The Mantle Cell Lymphoma Response to VCR Protocol Associated with Its Sensitivity to Hypomethylation Regulation-a Collateral Study on VCR Phase I Trial

Introduction:

Mantle cell lymphoma (MCL) is a malignancy of monomorphic small to medium-sized B lymphocytes and is considered incurable with standard chemotherapy. Median survival estimates are three to seven years, with even shorter survival times in patients with the blastoid variant and with higher proliferation rates. A number of chemotherapy regimens, both conservative and aggressive, have been employed to treat MCL. Many of these treatments, however, are highly toxic especially in elderly patients or patients with comorbidities. The lack of curative ability and high toxicity of current treatments gives rise to a need for a new regimen. Following a phase I trial utilizing bortezomib, cladribine and rituximab (VCR) (NCT01439750, Blood 2016 128:1792), a series of exploratory assays was utilized to help understand the effectiveness of this combination. It is well documented that cladribine has epigenetic effects and recently, it has been shown that epigenetic modulators play an important role in a variety of cancerous phenotypes. Considering this, we have hypothesized that a positive response to the VCR regimens can be linked to successful hypomethylation regulation of specific genes.

Methods:

Patients with relapsed or refractory MCL who met specific criteria were eligible to participate in this study. It was a single-arm open-label, investigator initiated phase 1 clinical trial to assess the safety and efficacy of combination treatment with bortezomib, cladribine, and rituximab. Following the completion of the clinical trial, a DNA methylation assay was performed to assess the biological factors involved in treatment response. Additionally, a cytokine analysis using a magnetic luminex assay was performed to further investigate possible biological dissimilarities that could account for differences in treatment response. The specific genes targeted in the cytokine analysis were PD-L1, CXCL12, IFN-gamma, Il-2, CXCL10, CXCL9, IL-15 and TNF.

Results:

A principal components analysis of the methylation data revealed that there were significant overall differences in the methylation patterns between patients who responded well and those who responded poorly to treatment. When evaluating genomic regions that differed between groups, it appeared that there was no difference in percentage of hypomethylated regions vs. hypermethylated regions. An analysis of specific genes that have known links to either cancer growth or B-cell production and growth, however, revealed possible targets to show epigenetic differences. Cytokine levels as well as methylation status at the TNF, PD-L1 and CXCL-12 genes were different between the two groups. Those who responded well exhibited significantly decreased methylation percentage at these genes whereas those who responded poorly indicated increased methylation or no change at all.

Discussion:

Using the methylation and cytokine assay results, we attempted to understand both the positive and negative outcomes of the drug regimen via the patient's genomic response. A previous study done with an ovarian cancer model showed that the TH1 chemokines CXCL-9 and CXCL-10 play a large role in epigenetic tumor modulation [Peng, et al, Nature. 2015, 527 (7577):249-53]. Despite not seeing any significant differences in these particular genes, the methylation changes noted at the CXCL-12 locus indicate a possible mechanism of detecting treatment effectiveness. The CXCR4/CXCL-12 axis plays an important role in cancer cell growth and treatment evasion. Activity in this area shows that the tumor is adapting to treatment, indicating effectiveness as well as a need for further intervention. Changes in the promoter region of PD-L1 and TNF are also possible targets for biomarkers of treatment effectiveness.