Targeted doxorubicin-containing luteinizing hormone-releasing hormone analogue AN-152 inhibits the growth of doxorubicin-resistant MX-1 human breast cancers.
Purpose: The receptors for luteinizing hormone-releasing hormone receptor (LHRH-R) are found in >50% of human breast cancers. Doxorubicin (DOX) was linked to [D-Lys 6 ]LHRH to form a cytotoxic conjugate, AN-152, which can be targeted to tumor cells expressing LHRH-R. We evaluated the effects of AN-152 on the estrogen-independent, DOX-resistant human mammary carcinoma line MX-1, xenografted into nude mice. Experimental Design: Nude mice bearing MX-1 tumors were administered five i.v. injections of AN-152 or DOX at doses equivalent to 3 mg/kg DOX. Tumor growth was followed, and changes in the expression of LHRH-R on tumors were evaluated by radioreceptor assays, reverse transcription-PCR, and Western blotting. The effects of AN-152 on the expression of human epidermal growth factor receptor (HER)-2 were investigated. Because LHRH-R are coupled to various G proteins, which are involved in mitogenic signaling, we determined the outcome of treatment with AN-152 on the levels of mRNA for different G proteins. Results: Treatment with AN-152 significantly ( P 3 , compared with the control tumors, which measured 2837.38 ± 515.38 mm 3 . Tumor doubling time was likewise significantly ( P i2 , and Gα 11 and the levels of HER-2 and HER-3 proteins were also significantly reduced by AN-152. Conclusions: Cytotoxic LHRH analogue AN-152 could be considered for targeted chemotherapy of DOX-resistant breast cancers expressing LHRH-R
