MGMT Is a Molecular Determinant for Potency of the DNA-EGFR–Combi-Molecule ZRS1

Abstract

To enhance the potency of current EGFR inhibitors, we developed a novel strategy that seeks to confer them an additional DNA damaging function, leading to the design of drugs termed combi-molecules. ZRS1 is a novel combi-molecule that contains an EGFR tyrosine kinase targeting quinazoline arm and a methyltriazenebased DNA damaging one. We examined its effect on human tumor cell lines with varied levels of EGFR and O6-methylguanine DNA methyltransferase (MGMT). ZRS1 was more potent than the clinical methylating agent temozolomide in all cell lines, regardless of their MGMT status. However, its potency was in the same range as or less than that of Iressa, an EGFR inhibitor, against MGMT-proficient cells. In the MGMTdeficient or in MGMT-proficient cells exposed to the MGMT inhibitor O6-benzylguanine, its potency was superior to that of Iressa and temozolomide or a temozolomideþIressa combination. Cell signaling analysis in A549 (MGMT þ ) and A427 (MGMT -) showed that ZRS1 strongly inhibited EGFR phosphorylation and related signaling pathways. In addition, the p53 pathway was activated by DNA damage in both cell lines, but apoptosis was significantly more pronounced in A427 cells. Using MGMT shRNA to block endogenous MGMT protein expression in A549 resulted in significant sensitization to ZRS1. Furthermore, transfection of MGMT into A427 greatly decreased the potency of ZRS1. These results conclusively show that MGMT is a critical molecular determinant for the full-blown potency of the dual EGFR-DNA targeting combi-molecule. Mol Cancer Res; 9(3); 320-31. Ó2011 AACR.

Advances in the development of hybrid anticancer drugs

“…The combi-molecule strategy aims to the vectorization of anticancer drugs to target specific tissues is also a promising method to design highly effective, non-toxic and useful hybrids. Compound 97 is a hybrid connecting also aromatic nitrogen mustards (40)(41)(42) and tyrosine that was designed to mimic the estradiol nucleus [55]. Compound 97 exhibits antiproliferative activity in the M range on prostate, breast, ovarian and uterine cancer cell lines and was slightly more active than chlorambucil (41).…”

Molecular analysis of the dual targeting of the epidermal growth factor receptor and the O6-methylguanine-DNA methyltransferase with a double arm hybrid molecule

“…EGFR is one of the most investigated receptor tyrosine kinases in the context of DNA repair. Through the mitogen-activated protein kinase (MAPK) pathway, EGFR activation leads to expression of DNA repair genes [ 11 ] and through the phosphatidylinositol-3 kinase (PI3K) pathway, it exerts an antiapoptotic effect [ 12 ]. Based on the premise that activation of EGFR leads to induction of DNA repair proteins such as X-ray repair cross-complementing protein 1 (XRCC1) and excision repair cross-complementation group 1 (ERCC1), our group embarked onto the design of drugs termed “combi-molecules” that can induce a tandem targeting of EGFR and DNA and demonstrated that indeed the latter dual targeted molecules could down-regulate XRCC1 and ERCC1 through their EGFR inhibitory arm and inducing high levels of DNA strand breaks through their DNA alkylating arm [ 11 ].…”

“…Promoter methylation of MGMT is now clinically used in the management of glioblastoma multiforme [ 13 ]. Importantly, questions relative to the association between EGFR activation and MGMT-mediated repair has been molecularly and pharmacologically addressed by our group [ 12 ]. Using double arm combi-molecules designed to down-regulate EGFR and methylate DNA, we demonstrated that MGMT expression was uncoupled with down-regulation of EGFR signaling.…”

“…Indeed, we previously showed that a single molecule designed to block EGFR and damage DNA could block EGFR phosphorylation and its downstream RAF-MAPK and PI3K-AKT pathways, induce p53 and Bax and ultimately trigger apoptosis in tumour cells. However, in a panel of cells with varied levels of MGMT, it was found that its potency was partly mitigated by MGMT expression [ 12 ]. Here, we sought to study a model whereby, a single molecule can exhibit multiple effects associated with EGFR inhibition in addition to down-regulate MGMT.…”

A type I combi-targeting approach for the design of molecules with enhanced potency against BRCA1/2 mutant- and O6-methylguanine-DNA methyltransferase (mgmt)- expressing tumour cells

“…A549 (ATCC® CCL-185™), DU145 (ATCC® HTB-85™), and A427 (ATCC® HTB-53™), was purchased from ATCC. A427-MGMT was obtained by stable transfection of A427 with MGMT viral vector in our lab [ 26 ]. All cell lines were maintained in in DMEM media from Wisent Bio Products.…”