Background: Protein expression profiling for differences indicative of early cancer has promise for improving diagnostics. This report describes the first stage of a National Cancer Institute/Early Detection Research Network-sponsored multiinstitutional evaluation and validation of this approach for detection of prostate cancer. Methods: Two sequential experimental phases were conducted to establish interlaboratory calibration and standardization of the surface-enhanced laser desorption (SELDI) instrumental and assay platform output.

Two paclitaxel(Ptx)-resistant ovarian cancer cell lines, 1A9/Ptx-10 and 1A9/Ptx-22, isolated from the 1A9 cell line (a clone of the A2780 line) by continuous exposure to Ptx and verapamil, have point mutations in their major b-tubulin gene and in one or both alleles of their TP53 gene. These cells were examined for alterations in cell cycle regulators and the tubulin-binding protein stathmin. Unlike parental cells, neither 1A9/Ptx-10 nor 1A9/Ptx-22 expressed detectable levels of p21 WAF1/Cip1 , a putative transcriptional regulator of stathmin, but did overexpress stathmin and Bcl2. No differences were noted in the expression levels of proliferative cell nuclear antigen or tyrosine-phosphorylated p34 Cdc2 . Ptx treatment altered little the expression of stathmin in the parental cell line, although it increased p21 WAF1/Cip1 levels several-fold. Infection of Ptx-resistant lines with a wild-type TP53-bearing adenovirus (AdWTp53) changed cell cycle distribution and increased the levels of p21 WAF1/Cip1 , but caused no changes in stathmin levels. Microtubule drug resistance in ovarian carcinoma may be associated with altered p53/21 WAF1/Cip1 regulatory pathways for stathmin expression and function.

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(+)‐Discodermolide is a sponge‐derived natural product with the most potent microtubule stabilizing activity yet discovered. Its actions parallel that of the promising antibreast cancer agent paclitaxel despite the lack of any apparent similarities in the drugs' structures. To complement our previous studies on human breast cancer cells, we compared the effects of the two drugs against the estrogen receptor positive but tamoxifen‐resistant MCF‐7/LY2 line. Growth inhibition, cell, and nuclear morphological, electrophoretic, and flow cytometric analyses were performed. (+)‐Discodermolide potently inhibited the growth of the cells (e.g., 48‐hours IC50 of 1.5 nM) at concentrations similar to those observed with paclitaxel, and somewhat lower than the values observed previously with estrogen responsive MCF‐7 cells and estrogen nonresponsive MDA‐MB231 cells. (+)‐Discodermolide‐treated MCF‐7/LY2 cells had condensed and highly fragmented nuclei, as well as micronuclei, suggesting mitotic block and the induction of apoptosis. Flow cytometric comparison of cells treated with either drug at 10 nM showed both caused accumulation into the G2/M portion of the cell cycle as well as induction of a pronounced hypodiploid cell population, with (+)‐discodermolide yielding a greater effect. The timing and type of high molecular weight DNA fragmentation induced by the two agents was fully consistent with induction of apoptosis, again with (+)‐discodermolide showing an advantage over paclitaxel in this regard. More extensive DNA fragmentation was noted in MCF‐7/LY2 than has been observed in MCF‐7 and MDA‐MB231 cells. These in vitro results, coupled with those obtained previously, suggest that (+)‐discodermolide might have promise as a new chemotherpeutic agent against breast cancers. In addition, its novel and synthetically approachable structure make (+)‐discodermolide a promising lead compound for design and discovery of new microtubule stabilizing agents as alternatives to taxoids.

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