PM00104 is a new synthetic marine-derived compound currently in Phase I clinical development for the treatment of solid tumors. The compound has a reactive carbinolamine group that can establish a covalent bond with the exocyclic amine group of guanines located in the minor groove of the DNA. This adduct is additionally stabilized through the establishment van der Waals interactions and one or more hydrogen bonds with adjacent nucleotides in the opposite strand, generating a structure that resembles a DNA interstrand crosslink. First we characterized the cytotoxic effect of PM00104 on a 24 cell lines panel, representing eleven relevant types of human cancer. The mean GI50 value for the panel was 4.8 nM. The compound exhibits higher cytotoxic activity against leukemia and stomach tumor cell lines. We clustered the panel cell lines into two groups depending on their p53 status: wild-type p53 (n=9) and mutant or null p53 (n=14), according to the information contained in the Sanger Database. Mean GI50 for wild-type p53 cell lines was 8 nM; mean GI50 for mutant or null p53 cell lines was 2 nM. The difference in GI50 between both groups was statistically significant (p=0.035; one-tailed Student\#8217;s t unpaired test). PM00104was able to bind both unmethylated and methylated DNA, as demonstrated through in vitro gel-shift assays. PM00104-DNA adducts eventually gave rise to double strand breaks, which we observed through the appearance of \#947;-H2AX foci as surrogate marker. Treatment with the compound also triggered accumulation of the cells in the S-phase of the cell cycle. Since double strand breaks are repaired by homologous recombination and non homologous end joining mechanisms, accumulation of such DNA damage can lead to aberrant chromosome joining, giving rise to mitotic catastrophe. In fact, p53-/- HCT116 cells were more sensitive to PM00104 than wild type HCT116 cells, and more prone to suffer mitotic catastrophe after the long term treatment with sub-GI50 concentrations of the drug. At higher concentrations (15 nM), PM00104 induced higher levels of PARP cleavage in p53-/- HCT116 than in wild type HCT116. The data presented in this work support the importance of p53 status on the effect that PM00104 exerts on human cancer cell lines at pharmacologically meaningful concentrations.

Citation Information: In: Proc Am Assoc Cancer Res; 2009 Apr 18-22; Denver, CO. Philadelphia (PA): AACR; 2009. Abstract nr 4527.

100th AACR Annual Meeting-- Apr 18-22, 2009; Denver, CO

American Association for Cancer Research
2009