Molecular basis for resistance to the anticancer drug cisplatin in Dictyostelium The GenBank accession numbers for the sequences reported in this paper are AF233610 (S-1-P lyase), AF233612 (PIP5K), AF233611 (P2Y purine receptor 1), AF233613 (CAAX prenyl protease) and AF233614 (unidentified gene).

Abstract

The efficacy of the widely used chemotherapeutic drug cisplatin is limited by the occurrence of drug-resistant tumour cells. To fully exploit the potential of this drug in cancer therapy, it is imperative to understand the molecular basis of cisplatin resistance. Using an insertional mutagenesis technique in cells of Dictyostelium discoideum, we have identified six genes which are involved in cisplatin resistance. None of these genes has been previously linked to resistance to this drug. Several of these genes encode proteins that are involved in signal transduction pathways which regulate cell death, cell proliferation or gene regulation. The resistance of these mutant strains is specific for cisplatin, since deletion of these genes does not confer resistance to other DNA-damaging agents. Significantly, the disruption of three of these genes, encoding the sphingosine-1-phosphate lyase, the RegA cAMP phosphodiesterase and a phosphatidylinositol-4-phosphate 5-kinase, also results in abnormalities in the multicellular development of this organism, although there is no change in the rate of mitotic cell growth. This study has identified previously unsuspected molecular pathways which function in the cellular response to cisplatin and are required for normal morphogenesis, and underscores the complexity of the cellular response to cisplatin. These pathways provide potential targets for modulating the response to this important drug.

Initiation of Mucin-type O-Glycosylation in Dictyostelium Is Homologous to the Corresponding Step in Animals and Is Important for Spore Coat Function

“…The upstream region, presumably containing expression regulatory elements, was confirmed by PCR amplification using fp1 and rp1 and partial sequencing. cis4c was previously shown by Northern blot analysis to be expressed throughout the life cycle (27).…”

“…A cloned ClaI-ClaI fragment of Dictyostelium gDNA, known as cis4c, was found that had been isolated in a screen for genes that when disrupted resulted in increased resistance to the drug cisplatin (27). The sequence comprised a single long ORF, which conceptually encodes a polypeptide sequence that includes a 284-amino acid stretch with 29% identity and 52% similarity to that of the apparent catalytic domain of pp ␣-GlcNAc-T1 (Fig.…”

“…Binding of mAb 54.2 is reduced or eliminated in strains containing mutant alleles of the modB locus, resulting in increased mobility of SP29 and SP85 during SDS-PAGE (17,30). In the cisplatinresistant strain that originally defined the cis4c(gntB) locus (27), the coding region for the predicted catalytic domain is interrupted by a bsr resistance cassette ( Fig. 2A).…”

“…HW11 is an axenic strain that carries a modB mutant allele, which appears to partially retain function (29). Cis4c is a cisplatin-resistant strain (27) that contains an insertion of the bsr Ϫ marker in the cis4c(gntB) gene described in this report. This gene was originally described as having similarity to the kinase domain of a putative phosphatidylinositol 4-phosphate 5-kinase from Arabidopsis.…”

“…1 and 2A) had been cloned previously (27). Nucleotide sequences from this fragment were used to query data bases containing sequences from shotguncloned Dictyostelium gDNA fragment for overlapping sequences, accessible via the DictyBase World Wide Web Server (dictybase.org/dicty.…”