MEISi Technology

First-in-class, selective, drug-like small molecule MEIS inhibitors 

MEIS Proteins as a drug target

Meis1 was first discovered in BXH-2 mouse leukemia model. Studies in the last decade have shown that Meis1 has crucial roles in cellular metabolism, redox state, and tumorigenesis. Meis1 maintains cytoplasmic glycolysis through transactivation of hypoxic tumor markers, namely Hif-1α and Hif-2α. MEIS proteins includes MEIS1, MEIS2 and MEIS3 proteins. MEIS proteins have been shown to interact with PBX and HOXA9 proteins. MEIS proteins are known as an oncogene and overexpressed in various cancers including leukemia. Intriguingly, a high level of Meis1 expression was found to be associated with resistance to conventional chemotherapies (Reviewed in  Current drug targets). 

We have used in silico, in vitro and in vivo approaches to identify small-molecule MEIS inhibitors (MEISi). In silico screening of a million druggable small molecules allowed us to identify putative MEISi. MEIS dependent luciferase reporter assays were used to validate in vitro efficacy of MEIS inhibitors. Small molecules named MEISi-1 and MEISi-2 demonstrated a significant inhibition of MEIS-luciferase activity. In addition, inhibition of MEIS protein resulted in downregulation of MEIS target gene expression in human and animal studies in ex vivo and in vivo, respectively. 

​Development of MEIS inhibitors

Meis1 is a member of three-amino-acid loop extension (TALE) homeodomain transcription factors. Studies in the last decade have shown that Meis1 has crucial roles in cardiac regeneration, stem cell function, and tumorigenesis. We have recently demonstrated that knocking out of Meis1 in adult cardiomyocytes resulted in the induction of cardiomyocyte proliferation. This suggests that targeting of Meis1 might be utilized in the manipulation of cardiomyocyte cell cycle post cardiac injuries. In addition, hematopoietic stem cell (HSC) specific deletion of Meis1 leads to in vivo expansion of HSCs pool. Thus, targeting Meis1 may lead to not only cell cycle entry but also ex vivo and in vivo expansion of HSCs. On the other hand, Meis1 transcriptionally regulates the expression of hypoxic tumor markers, namely Hif-1α and Hif-2α. Hif-1α and Hif-2α are involved in the induction of cytoplasmic glycolysis and scavenging of reactive oxygen species (ROS), respectively. Studies highlight emerging roles of Meis1 towards development of new therapeutic approaches in the treatment of myocardial injuries, bone failure, and cancer (Reviewed in  Current drug targets).

​Development of MEIS inhibitors
We have performed a number of analysis to develop small molecule MEIS inhibitors, which includes but not limited to;

1. in silico drug screening
2. in vitro luciferase assays
3. PCR pathway analyses
4. ex vivo validation studies
5. in vivo validation studies​​

​We have performed in silico screening of over 1 million small molecules which target MEIS homeodomain and are conducted in comparison to the other TALE homeodomains, have enabled to determine MEIS-specific hits

By means of the in vitro luciferase studies, the MEIS inhibitors which we have named as MEIS inhibitor-1 (MEISi-1) and MEIS inhibitor-2 (MEISi-2) were determined for the first time. These inhibitors (MEISi-1 and MEISi-2) inhibit MEIS luciferase reporter (Mahmoud &Kocabas et al, Nature, 2012) in a dose-dependent manner. 

It was found that MEISi-1 and MEISi-2, which are among the developed MEIS inhibitors, reduce expression of p21, Hif-1alpha (Hif-1α), Hif-2alpha (Hif-2α) genes in the Meis1 pathway in vitro and in vivo. 

MEIS Inhibitors modulate HSC activity

 (Meis1, which belongs to TALE-type class of homeobox gene family, appeared as one of the key regulators of hematopoietic stem cell (HSC) self-renewal and a potential therapeutical target. However, small molecule inhibitors of MEIS1 remained unknown. This led us to develop inhibitors of MEIS1 that could modulate HSC activity. To this end, we have established a library of relevant homeobox family inhibitors and developed a high-throughput in silico screening strategy against homeodomain of MEIS proteins using the AutoDock Vina and PaDEL-ADV platform. We have screened over a million druggable small molecules in silico and selected putative MEIS inhibitors (MEISi) with no predicted cytotoxicity or cardiotoxicity. This was followed by in vitro validation of putative MEIS inhibitors using MEIS dependent luciferase reporter assays and analysis in the ex vivo HSC assays. We have shown that small molecules named MEISi-1 and MEISi-2 significantly inhibit MEIS-luciferase reporters in vitro and induce murine (LSKCD34low cells) and human (CD34+, CD133+, and ALDHhi cells) HSC self-renewal ex vivo. In addition, inhibition of MEIS proteins results in downregulation of Meis1 and MEIS1 target gene expression including Hif-1α, Hif-2α and HSC quiescence modulators. MEIS inhibitors are effective in vivo as evident by induced HSC content in the murine bone marrow and downregulation of expression of MEIS target genes. These studies warrant identification of first-in-class MEIS inhibitors as potential pharmaceuticals to be utilized in modulation of HSC activity and bone marrow transplantation studies. Read more