: To the best of our knowledge, the current study represents the first cancer immune profiling exploration in understanding the early death in APL patients. Toll-like receptors (TLRs) play a vital role in activating immune responses. Activation of tumor cell TLRs not only promotes tumor cell proliferation and resistance to apoptosis. Previous studies have demonstrated that that prevention of interferon regulatory transcription factor 3 (IRF3) phosphorylation (along with interferon (IFN)-β expression, STAT1 phosphorylation) is a critical downstream event in inhibitory effect of Arsenic trioxide (ATO) on Inducible nitric oxide synthase (iNOS) expression. This work is intriguing for the new information it provides about the cancer immune dysregulation of early deaths in APL.

Conclusions: We hypothesize that this dysregulation of cancer immune genes leads to a sustained proinflammatory state and also impart some resistance to an anti-inflammatory property of ATO that eventually leads to the poor outcomes. Further studies are needed to validate these results in a larger population and if confirmed can lead to better outcomes.