Role of stromal microenvironment in drug resistance has been extensively reported for several cancers. We have demonstrated earlier that there is significant micro-environment mediated drug resistance (EM-DR) to arsenic trioxide (ATO) in acute promyelocytic leukemia (APL) and that this was predominantly driven by upregulation of the NF-ⱪB pathway in the malignant cell. In our current study we have probed the molecular mechanism of ATO resistance in further detail. The role of microRNA (miRNA) in mediating this cross talk, if any, has not been reported on. We undertook a study to evaluate the potential role played by miRNA in EM-DR to ATO in APL.

Using NGS based small RNA sequencing we identified two miRNA's that were differentially regulated in NB4 cells upon co-culture with HS-5 stromal cells (FDR corrected p values < 0.05). The two miRNAs were hsa-miR-23a-5p (downregulated) and hsa-miR-125a-3p (upregulated)](Fig 1a). These miRNAs have also been previously reported to be involved in NF-kB regulation, specifically miR125a-3p has been reported to be involved in activation of the NF-kB pathway and miR-23a- 5p can be repressed by the same pathway. These results were consistent with our earlier reported observations that NF-kB pathway is dysregulated and enhances drug resistance to ATO. We also observed miR-23a-5p mimics were able to restore the sensitivity of NB4 cells to ATO even in the presence of stromal cells (Fig 1b).

Consistent with the above small RNA sequencing and our previously reported microarray data, using quantitative proteomics approach we have identified that both NFkB signaling and metallothionein 2A (MT-2A) levels are upregulated in leukemic cells upon stromal co-culture. MT 2A is a known target for hsa-mir-23a-5p. MT's are known to sequester heavy metals such as arsenic and could potentially reduce their cytotoxic effect. The role of metallothionein in ATO resistance in APL and possibly other leukemia's needs further evaluation. This data along with that reported earlier by us illustrates multiple levels of regulation of the NF-kB pathway and resistance to ATO by stromal cell co-culture.

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Disclosures

No relevant conflicts of interest to declare.

Topics:
acute promyelocytic leukemia, arsenic trioxide, drug resistance, microbiology procedures, micrornas, nf-kappa b, coculture techniques, metallothionein, rna, small, arsenic

Author notes

*

Asterisk with author names denotes non-ASH members.

© 2016 by The American Society of Hematology
2016
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