mithramycin-sk and Ovarian-Neoplasms

Differential cleavage at three restriction enzyme sites was used to determine the specific binding to DNA of the antitumour antibiotics mithramycin A (MTA), chromomycin A(3) (CRO) and six chromophore-modified analogues bearing shorter side chains attached at C-3, instead of the pentyl chain. All these antibiotics were obtained through combinatorial biosynthesis in the producer organisms. MTA, CRO and their six analogues showed differences in their capacity for inhibiting the rate of cleavage by restriction enzymes that recognize C/G-rich tracts. Changes in DNA melting temperature produced by these molecules were also analyzed, as well as their antiproliferative activities against a panel of colon, ovarian and prostate human carcinoma cell lines. Moreover, the cellular uptake of several analogues was examined to identify whether intracellular retention was related to cytotoxicity. These experimental approaches provided mutually consistent evidence of a seeming correlation between the strength of binding to DNA and the antiproliferative activity of the chromophore-modified molecules. Four of the analogues (mithramycin SK, mithramycin SDK, chromomycin SK and chromomycin SDK) showed promising biological profiles.

Topics: Antibiotics, Antineoplastic; Cell Line, Tumor; Chromomycin A3; Chromomycins; Colonic Neoplasms; Deoxyribonucleases, Type II Site-Specific; DNA Restriction Enzymes; Female; Flow Cytometry; Humans; Male; Ovarian Neoplasms; Plicamycin; Prostatic Neoplasms; Structure-Activity Relationship

Increased activity of Sp family of transcription factors is a frequent and critical event in cancer development and progression. Genes governing tumor growth, invasion and angiogenesis are regulated by Sp factors, like Sp1, Sp3 or Sp4, and are frequently over-expressed in tumors. Targeting Sp factors has been explored as a therapeutic approach. Mithramycin (MTM) is a natural antibiotic that binds DNA and inhibit Sp1-dependent transcription. New analogues, named MTM-SDK and MTM-SK, were recently obtained by genetic engineering of the MTM biosynthetic pathway and have demonstrated improved transcriptional and antiproliferative activity in ovarian cancer cell lines in vitro. In the present study we evaluated the activity of the new compounds in human ovarian cancer xenografts.. Expression of Sp1 and target proteins in ovarian cancer specimens and tumor xenografts was assessed by immunohistochemistry. Drug-induced silencing of Sp1-regulated genes in cells and tumor xenograft samples was assessed by quantitative RT-PCR. Toxicity and antitumor activity of the compounds were investigated in healthy and tumor-bearing immunocompromised mice, respectively.. Expression of Sp1 was frequently increased in human epithelial ovarian cancers. MTM-SDK and MTM-SK acted as potent inhibitors of Sp1-dependent transcription both in vitro and in tumor xenografts. Both compounds were well tolerated even after prolonged administration and delayed growth of ovarian tumor xenografts. MTM-SDK was particularly effective against orthotopic tumors leading to a significant increase of survival and delay of tumor progression.. MTM-SDK and MTM-SK show relevant activity in vivo and represent interesting candidates for treatment of ovarian cancers.

Topics: Animals; Antibiotics, Antineoplastic; Cell Growth Processes; Female; Gene Expression Regulation, Neoplastic; Humans; Mice; Mice, Nude; Ovarian Neoplasms; Plicamycin; Sp1 Transcription Factor; Xenograft Model Antitumor Assays