Abstract
We have previously reported the synthesis of SMA41, a unimolecular combination of an epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) of the quinazoline class and a DNA-damaging monomethyltriazene termed “combimolecule”. Hydrolysis of 1-[4-(m-tolylamino)-6-quinazolinyl]-3-methyltriazene (SMA41) gives rise to an intact TKI [6-amino-4-(3-methylanilino)quinazoline; SMA52] capable of inhibiting epidermal growth factor (EGF)-induced EGFR autophosphorylation and a DNA-targeting methyldiazonium species. Herein, we showed that SMA41 blocked EGF-induced EGFR autophosphorylation by an irreversible mechanism, suggesting that it may covalently damage the receptor in these cells. More importantly, this was associated with significant inhibition of mitogen-activated protein kinase activation in A431 cells. In cells treated with [14C]SMA41, radio-high-performance liquid chromatography detection of both N7- and O6-methylguanine revealed an almost complete repair of the O6-methylguanine lesions and a greater tolerance of the N7-methylguanine adducts 24 h post-treatment. In contrast to temozolomide (a cyclic triazene used in the clinic) and the reversible inhibitor SMA52, SMA41 induced significant cell cycle arrest in S, G2, and M phases 24 h after a 2-h drug exposure. Furthermore, in vivo studies demonstrated that SMA41 was well tolerated. At 200 mg/kg, it showed approximately 2-fold greater antiproliferative activity than SMA52 in A431 cells implanted in immunocompromised SCID mice. These results suggest that the binary targeting properties of SMA41 are associated with a binary cascade of events in the cells that seem to culminate into significant growth inhibition in vitro and in vivo.
Footnotes
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This study was funded by National Cancer Institute of Canada Grant 013377.
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.104.071977.
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ABBREVIATIONS: EGFR, epidermal growth factor receptor; TKI, tyrosine kinase inhibitor; MAP, mitogen-activated protein; SMA41, 1-[4-(m-tolylamino)-6-quinazolinyl]-3-methyltriazene; SMA 52, 6-amino-4-(3-methylanilino)quinazoline; PBS, phosphate-buffered saline; HPLC, high-performance liquid chromatography; HRP, horseradish peroxidase; AGT, O6-alkylguanine transferase.
- The American Society for Pharmacology and Experimental Therapeutics
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