Acute myeloid leukemia (AML) has a poor prognosis under the current standard of care. In recent years, venetoclax, a BCL-2 inhibitor, was approved to treat patients, ineligible for intensive induction chemotherapy. Complete remission rates with venetoclax-based therapies are, however, hampered by minimal residual disease (MRD) in a proportion of patients, leading to relapse. MRD is due to leukemic stem cells retained in bone marrow protective environments; activation of the CXCL12/CXCR4 pathway was shown to be relevant to this process. An important role is also played by cell adhesion molecules such as CD44, which has been shown to be crucial for AML development. Here we show that CD44 is involved in CXCL12 promotion of resistance to venetoclax-induced apoptosis in human AML cell lines and AML patient samples which could be abrogated by CD44 knockdown, knockout or blocking with an anti-CD44 antibody. Split-Venus biomolecular fluorescence complementation showed that CD44 and CXCR4 physically associate at the cell membrane upon CXCL12 induction. In the venetoclax-resistant OCI-AML3 cell line, CXCL12 promoted an increase in the proportion of cells expressing high levels of embryonic-stem-cell core transcription factors (ESC-TFs: Sox2, Oct4, Nanog), abrogated by CD44 knockdown. This ESC-TF-expressing subpopulation which could be selected by venetoclax treatment, exhibited a basally-enhanced resistance to apoptosis, and expressed higher levels of CD44. Finally, we developed a novel AML xenograft model in zebrafish, showing that CD44 knockout sensitizes OCI-AML3 cells to venetoclax treatment in vivo. Our study shows that CD44 is a potential molecular target to sensitize AML cells to venetoclax-based therapies.
Transcriptional inhibition by small interfering RNA (siRNA) delivery using synthetic transfection agents eliminates the subsequent risk of introducing mutations in relevant genes, as opposed to viral vectors. However, synthetic vectors with comparable transfection efficiency to that of viral vectors are yet to be developed. Hence, synthesizing new transfection vehicles with low toxicity is important. In this study, a library of lipid-like molecules (lipidoids) was synthesized by thiolactone chemistry. This library facilitated nonviral delivery of siRNA to mammalian cells, inducing sequence-specific knockdown of a target gene. The liposomal nanoparticles complexed with anti-green fluorescent protein (GFP) siRNA were successfully screened for transfection efficiency using a HeLa-GFP cell line. The five best-performing lipidoids identified in the screening were found to exhibit superior GFP-knockdown efficiency compared with commercially available transfection reagents. The efficiency of siRNA delivery by one of these lipidoids with minimal toxicity was further successfully evaluated in vivo using Kdrl:EGFP zebrafish embryos as a model system. Our study would be important as a facile synthetic route of efficient nonviral nucleic acid delivery to live cells and organisms.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.