Unfaithfulness and promiscuity of a mutant androgen receptor in a hormone-refractory prostate cancer

Missense mutations in the androgen receptor (AR) contribute to the failure of hormonal therapy for prostate cancer (PCa), but the underlying molecular bases remain uncharacterized. Here, we describe a new AR variant found in a hormone-refractory metastatic PCa, in which threonine 575 in the DNA binding domain, and threonine 877 in the ligand-binding domain, were both replaced by an alanine. Using gene reporter assays, we demonstrate that the T575A mutation weakened transcriptional activity from promoters containing AR-specific responsive elements, while activity from promoters with AR-non-specific elements was enhanced. Data from gel shift experiments revealed a preferential binding of the T575A mutant to AR-non-specific motifs. We demonstrate that the two mutations T575A and T877A cooperate to confer new functional properties on the AR, and that the mutant AR functions simultaneously as a promiscuous AR due to the T877A mutation, and an unfaithful AR due to the T575A mutation.

Cisplatin-induced genes as potential markers for thyroid cancer

Despite the uncontested role of p53 in cycle arrest/cell death after cisplatin treatment, to date the question whether wild-type p53 confers a resistant or sensitive status on the cell is still a matter of debate. Isogenic and isophenotypic human thyroid papillary carcinoma cell line variants for p53 differently expressed cycle genes after cisplatin treatment. Seven genes (CDC6-related protein, CCNC, GAS1, TFDP2, MAPK10/JNK3, WEE1, RPA1) selected after expression on an Atlas human cell cycle array were analyzed by quantitative real-time PCR. While cisplatin treatment increased their expression in p53 wild-type cells it decreased it in cells with inactivated p53 and had no or less effect on cells with mutated p53. These results show that in a well-defined system, different alterations of p53 can lead to a different regulation of genes and hence to either resistance or sensitivity to cisplatin. Moreover for the first time, MAPK10/JNK3 was identified in human thyroid cells and tissue. Four of the genes (CDC6-related protein, CCNC, GAS1 and TFDP2) were decreased in human papillary carcinoma tissues. Relevance of these genes (especially a decrease in GAS1 in thyroid papillary carcinoma) in various malignant pathologies has already been shown. These genes may be explored as new markers in advanced thyroid cancer such as metastatic and anaplastic forms displaying p53 alterations.

Conflicting effects of caffeine on apoptosis and clonogenic survival of human K1 thyroid carcinoma cell lines with different p53 status after exposure to cisplatin or UVc irradiation

Caffeine has been widely described as a chemo/radiosensitizing agent, presumably by inhibiting DNA repair, and affecting preferentially cells with an altered p53 status. We evaluated the effects of caffeine using isogenic and isophenotypic K1 cells derived from a papillary thyroid carcinoma and displaying either a wild type or a mutated p53 status. Apoptosis and clonogenic survival were examined after exposure of the cells to cisplatin or UVc irradiation. We find that at the most currently used concentration, 2mM, caffeine hinders cisplatin or UVc induced apoptosis in K1 cells. In addition, at this already barely achievable concentration in vivo, caffeine does not decrease their clonogenic survival. Hence in our cellular model, caffeine does not behave as a chemo- or a radiosensitizer. Although surprising, these results (1) are in agreement with the delayed G2/M block caused by caffeine that we previously observed in normal human fibroblasts and K1 cells and (2) allow us to elucidate some discrepancies concerning this molecule throughout the literature such as increase or decrease of apoptosis and clonogenic survival, activation or deactivation of molecules involved in DNA damage repair and proliferation inhibition but accelerated G2/M traverse.