Novel C,N-chelate rhodium(III) and iridium(III) antitumor complexes incorporating a lipophilic steroidal conjugate and their interaction with DNA

Dalton Trans. 2012 Nov 7;41(41):12847-56. doi: 10.1039/c2dt31654d. Epub 2012 Sep 17.

Abstract

The novel steroidal conjugates [M(η(5)-C(5)Me(5))Cl(LEV-ppy)] (M = Rh (1) and Ir (2)) bearing the lipophilic levonorgestrel group 17-α-[2-phenylpyridyl-4-ethynyl]-19-nortestosterone (LEV-ppy), where the chelating ligand is N and C-bound, have been prepared and characterized. Both compounds are more active than cisplatin (about 6-fold) in T47D (breast cancer) at 48 h incubation time. On the other hand, very low resistance factors (RF) of 1 and 2 in A2780cisR (cisplatin-resistant ovarian carcinoma) at 48 h were observed (RF = 0.9 and 1.1, respectively). The iridium steroidal compound 2 is twice as active as the non-steroidal analogue 2', whose promising anticancer activity has recently been reported by Sadler. Theoretical DFT calculations on complexes 1 and 2 at the B3LYP-D/def2-TZVP-ecp level of theory show that the strongest bond to the metal atom is the η(5)-interaction to the Cp* ligand and that both of them feature a rather strong metal-chlorine bond. The new steroidal conjugates 1 and 2 are able to bind to DNA according to Hoechst 33258 displacement experiments and ESI-TOF MS spectrometry studies. Complexes 1 and 2 are also cathepsin B inhibitors, an enzyme implicated in a number of cancer related events.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Agents / chemistry*
  • Antineoplastic Agents / pharmacology
  • Binding, Competitive
  • Cathepsin B / antagonists & inhibitors
  • Cathepsin B / metabolism
  • Cell Line, Tumor
  • Cell Survival / drug effects
  • DNA / metabolism
  • Humans
  • Iridium / chemistry*
  • Iridium / pharmacology
  • Levonorgestrel / chemistry*
  • Levonorgestrel / pharmacology
  • Organometallic Compounds / chemistry*
  • Organometallic Compounds / pharmacology
  • Rhodium / chemistry*
  • Rhodium / pharmacology

Substances

  • Antineoplastic Agents
  • Organometallic Compounds
  • Iridium
  • Levonorgestrel
  • DNA
  • Rhodium
  • Cathepsin B