Experimental therapy of doxorubicin resistant human uveal melanoma with targeted cytotoxic luteinizing hormone-releasing hormone analog (AN-152).

BACKGROUND

Cytotoxic analogs of LHRH (luteinizing hormone-releasing hormone) can be successfully used for the treatment of hormone-dependent cancers such as prostatic, ovarian, endometrial, but our knowledge about their effect on hormone-independent cancers such as human uveal melanoma (UM) is limited. Previously, we have demonstrated that 46% of UM express full-length LHRH receptors. This finding has led us to further examine the mechanism of action of LHRH receptor based targeted therapies in this malignancy.

AIMS

In the present study we investigated the cellular uptake of doxorubicin (DOX) and cytotoxic LHRH analog AN-152 (AEZS-108, zoptarelin doxorubicin) on human UM cell lines (OCM3) and its DOX resistant form OCM3 by confocal laser scanning microscopy. The LHRH receptor expression was characterized by RT-PCR and immunocytochemistry.

RESULTS

We were able to establish a new, stable and DOX resistant human UM cell line OCM3. Our results demonstrated the expression of splice variants and isoforms of receptor for LHRH in OCM3 UM cell line and its doxorubicin resistant form OCM3. It has been revealed by MTT assay that AN-152 inhibited cell proliferation in a dose dependent manner in OCM3 cells. Furthermore, receptor-mediated uptake of AN-152 was demonstrated using confocal laser scanning microscopy in both cell line.

CONCLUSIONS

Our results suggest that the antiproliferative effect of AN-152 can be detected even if only LHRH receptor isoforms are expressed. Our study also demonstrates the LHRH receptor-mediated uptake of AN-152 in DOX resistant OCM3 cells Our experiments provide new insights into a potential targeted therapy of UM and give further details about the accumulation of AN-152 in hormone-independent DOX-resistant cells expressing splice variants of the LHRH receptors.