Targeting the multidrug transporter Patched potentiates chemotherapy efficiency on adrenocortical carcinoma in vitro and in vivo.

One of the crucial challenges in the clinical management of cancer is the resistance to chemotherapeutics. We recently demonstrated that the Hedgehog receptor Patched, which is overexpressed in many recurrent and metastatic cancers, is a multidrug transporter for chemotherapeutic agents such as doxorubicin. The present work provides evidences that Patched is expressed in adrenocortical carcinoma (ACC) patients, and is a major player of the doxorubicin efflux and the doxorubicin resistance in the human ACC cell line H295R. We discovered that methiothepin inhibits the doxorubicin efflux activity of Patched. This drug-like molecule enhances the cytotoxic, pro-apoptotic, antiproliferative and anticlonogenic effects of doxorubicin on ACC cells which endogenously overexpress Patched, and thereby mitigates the resistance of these cancer cells to doxorubicin. Moreover, we report that in mice the combination of methiothepin with doxorubicin prevents the development of xenografted ACC tumors more efficiently than doxorubicin alone by enhancing the accumulation of doxorubicin specifically in tumors without obvious undesirable side effects. Our results suggest that the use of an inhibitor of Patched drug efflux such as methiothepin in combination with doxorubicin could be a promising therapeutic option for adrenocortical carcinoma, and most likely also for other Patched-expressing cancers.

Involvement of serotonin 5HT1 and 5HT2 receptors and nitric oxide synthase in the medial preoptic area on gonadotropin secretion.

Due to the stimulatory action of serotonin (5HT) and nitric oxide (NO) on the secretion of gonadotropins and PRL, this work aimed at investigating the participation of serotoninergic receptors 5HT(1) and 5HT(2) of the medial preoptic area (MPOA) in the control of luteinizing hormone (LH), follicle stimulating hormone (FSH) and prolactin (PRL) secretion and the possible modulation by ovarian steroids as well as the possible participation of NO as a mediator of the stimulatory effects of serotonin in the MPOA on LH secretion. Microinjections of three different doses (0.02, 0.2, and 2 ug) of methiothepin, a serotoninergic 5HT(1) antagonist or ketanserin, a seretoninergic 5HT(2) antagonist, were carried out into the MPOA in ovariectomized rats treated or not with estrogen or estrogen plus progesterone. Other groups of ovariectomized rats treated with estrogen, estrogen plus progesterone or vehicle were prepared to evaluate NOS activity in the MPOA. Plasma LH, FSH, and PRL in ovariectomized rats were not altered by the microinjection of methiothepin or ketanserin in the MPOA. Methiothepin microinjection in the MPOA reduced LH but did not change plasma FSH and PRL in ovariectomized rats treated with estrogen or estrogen plus progesterone. On the other hand, ketanserin microinjection in the MPOA reduced plasma LH and FSH but did not change plasma PRL in the animals submitted to the same steroidal treatment. NOS activity in the MPOA was significantly reduced by methiothepin or ketanserin in ovariectomized rats treated with estrogen or estrogen plus progesterone. In conclusion, this work showed that in the studied conditions, serotonin in the MPOA: (1) does not work in the control of PRL secretion through 5HT(1) and 5HT(2) receptors; (2) integrates the control of FSH secretion by 5HT(2) receptors, but not 5HT(1); (3) in the presence of estrogen, stimulates LH secretion by 5HT(1) and 5HT(2) receptors, which can be differentially modulated by progesterone; (4) at least partly, stimulates LH secretion by nitric oxide activity.

Adenosine diphosphate potentiates the inhibition of norepinephrine-induced relaxation by 5-hydroxytryptamine in canine coronary arteries.

Vasoactive substances released from aggregating platelets inhibit beta-adrenergic neurotransmission in coronary arteries. Studies were carried out on the effects of two such vasoactive substances on canine coronary arteries, at concentrations equivalent to that released by platelets under physiological conditions. 5-Hydroxytryptamine (5 X 10(-7) M) reduced the sensitivity of coronary artery ring segments to the beta-adrenergic relaxing effects of norepinephrine. Adenosine diphosphate (3 X 10(-6) M) further reduced the sensitivity to norepinephrine caused by 5-hydroxytryptamine, while the nucleotide alone had no significant effect. 5-Hydroxytryptamine and adenosine diphosphate acted selectively on the norepinephrine-induced relaxation; whereas the relaxatory response of the vessel to nitroprusside, a direct muscle relaxant, was unaffected. 5-Hydroxytryptamine caused contraction of the tissue, but this opposing response did not account for the inhibition of the norepinephrine-induced relaxation observed in the presence of the indoleamine. The decreases in sensitivity to norepinephrine caused by 5-hydroxytryptamine and adenosine diphosphate were prevented by the serotonin receptor antagonist, methiothepin. The potentiation by adenosine diphosphate of the 5-hydroxytryptamine-induced shift in the relaxation caused by norepinephrine was blocked by the purine receptor antagonist, 8-(p-sulfophenyl)-theophylline. Neither adenosine nor alpha,beta-methylene adenosine diphosphate potentiated the action of 5-hydroxytryptamine, suggesting that phosphate hydrolysis of the nucleotide is required for the action of adenosine diphosphate. These results suggest that adenosine diphosphate potentiates the inhibitory effect of 5-hydroxytryptamine on the beta-adrenergic response of coronary arteries exposed to vasoactive substances released from platelets.