Jianning Xu

Earlier studies showed that melatonin reduced the growth of 17-beta-estradiol (E(2))-induced rat pituitary prolactin-secreting tumor (prolactinoma) in vivo. The mechanisms of melatonin's inhibitory action on the prolactin-secreting tumor were further explored by investigating the in vitro effects of melatonin on the growth of pituitary prolactin-secreting tumor cells. Primary cultured prolactinoma cells from E(2)-induced rat pituitary prolactin-secreting tumor were treated with 10(-5), 10(-4) or 10(-3) m melatonin for 5 days. Apoptosis was evaluated using flow cytometry and the TdT-mediated dUTP nick-end labeling (TUNEL) method. In addition, cell viability was analyzed by (3,4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. It was found that incubation of prolactinoma cells with 10(-5), 10(-4) or 10(-3) m melatonin for 5 days inhibited cell growth and increased cell apoptosis. Furthermore, melatonin increased caspase-3 activity, Bax mRNA expression, and cytochrome c protein expression. Conversely, Bcl-2 mRNA expression and mitochondrial membrane potential were inhibited by melatonin treatment. Our results further suggest that melatonin inhibits tumor growth by inducing apoptosis of rat pituitary prolactin-secreting tumor directly via the damage of mitochondria.

Abstract Purpose: Genomic alterations in key components of PI3K/mTOR pathway have been proposed as candidate predictive markers for rapalog therapy in renal cell carcinoma (RCC). We tested this hypothesis in patients from a randomized phase II trial of everolimus versus sunitinib. Patients and Methods: Archival specimens collected at baseline were analyzed with targeted next-generation sequencing (NGS). Focus of interest were alterations in key PI3K pathway components. PTEN expression was assessed by IHC. Association between molecular findings and treatment outcomes was investigated; same associations were tested for 2 everolimus-treated trial cohorts in gastric and hepatocellular carcinoma (HCC). Results: Among 184 everolimus-treated patients with RCC with NGS data, mutation rates in genes of interest were 6% (TSC1), 4.4% (TSC2), and 8.2% (mTOR); 44% harbored alterations in ≥1 PI3K pathway component. For subjects with presence versus absence of mutations in TSC1, TSC2, or mTOR progression-free survival (PFS) neither differed on univariate analysis (HR, 1.0; P = 0.895) nor on multivariate testing stratified by MSKCC risk group and other established prognostic factors (HR, 1.1; P = 0.806). Everolimus-treated patients with retained (n = 50) versus lost (n = 50) PTEN IHC expression had median PFS of 5.3 months versus 10.5 months (HR, 2.5; P < 0.001). Such differences were not seen with sunitinib (10.9 months vs. 10.3 months; HR, 0.8; P = 0.475). Molecular findings did not correlate with outcomes in gastric and HCC cohorts. Conclusions: Association between mutation status for TSC1/TSC2/mTOR and therapeutic outcome on everolimus was not confirmed. Clinically meaningful differences in PFS were seen based on PTEN expression by IHC, lost in >50% of patients.

The in vivo effects of melatonin on proliferation and apoptosis of 17-beta-estradiol (E2)-induced pituitary prolactin-secreting tumor (prolactinoma) were investigated in rats kept in 12 L/12 D (lights on: 06:00-18:00 hr). As melatonin was shown to induce apoptosis of breast and liver tumor cells, we examined whether melatonin would induce apoptosis of rat pituitary prolactinoma cells. 0.125, 0.25, 0.50 or 1.0 mg melatonin/day/rat was administrated subcutaneously at 17:30-18:00 hr. The weight of prolactinomas was measured. Apoptosis was evaluated using the TdT-mediated dUTP nick-end labeling method. It was found that treatment with 0.25 and 0.50 mg melatonin for 97 days inhibited prolactinoma cell proliferation and increased prolactinoma cell apoptosis. Furthermore, melatonin induced mRNA expression of Bax and cytochrome c protein expression. Conversely, mRNA expression of Bcl-2, and mitochondrial membrane potential were inhibited by melatonin treatment. These results suggest that melatonin inhibits the proliferation and induces apoptosis of rat pituitary prolactin-secreting tumor via perturbation of mitochondria physiology.

BACKGROUND: Our earlier studies indicate that melatonin inhibits the proliferation of prolactinoma and induces apoptosis of pituitary prolactin-secreting tumor in rats. Melatonin has also been shown to induce apoptosis and to reduce the production of ATP in breast tumor cells. This study analyzed the levels of the four mitochondrial respiratory complexes and the production of ATP and also the effects of melatonin treatment of prolactinoma. METHODS: In the in vivo study, mitochondria were harvested from control pituitaries or prolactinoma collected from the pituitaries of melatonin- and 17-β-estradiol (E2)-treated male rats. In the in vitro study, prolactinoma cells mitochondria were harvested. Activities of the four mitochondrial respiratory complexes were assayed using fluorometer. ATP production of prolactinoma cells was estimated using bioluminescent methods. RESULTS: Elevated levels of four mitochondrial respiratory complexes activities and ATP production were recorded in prolactinoma cells. Moreover, in both in vivo and in vitro studies, melatonin inhibited the activities of mitochondrial respiratory complexes and the production of ATP in prolactinoma cells. CONCLUSIONS: There is a link between mitochondrial function increase and tumorigenesis. Melatonin induces apoptosis of pituitary prolactin-secreting tumor of rats via the induction of mitochondrial dysfunction and inhibition of energy metabolism.

OBJECTIVE: To study the relationship between the polymorphism myeloperoxidase (MPO) gene and the genetic susceptibility to benzene toxicity in workers exposed to benzene and in patients with benzene poisoning. METHODS: Using polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) techniques, the genotypes' polymorphism of MPO gene in 35 patients with chronic benzene poisoning, 46 workers exposed to benzene from the same workplace (as exposed control) and 26 controls were analyzed. RESULT: There were three (G/G, G/A and A/A) genotypes in the region of 463 bp upstream of MPO gene. The distribution frequency in G/G wild-type genotype in patients was 27.4% more than that in the exposed workers. The risk of benzene-hematotoxicity in those with G/G genotype was 2.8-fold higher than G/A + A/A genotype (OR = 2.835, 95% CI: 1.065 - 7.549, P < 0.05). The polymorphism of myeloperoxidase was not associated with gender specific. CONCLUSION: In the same benzene-exposed environment, the subjects with MPO-463 G/G genotype may be more susceptible to benzene toxicity.