Castration resistance in prostate cancer (PCa) constitutes an advanced, aggressive disease with poor prognosis, associated with uncontrolled cell proliferation, resistance to apoptosis, and enhanced invasive potential. The molecular mechanisms involved in the transition of PCa to castration resistance are obscure. Here, we report that the nonselective cationic channel transient receptor potential vanilloid 2 (TRPV2) is a distinctive feature of castration-resistant PCa. TRPV2 transcript levels were higher in patients with metastatic cancer (stage M1) compared with primary solid tumors (stages T2a and T2b). Previous studies of the TRPV2 channel indicated that it is primarily involved in cancer cell migration and not in cell growth. Introducing TRPV2 into androgen-dependent LNCaP cells enhanced cell migration along with expression of invasion markers matrix metalloproteinase (MMP) 9 and cathepsin B. Consistent with the likelihood that TRPV2 may affect cancer cell aggressiveness by influencing basal intracellular calcium levels, small interfering RNA-mediated silencing of TRPV2 reduced the growth and invasive properties of PC3 prostate tumors established in nude mice xenografts, and diminished expression of invasive enzymes MMP2, MMP9, and cathepsin B. Our findings establish a role for TRPV2 in PCa progression to the aggressive castration-resistant stage, prompting evaluation of TRPV2 as a potential prognostic marker and therapeutic target in the setting of advanced PCa. Cancer Res; 70(3); 1225-35. ©2010 AACR.

Two isoforms of the dopamine D2 receptor have been characterized, D2L (long) and D2S (short), generated by alternative splicing from the same gene. They differ by an in-frame insert of 29 amino acids specific to D2L within the putative third intracytoplasmic loop of the receptor. We have previously demonstrated (Montmayeur, J.-P., Guiramand, J., and Borelli, E. (1993) Mol. Endocrinol. 7, 161-170) that D2S and D2L, although presenting very similar pharmacological profiles, couple differently to the alpha-subunit of guanine nucleotide-binding regulatory proteins (G-proteins). In particular, D2L, but not D2S, requires the presence of the alpha-subunit of the inhibitory G-protein (G alpha i2) to elicit greater inhibition of adenylyl cyclase activity. The insert present in D2L must therefore confer the specificity of interaction with G alpha i2. Thus, we introduced substitution mutations within the D2L insert. These mutant receptors were expressed in JEG3 cells, a G alpha i2-deficient cell line, scoring for those presenting an increased inhibition of adenylyl cyclase by dopamine. Our analysis identified two mutants, S259/262A and D249V, with these properties. These results clearly show that the insert present in D2L plays a critical role in the selectivity for the G-proteins interacting with the receptor.

Androgen receptor (AR) mutations that modify both the ligand binding and the transactivation capacities of the AR represent one of the mechanisms involved in the transition of prostate cancer (PCa) from androgen-dependent to androgen-independent growth. We use a yeast-based functional assay to detect and analyze mutant ARs in PCa. We report the detection of 2 different mutant ARs within the same metastatic tumour sample harvested in a patient with advanced PCa who had escaped androgen deprivation. Concomitantly to the widely described T877A mutant AR, we identified an additional double mutant AR harboring the nonsense mutation Q640Stop just downstream the DNA binding domain together with the T877A point mutation. This type of mutation, which leads to a c-terminal truncated AR, has not been described yet in PCa. Using luciferase reporter assays we demonstrated that this truncated AR exhibited constitutive transactivation properties. In conclusion, our data suggest that mutation-induced constitutive activation of the AR could be a mechanism used by PCa cells to escape androgen deprivation. © 2003 Wiley-Liss, Inc. Key words: androgen receptor mutations; prostate cancer; androgen independence; constitutive transactivationProstate cancer (PCa) is the most frequently diagnosed malignancy in men and the second leading cause of cancer deaths in Western countries. As prostate cancer growth depends on androgens, the standard first line therapy for advanced PCa consists of decreasing the plasma concentration of testicular testosterone by medical or surgical castration. 1,2 This androgen ablation therapy is eventually combined to anti-androgens to further block the effects of androgens produced from adrenal precursors. The response to such androgen ablation is high and provides subjective relief to more than 80% of patients. Unfortunately, the benefit of this therapy is only transitory lasting some months or years, with a median duration of 12-18 months, and all patients will eventually relapse with tumour cells whose growth escapes the androgen deprivation. Although these relapsed tumours are clinically androgen-independent, many lines of evidence indicate that the androgen receptor (AR) signaling pathway remains active and may contribute to the escape to androgen ablation. 3 In this regard, the amplification and the overexpression of the AR gene or the stabilization of the AR may allow PCa cells to continue androgendependent growth even in very low levels of androgens left in serum after castration. 4 -6 Also, the cross-talk with the mitogenactivated protein kinase (MAPK) or the Akt/protein kinase B phosphorylation pathways 7 and the altered expression of AR coactivator proteins 8 may lead to the activation of AR in a ligandindependent manner. Finally, mutations in the ligand binding domain of the AR that expand the specificity or the affinity of the receptor to other hormones may allow it to respond to different steroids as well as anti-androgens. 9 We have described previously a yeast-based functional assay to simultane...