Serum p53 antibodies in correlation to other biological parameters of breast cancer.

Breast cancer is the second most frequent cancer of Thai women. Mutation of p53 is a common event in breast cancer. This alteration can result in cellular accumulation of p53 and may also found in serum p53 antibodies (p53-Abs). To clarify prognostic significance of these antibodies, we evaluated p53-Abs in 158 sera of patients with breast cancer. Thirty (19%) patients were found to have p53-Abs. The incidence of p53-Abs tended to be higher in patients with advanced disease group (stages III and IV) than patients with early disease group (stages I and II) (P=0.055). Strong correlations were found between the presence of p53-Abs and p53 protein expression (P<0.001) and lymph node status (P=0.021). The presence of p53-Abs was associated with lack of estrogen (ER) receptor expression (P=0.035) but was not related to progesterone receptor (PR) (P=0.567). In addition, there was a statistically significant correlation between p53-Abs and proliferation associated antigen Ki-67 (P=0.006), but no relation between c-erbB2 oncoprotein and p53-Abs was observed (P=0.112). Additionally, no correlation was noted between the presence of p53-Abs and serum carcinoembryonic antigen (CEA) or carbohydrate antigen (CA15-3). Our findings indicate that p53-Abs appears to be a promising new parameter to evaluate the cellular biology and prognosis of breast cancer.

Taxol resistance.

BACKGROUND: Taxol has gained considerable attention in cancer therapy in recent years and is successfully used in treating a variety of tumors, including those of the breast, ovary and lung. Despite its preclinical and clinical success, the ability of tumors to develop an acquired resistance to drugs used for treatment remains a major obstacle to cancer cure. A better understanding of the various mechanisms of Taxol resistance may have important implications for strategies designed for cancer treatment. METHOD: This review summarizes the information available to date concerning the effects of Taxol and the development of drug resistance, focusing particularly on alterations in microtubules. RESULTS AND DISCUSSION: Acquired resistance to Taxol is a function of multiple adaptations. Although the cellular transport of Taxol appears to be an important mechanism of resistance to Taxol, altered transcription and posttranslational modification of microtubular changes may be involved in the mechanism of drug resistance.

Different microtubule network alterations induced by pachymatismin, a new marine glycoprotein, on two prostatic cell lines.

Pachymatismin is a new cytostatic factor extracted from the marine sponge Pachymatisma johnstonii Bowerbank. To investigate the mechanism of action of pachymatismin, we studied its effects on two human prostate cell lines (DU145 and E4) of tumor origin. Immunocytochemistry demonstrated that the drug caused depolymerization of microtubules in DU145 cells, this effect being similar to that of estramustine, known to be a microtubule-depolymerizing agent. E4 cells, described to be resistant to the microtubule-depolymerizing agent estramustine, were also found resistant to pachymatismin. Pachymatismin at the same dose that destroys microtubule organization in DU145 cells is not able to induce microtubule depolymerization in E4 cells. Compared to the estramustine- and pachymatismin-sensitive DU145 cells, E4 cells revealed an increase of betaI+II, betaIII, betaIV isotypes as well as post-translational modifications of tubulin, such as polyglutamylation and acetylation. In addition, the level of tau protein was also enhanced in E4 cells compared to DU145 cells. The effects of pachymatismin were tested in vitro using calf brain microtubules. It was shown that the drug lowers the capacity of microtubules to reassemble in vitro. Interestingly, pachymatismin has been found to inhibit microtubule assembly less efficiently when the ratio of tau to tubulin is increased. Taken together, pachymastismin has been shown to induce in vivo microtubule depolymerization following binding to microtubule proteins. Changes in microtubule components such as tubulin isoforms or tau may be involved in a decrease of sensitivity to pachymatismin.

Estramustine resistance.

Estramustine (EM), a conjugate of nornitrogen mustard and estradiol, is a antimicrotubule drug currently in use for the treatment of advanced prostatic carcinoma. Experimental data are accumulating concerning the antitumor effect of EM in other malignancies, and clinical studies in other malignancies are ongoing. This review summarizes the information available to date concerning the effects of EM and the development of drug resistance. EM depolymerizes microtubules by binding to microtubule-associated proteins (MAPs) as well as tubulin. Because of the radiosensitizing effect of this drug there has been a recent increase in interest concerning estramustine and its clinical use. Recently, it was proposed that EM induces an apoptotic cell death in glioma cells in vitro and in a rat model. EM resistance is distinct from MDR phenotype; it has been used in combination with antimitotic agents which are part of the MDR phenotype. Observations made with estramustine-resistant cell lines show the acquisition of estramustine resistance is a function of multiple adaptation by changes at tubulin expression pattern, and is also associated with changes in tau expression and phosphorylation.

Estramustine resistance correlates with tau over-expression in human prostatic carcinoma cells.

Estramustine (EM) is an anti-microtubule drug used in the treatment of hormone-refractory advanced prostate cancer. Since microtubules are the targets for EM cytotoxicity, we investigated the effects of EM on the microtubule-associated protein tau to determine what role it may play in drug resistance. We have compared tau expression in human prostate cancer cells (DU145) and an EM-resistant derived cell line (E4). Reverse transcriptase polymerase chain reaction has established that tau is expressed in both cell lines but increased 1.9-fold in E4 compared with DU145 cells. This result was confirmed at the protein level by Western blotting. Tau is a phosphoprotein, most of its reported phosphorylation sites being serine or threonine residues. We have shown, however, that tau is also phosphorylated at tyrosine residues in DU145 cells and that the phosphotyrosine level of tau is significantly increased in E4 cells. Moreover, DU145 cells exposed to short term micromolar drug concentrations enter a phase of microtubule depolymerization, display an increased level of tau phosphorylation and follow a pattern similar to that observed in EM-resistant E4 cells. EM is therefore able to induce a very rapid change in the posttranslational state of tau. Our results show that the acquisition of EM resistance in E4 cells, which is accompanied by changes at the tubulin level, is also associated with important changes in tau expression and phosphorylation.

Association of estramustine resistance in human prostatic carcinoma cells with modified patterns of tubulin expression.

Estramustine (EM) is an antimicrotubule drug used in the treatment of hormone refractory advanced prostate cancer. To investigate the mechanism of resistance to EM, we compared its effects on human prostate cancer cells (DU145) and an estramustine-resistant derived cell line (E4). Immunofluorescence demonstrated that EM caused depolymerization of microtubules and blocked cells in mitosis in DU145 cells, with less effect in E4 cells. Using tubulin isotype-specific antibodies, a threefold increase in betaIII and approximately twofold increase in betaI + II isotype in E4 cells compared to DU145 cells were observed. A most interesting observation concerned an increase in the posttranslational modification of alpha-tubulin of both polyglutamylation and acetylation in the E4 cells. Significant to this observation, using direct EM photoaffinity labeling of tubulin, drug binding to the most acidic posttranslationally modified forms of alpha-tubulin was shown to be minimal. Taken together, these results indicate that the modification of the tubulin expression pattern may be responsible for estramustine resistance by both lowering the amount of drug bound to microtubules and inducing more stable microtubules.

Biodistribution of iodine-125 tyramine transforming growth factor alpha antisense oligonucleotide in athymic mice with a human mammary tumour xenograft following intratumoral injection.

The Watson-Crick base pairing rule provides the underlying principle for the antisense (AS) approach to inhibiting gene expression. Transforming growth factor alpha (TGFalpha) was the first growth factor to be associated with tumorigenesis, thus making the TGFalpha (mRNA) a potential target for AS therapy and offering the potential for monitoring of the progression of malignancy by non-invasive imaging with radiolabelled AS phosphodiester. Probe labelling and biodistribution were studied in the present report. A 23-mer oligonucleotide sequence was synthesized and grafted in 5' with a tyramine group which was further radioiodinated. The radiolabelled AS was injected intratumorally in mammary tumour-bearing BALB/c mice (3 weeks after inoculation of 7.10(6)NS2T2A mammary cells). Biodistribution was monitored by sequential scintigraphy and organ radioactivity after autopsy. The 5' tyramine group allowed specific and stable radiolabelling of the AS with 125I. The 125I AS oligonucleotide was rapidly cleared from the tumour by intestine and kidneys. Four hours after intratumoral injection, 6.5%+/-1.5% of the dose was retained in the tumour as non-degraded 125I AS. It is concluded that 5' tyraminylated AS provides information on the biodistribution of AS oligonucleotide following intratumoral injection. These data will contribute to the pharmacology of AS oligonucleotides which can be used for therapy.