Antitumour 2-(4-aminophenyl)benzothiazoles generate DNA adducts in sensitive tumour cells in vitro and in vivo

Abstract

2-(4-Aminophenyl)benzothiazoles represent a potent and highly selective class of antitumour agent. In vitro , sensitive carcinoma cells deplete 2-(4-aminophenyl)benzothiazoles from nutrient media; cytochrome P450 1A1 activity, critical for execution of antitumour activity, and protein expression are powerfully induced. 2-(4-Amino-3-methylphenyl)benzothiazole-derived covalent binding to cytochrome P450 1A1 is reduced by glutathione, suggesting 1A1-dependent production of a reactive electrophilic species. In vitro , 2-(4-aminophenyl)benzothiazole-generated DNA adducts form in sensitive tumour cells only. At concentrations >100 n M , adducts were detected in DNA of MCF-7 cells treated with 2-(4-amino-3-methylphenyl)-5-fluorobenzothiazole (5F 203). 5F 203 (1 μ M ) led to the formation of one major and a number of minor adducts. However, treatment of cells with 10 μ M 5F 203 resulted in the emergence of a new dominant adduct. Adducts accumulated steadily within DNA of MCF-7 cells exposed to 1 μ M 5F 203 between 2 and 24 h. Concentrations of the lysylamide prodrug of 5F 203 (Phortress) ≥100 n M generated adducts in the DNA of sensitive MCF-7 and IGROV-1 ovarian cells. At 1 μ M , one major Phortress-derived DNA adduct was detected in these two sensitive phenotypes; 10 μ M Phortress led to the emergence of an additional major adduct detected in the DNA of MCF-7 cells. Inherently resistant MDA-MB-435 breast carcinoma cells incurred no DNA damage upon exposure to Phortress (⩽10 μ M , 24 h). In vivo , DNA adducts accumulated within sensitive ovarian IGROV-1 and breast MCF-7 xenografts 24 h after treatment of mice with Phortress (20 mg kg −1 ). Moreover, Phortress-derived DNA adduct generation distinguished sensitive MCF-7 tumours from inherently resistant MDA-MB-435 xenografts implanted in opposite flanks of the same mouse.

Antitumor Activity of a Duocarmycin Analogue Rationalized to Be Metabolically Activated by Cytochrome P450 1A1 in Human Transitional Cell Carcinoma of the Bladder

“…Involvement of CYP1A1 in cancer prodrug activation has been shown for aminoflavone AFP464 (32) and the benzothiazole Phortress (33) with binding to the AhR and a resultant induction of CYP1A1 expression being a critical step in their mechanism of action (32,34). CYP1A1-mediated DNA damage in tumors is identified as important to the antitumor activity of Phortress but also increases normal tissue toxicity, notably in the lung (35).…”

Cytochrome P450 pharmacogenetics and cancer

“…On the other hand, CYP1B1 mRNA and protein expression has been found in a wide range of malignant tumours and in metastatic disease (McFadyen et al, 2001a), but the CYP1B1 protein is generally not detected in normal tissue at important levels (Gibson et al, 2003). Taking advantage of this, several agents activated by CYP1B1 are currently in preclinical evaluation, such as resveratrol and phortress (Potter et al, 2002;Leong et al, 2003); in addition, there is a CYP1B1 vaccine (Zyc300) in phase I/II trials, aimed to destroy cancer cells through induction of T-cell response (Gribben et al, 2005). Similar strategies could be initiated with other P450s mainly identified in tumour cells, such as CYP2W1, CYP2J2 and CYP4Z1, after identification of an appropriate prodrug.…”

Synthesis and antitumor activity evaluation of new 2-(4-aminophenyl)benzothiazole derivatives bearing different heterocyclic rings

“…First, the original lead compound 2-(4-aminophenyl)benzothiazole (CJM 126, NSC34445), which was originally prepared as a synthetic intermediate in a program of screening for tyrosine-kinase inhibitors, was found to possess selective in vitro activity against MCF-7 breast carcinoma cell line. This discovery was followed by the identification of the 2-(4-amino-3-methylphenyl)benzothiazole (DF 203, NSC 674495) and 2-(4-amino-3-methylphenyl)-5-fluorobenzothiazole (5F 203, NSC 703786) and the evaluation of the analogue compounds with more potent and diverse activities [8][9][10][11][12][13][14] . Phortress (NSC 710305, dihydrochloride salt of the lysylamide prodrug of 2-(4-amino-3-methylphenyl)-5-fluorobenzothiazole (5F 203)), the fluorinated water-soluble pro-drug, which has been synthesized to address formulation and bioavailability issues related to the desired parenteral administration [15][16][17][18][19] , was then chosen for phase 1 The mechanism of action involves formation of reactive intermediates that can bind covalently to DNA and can be metabolized only by sensitive cancer cell lines 21 .…”

“…Unexpectedly, it was found that, 2-(4-aminophenyl)benzothiazole derivatives inhibit cancer cell growth with nanomolar scale against a large panel of human cancer cell lines particularly against breast, colon and ovarian cell lines in in vitro anticancer screening program of the National Cancer Institute (NCI) with a characteristic biphasic doseresponse relationship 6,7 . Up to present, scientists Shi and Bradshaw have a series of studies on antitumor activity of some benzothiazole derivatives [8][9][10][11][12][13][14] . First, the original lead compound 2-(4-aminophenyl)benzothiazole (CJM 126, NSC34445), which was originally prepared as a synthetic intermediate in a program of screening for tyrosine-kinase inhibitors, was found to possess selective in vitro activity against MCF-7 breast carcinoma cell line.…”