Provided herein are methods of treating cancer in a subject, by administering COH29 ((N-(4-(3,4-dihydroxyphenyl)-5-phenylthiazol-2-yl)-3,4-dihydroxybenzamide)). The methods of treating include treating a BRCA1-defective subject, a PARP1 inhibitor-resistant subject or a DNA-damaging anti-cancer agent resistant subject. The methods include treating cancer by administering COH29 and a DNA-damaging anti-cancer agent in a combined synergistic amount.