Identification of Griseofulvin as an Inhibitor of Centrosomal Clustering in a Phenotype-Based Screen

Abstract

A major drawback of cancer chemotherapy is the lack of tumor-specific targets which would allow for the selective eradication of malignant cells without affecting healthy tissues. In contrast with normal cells, most tumor cells contain multiple centrosomes, associated with the formation of multipolar mitotic spindles and chromosome segregation defects. Many tumor cells regain mitotic stability after clonal selection by the coalescence of multiple centrosomes into two functional spindle poles. To overcome the limitations of current cancer treatments, we have developed a cell-based screening strategy to identify small molecules that inhibit centrosomal clustering and thus force tumor cells with supernumerary centrosomes to undergo multipolar mitoses, and subsequently, apoptosis. Using a chemotaxonomic selection of fungi from a large culture collection, a relatively small but diverse natural product extract library was generated. Screening of this compound library led to the identification of griseofulvin, which induced multipolar spindles by inhibition of centrosome coalescence, mitotic arrest, and subsequent cell death in tumor cell lines but not in diploid fibroblasts and keratinocytes with a normal centrosome content. The inhibition of centrosome clustering by griseofulvin was not restricted to mitotic cells but did occur during interphase as well. Whereas the formation of multipolar spindles was dyneinindependent, depolymerization of interphase microtubules seemed to be mechanistically involved in centrosomal declustering. In summary, by taking advantage of the tumorspecific phenotype of centrosomal clustering, we have developed a screening strategy that might lead to the identification of drugs which selectively target tumor cells and spare healthy tissues. [Cancer Res 2007;67(13):6342-50]

Kinetic stabilization of microtubule dynamic instability by benomyl increases the nuclear transport of p53

“…Recent studies indicate that the antifungal drug griseofulvin has the potential to be used as an anticancer drug [25][26][27]. The discoveries that benomyl suppresses microtubule dynamics at its lower effective inhibitory concentration and increases the nuclear accumulation of p53 will be helpful to explore the anticancer potential of benomyl and its metabolite carbendazim.…”

“…Recently, the antifungal drug griseofulvin is gaining importance because of its low toxicity and its ability to inhibit the proliferation of cancer cells similar to other potential anticancer drugs [25][26][27]. Rebacz et al have shown that griseofulvin specifically targeted tumor cells and inhibited their proliferation without having much effect on normal cells [27].…”

“…Rebacz et al have shown that griseofulvin specifically targeted tumor cells and inhibited their proliferation without having much effect on normal cells [27]. In addition, carbendazim the active metabolite of benomyl [1,13,14], is presently undergoing clinical trials for the treatment of advanced solid tumors (ClinicalTrials.gov Identifier: NCT00023816, NCT00003709); hence, understanding the mechanism of action of benomyl is also of clinical importance.…”

A Mild Method for Regioselective Labeling of Aromatics with Radioactive Iodine

“…Our interest in iodination techniques arose during our search for potent analogues of the natural product griseofulvin (1) [10] that can inhibit centrosomal clustering in cancer cells. [11] GF-15 (compound 2, Figure 1) was identified as one of the most active analogues, [12] and for in vivo biodistribution and half-life studies we became interested in 125 I labeling of 2. [13] As the activities of the three iodinated isomers of 2 (i.e., 8-10, see Scheme 1) in a phenotypic whole-cell assay for multipolarity [11] are markedly different (data not shown), we found it crucial to apply a method that would afford a single regioisomer and thus enable us to access the ortho-(i.e., 8), meta-(i.e., 9), and paraiodo (i.e., 10) isomers.…”

“…[11] GF-15 (compound 2, Figure 1) was identified as one of the most active analogues, [12] and for in vivo biodistribution and half-life studies we became interested in 125 I labeling of 2. [13] As the activities of the three iodinated isomers of 2 (i.e., 8-10, see Scheme 1) in a phenotypic whole-cell assay for multipolarity [11] are markedly different (data not shown), we found it crucial to apply a method that would afford a single regioisomer and thus enable us to access the ortho-(i.e., 8), meta-(i.e., 9), and paraiodo (i.e., 10) isomers. McKillop et al [14] have introduced a method for the iodination of small aryl-containing organic molecules by the use of Tl(OCOCF 3 ) 3 and iodide.…”