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The combi-targeting concept: selective targeting of the epidermal growth factor receptor- and Her2-expressing cancer
Ranjita Banerjee1, Ying Huang, James P McNamee
1Department of Medicine, Division of Medical Oncology, McGill University Health Center/Royal Victoria Hospital, Montreal, Quebec, Canada.
Abstract:
Within the context of a new tumor-targeting strategy termed "combi-targeting," we designed RB24 to inhibit epidermal growth factor receptor (EGFR) or Her2 phosphorylation and to further degrade upon hydrolysis to 4-(3'-bromophenylamino)-6-aminoquinazoline (RB10; another EGFR/Her2 inhibitor) plus a strong DNA-alkylating species. 6-(3-Acetoxymethyl-3-methyltriazenyl)-4-(3'-bromophenylamino)quinazoline (RB24) showed significant antiproliferative activity against human breast cancer cells, and transfection of one such cell line, MDA-MB-435, with ErbB1 or ErbB2 (Her2) dramatically enhanced cell death by apoptosis. RB24 was capable of releasing 2- to 3-fold higher levels of RB10 in the transfectants than in their wild-type counterparts. More importantly, RB10 was abundantly distributed in the perinuclear region of the cells, and its elevated levels in the ErbB transfectants were concomitant with increased levels of DNA lesions in the latter cells. This selectivity could be abolished by coincubation of the cells with exogenous RB10, suggesting that the entire combi-molecule may bind primarily to its cognate perinuclear sites before degradation. This localization may exert a bystander effect, allowing the alkylating species to be abundantly propagated into the nucleus. Cell response to this novel targeting mechanism was mediated by 1) activation of c-Jun NH(2)-terminal kinase in response to DNA damage and 2) down-regulation of Bad through blockade of EGFR tyrosine kinase activity: two events that cooperatively converged into enhancement of apoptosis in the oncogene-transfected cells.
Insights
A novel drug, RB24, targets cancer cells by inhibiting epidermal growth factor receptor (EGFR) and Her2. It releases a DNA-damaging agent, enhancing cancer cell death, particularly in cells with high ErbB1 or ErbB2 expression.
Area of Science:
- Oncology
- Molecular Biology
- Medicinal Chemistry
Background:
- Targeted cancer therapies aim to selectively kill tumor cells while sparing normal tissues.
- Epidermal Growth Factor Receptor (EGFR) and Human Epidermal growth factor Receptor 2 (Her2) are key oncogenic drivers in various cancers, including breast cancer.
- Developing novel drug delivery systems that enhance drug accumulation and efficacy within cancer cells is crucial.
Purpose of the Study:
- To design and evaluate RB24, a novel combi-targeting agent, for its efficacy against human breast cancer cells.
- To investigate the mechanism of action of RB24, focusing on its inhibition of EGFR/Her2 and subsequent DNA damage.
- To assess the role of ErbB1 and ErbB2 (Her2) expression levels in mediating cellular response to RB24.
Main Methods:
- Synthesis and characterization of RB24, a dual-action EGFR/Her2 inhibitor and DNA alkylating agent.
- In vitro antiproliferative assays using human breast cancer cell lines, including those transfected to overexpress ErbB1 or ErbB2 (Her2).
- Analysis of RB10 release, cellular localization, DNA lesion formation, and downstream signaling pathways (e.g., c-Jun NH(2)-terminal kinase activation, Bad down-regulation).
Main Results:
- RB24 demonstrated significant antiproliferative activity against human breast cancer cells.
- Transfection with ErbB1 or ErbB2 (Her2) dramatically enhanced RB24-induced apoptosis, with 2- to 3-fold higher RB10 release compared to wild-type cells.
- RB10 accumulated in the perinuclear region, and its elevated levels in ErbB-transfected cells correlated with increased DNA damage, suggesting a combi-targeting mechanism.
Conclusions:
- RB24 represents a novel combi-targeting strategy that effectively inhibits EGFR/Her2 and induces DNA damage, leading to enhanced apoptosis in cancer cells with high ErbB expression.
- The perinuclear localization of RB10 and subsequent bystander effect on DNA damage highlight a unique mechanism of targeted drug delivery and action.
- RB24's efficacy is mediated by DNA damage response pathways and blockade of EGFR tyrosine kinase activity, offering a promising therapeutic candidate for ErbB-driven cancers.
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