Comparison of laparoscopic and open inguinal-hernia repair in elderly patients: the experience of two comprehensive medical centers over 10 years.

PURPOSE: The safety of laparoscopic inguinal-hernia repair must be carefully evaluated in elderly patients. Very little is known regarding the safety of the laparoscopic approach in elderly patients under surgical and medical co-management (SMC). Therefore, this study evaluated the safety of the laparoscopic approach in elderly patients, especially patients with multiple comorbidities under SMC. METHODS: From January 2012 to December 2021, patients aged ≥ 65 years who underwent open or laparoscopic inguinal-hernia repair during hospitalization were consecutively enrolled. Postoperative outcomes included major and minor operation-related complications, and other adverse events. To reduce potential selection bias, propensity score matching was performed between open and laparoscopic groups based on patients' demographics and comorbidities. RESULTS: A total of 447 elderly patients who underwent inguinal-hernia repair were enrolled, with 408 (91.3%) underwent open and 39 (8.7%) laparoscopic surgery. All postoperative outcomes were comparable between open and laparoscopic groups after 1:1 propensity score matching (all p > 0.05). Moreover, compared to the traditional care group (n = 360), a higher proportion of the SMC group (n = 87) was treated via the laparoscopic approach (18.4% vs. 6.4%, p = 0.00). In the laparoscopic approach subgroup (n = 39), patients in the SMC group (n = 16) were older with multiple comorbidities but were at higher risks of only minor operation-related complications, compared to those in the traditional care group. CONCLUSIONS: Laparoscopic inguinal-hernia repair surgery is safe for elderly patients, especially those with multiple comorbidities under SMC.

Introduction to DOK2 and its potential role in cancer.

Cancer is a complex, multifactorial disease that modern medicine ultimately aims to overcome. Downstream of tyrosine kinase 2 (DOK2) is a well-known tumor suppressor gene, and a member of the downstream protein DOK family of tyrosine kinases. Through a search of original literature indexed in PubMed and other databases, the present review aims to extricate the mechanisms by which DOK2 acts on cancer, thereby identifying more reliable and effective therapeutic targets to promote enhanced methods of cancer prevention and treatment. The review focuses on the role of DOK2 in multiple tumor types in the lungs, intestines, liver, and breast. Additionally, we discuss the potential mechanisms of action of DOK2 and the downstream consequences via the Ras/MPAK/ERK or PI3K/AKT/mTOR signaling pathways.

[The clinical effects of oral contraceptive pretreatment on the outcome of gonadotropin releasing hormone antagonist protocol in non-polycystic ovary syndrome patients].

Objective: To evaluate the clinical effect of oral contraceptive (OC) pretreatment on the outcome of gonadotropin releasing hormone antagonist (GnRH-a) protocol in patients with non-polycystic ovary syndrome. Methods: From January 2017 to May 2019, a total of 436 patients undergoing in vitro fertilization and embryo transfer/Intracytoplasmic sperm injection (IVF-ET/ICSI) treatment in Peking University First Hospital reproductive center clinic were included in this retrospective cohort study. A total of 144 patients (147 cycles) used OC pretreatment prior to GnRH-a protocol and 292 patients (306 cycles) used GnRH-a protocol without OC pretreatment. The drug usage as well as pregnant outcomes between groups were examined. The primary outcome was the cumulative clinical pregnancy rate of oocyte retrieval cycle and the secondary outcome included the number of oocytes, MⅡ oocytes, embryos and clinical pregnancy rate of fresh embryo transfer cycle. Results: The median ages (and Q1, Q3) of OC pretreatment group and non-OC group were 33 (30,36) and 34 (30,38) years old, respectively. The number of MⅡ oocytes was higher in OC pretreatment group (7/9) than in non-OC group (6/8) (P=0.002). The significant difference were not found in the cumulative clinical pregnancy rate of each oocyte retrieval cycle (61.7% vs 54.6%), the clinical pregnancy rate of fresh embryo transfer cycle (34.4% vs 35.6%), and the number of oocytes (9 vs 8) and embryos (6 vs 6) between groups. Conclusion: Our findings suggest that compared to non-OC pretreatment group, pretreatment with OC is associated with more MⅡ oocytes, and with an increasing trend of the cumulative clinical pregnancy rate in non-polycystic ovary syndrome patients undergoing fresh IVF-ET/ICSI.

Proteogenomic insights into the biology and treatment of HPV-negative head and neck squamous cell carcinoma.

We present a proteogenomic study of 108 human papilloma virus (HPV)-negative head and neck squamous cell carcinomas (HNSCCs). Proteomic analysis systematically catalogs HNSCC-associated proteins and phosphosites, prioritizes copy number drivers, and highlights an oncogenic role for RNA processing genes. Proteomic investigation of mutual exclusivity between FAT1 truncating mutations and 11q13.3 amplifications reveals dysregulated actin dynamics as a common functional consequence. Phosphoproteomics characterizes two modes of EGFR activation, suggesting a new strategy to stratify HNSCCs based on EGFR ligand abundance for effective treatment with inhibitory EGFR monoclonal antibodies. Widespread deletion of immune modulatory genes accounts for low immune infiltration in immune-cold tumors, whereas concordant upregulation of multiple immune checkpoint proteins may underlie resistance to anti-programmed cell death protein 1 monotherapy in immune-hot tumors. Multi-omic analysis identifies three molecular subtypes with high potential for treatment with CDK inhibitors, anti-EGFR antibody therapy, and immunotherapy, respectively. Altogether, proteogenomics provides a systematic framework to inform HNSCC biology and treatment.

Noninvasive imaging evaluation of tumor immune microenvironment to predict outcomes in gastric cancer.

BACKGROUND: The tumor immune microenvironment can provide prognostic and predictive information. A previously validated ImmunoScore of Gastric Cancer (ISGC) evaluates both lymphoid and myeloid cells in the tumor core and invasive margin with immunohistochemical staining of surgical specimens. We aimed to develop a noninvasive radiomics-based predictor of ISGC. PATIENTS AND METHODS: In this retrospective study including four independent cohorts of 1778 patients, we extracted 584 quantitative features from the intratumoral and peritumoral regions on contrast-enhanced computed tomography images. A radiomic signature [radiomics ImmunoScore (RIS)] was constructed to predict ISGC using regularized logistic regression. We further evaluated its association with prognosis and chemotherapy response. RESULTS: A 13-feature radiomic signature for ISGC was developed and validated in three independent cohorts (area under the curve = 0.786, 0.745, and 0.766). The RIS signature was significantly associated with both disease-free and overall survival in the training and all validation cohorts [hazard ratio (HR) range: 0.296-0.487, all P < 0.001]. In multivariable analysis, the RIS remained an independent prognostic factor adjusting for clinicopathologic variables (adjusted HR range: 0.339-0.605, all P < 0.003). For stage II and stage III disease, patients with a high RIS derived survival benefit from adjuvant chemotherapy {HR = 0.436 [95% confidence interval (CI) 0.253-0.753], P = 0.002; HR = 0.591 (95% CI 0.428-0.818), P < 0.001, respectively}, whereas those with a low RIS did not. CONCLUSION: The RIS is a reliable tool for evaluation of immunoscore and retains the prognostic significance in gastric cancer. Future prospective studies are required to confirm its potential to predict treatment response and select patients who will benefit from chemotherapy.

Correlations of IL-6 and CRP gene polymorphisms with pulmonary heart disease.

OBJECTIVE: To explore the correlations of interleukin-6 (IL-6) and C-reactive protein (CRP) gene polymorphisms with pulmonary heart disease (PHD). PATIENTS AND METHODS: A total of 98 patients with PHD and 102 healthy persons receiving physical examinations were enrolled. Their general clinical information was collected, and the levels of IL-6 and CRP in the plasma were determined. The pulmonary functions and blood gas were detected, and the TaqMan-minor groove binder (MGB) probe was used to detect the polymorphisms of IL-6 rs1800796 and CRP rs1800796. RESULTS: Observation group had higher levels of IL-6 and CRP than control group (p<0.05). The forced expiratory volume in 1 second (FEV1) (%), FEV1/forced vital capacity (FVC) ratio (%), and arterial partial pressure of oxygen (PaO2) in observation group were lower than those in control group (p<0.05), but the arterial partial pressure of carbon dioxide (PaCO2) was higher than that in control group (p<0.05). There were differences in the distribution frequencies of the genotypes and alleles of IL-6 rs1800796 and CRP rs1800796 between the two groups (p<0.05). CONCLUSIONS: IL-6 and CRP are correlated with the onset of PHD, and there are also correlations between the polymorphisms of IL-6 rs1800796 and CRP rs2794521 and the disease.

HDAC7 regulates histone 3 lysine 27 acetylation and transcriptional activity at super-enhancer-associated genes in breast cancer stem cells.

Chromatin regulation through histone modifications plays an essential role in coordinated expression of multiple genes. Alterations in chromatin induced by histone modifiers and readers regulate critical transcriptional programs involved in both normal development and tumor differentiation. Recently, we identified that histone deacetylases HDAC1 and HDAC7 are necessary to maintain cancer stem cells (CSCs) in both breast and ovarian tumors. Here, we sought to investigate the CSC-specific function of HDAC1 and HDAC7 mechanistically by using a stem-like breast cancer (BrCa) cell model BPLER and matched nonstem tumor cell (nsTC)-like HMLER, along with conventional BrCa cell lines with different CSC enrichment levels. We found that HDAC1 and HDAC3 inhibition or knockdown results in HDAC7 downregulation, which is associated with a decrease in histone 3 lysine 27 acetylation (H3K27ac) at transcription start sites (TSS) and super-enhancers (SEs) prominently in stem-like BrCa cells. Importantly, these changes in chromatin landscape also correlate with the repression of many SE-associated oncogenes, including c-MYC, CD44, CDKN1B, SLUG, VDR, SMAD3, VEGFA, and XBP1. In stem-like BrCa cells, HDAC7 binds near TSS and to SEs of these oncogenes where it appears to contribute to both H3K27ac and transcriptional regulation. These results suggest that HDAC7 inactivation, directly or through inhibition of HDAC1 and HDAC3, can result in the inhibition of the CSC phenotype by downregulating multiple SE-associated oncogenes. The CSC selective nature of this mechanism and the prospect of inhibiting multiple oncogenes simultaneously makes development of HDAC7 specific inhibitors a compelling objective.

Effect of health education combining diet and exercise supervision in Chinese women with perimenopausal symptoms: a randomized controlled trial.

OBJECTIVE: This study aimed to evaluate the effect of health education combining diet and exercise supervision on menopausal symptoms and diet/exercise habits. METHODS: The randomized controlled study enrolled 60 patients with perimenopausal syndrome (Kupperman Menopause Index (KMI) score ≥15). The participants were randomized into either an intervention group (n = 30) or a control group (n = 30). Women were interviewed with questionnaires about perimenopausal symptoms, diet pattern and exercise habit. Their height and weight were measured. Women in the intervention group received health education, diet supervision and exercise supervision twice a week while those in the control group continued as normal. The total KMI score, scores of individual symptoms, diet pattern and exercise habit were measured after intervention. RESULTS: The total KMI score, the individual KMI scores for paresthesia, irritability, depression/suspicious, fatigue, arthralgia/myalgia, and palpitations of the intervention group were significantly lower compared with the control group after intervention. The intake of cereal, meat, fats and oils of the intervention group were significantly lower at week 12 compared with baseline. The percentage of women with a regular exercise habit was significantly higher in the intervention group than in the control group after intervention. CONCLUSIONS: Twelve weeks intervention of health education combining diet and exercise supervision could improve perimenopausal symptoms and help the patients establish good living habits.

Construction of the mammalian expressing vector pEGFP-N1-P53 and its expression successful in chicken fibroblast cells and blastoderm.

The enhanced green fluorescent protein (EGFP) pEGFP-N1-P53 eukaryotic expression vector, which contains the human tumor suppressor p53, was constructed and transfected into chicken fibroblast cells and stage-X blastoderm to analyze the transfection efficiency. The complementary DNA of the human p53 gene was cloned by reverse transcription-polymerase chain reaction from human peripheral blood and inserted into the pEGFP-N1 vector by HindIII and BamHI double digestion. The pEGFP-N1-P53 vector was transfected into chicken embryo fibroblasts by Lipofectamine 2000 liposomes, and the transfection efficiency was analyzed by fluorescence microscope after 36 h of transfection. The stage-X blastoderm was also transfected by blastoderm injection using Lipofectamine 2000 liposomes at room temperature after 12-24 h; then hatching occurred until seventh day, and the transfection efficiency was analyzed by fluorescence microscope in the dead embryo. A total of 90 hatching eggs were transfected by the pEGFP-N1-P53 vector, and 20 chicken embryos expressed the reporter gene, which indicated that recombinant pEGFP-N1-P53 could be transfected and expressed in stage-X blastoderm by liposomes. Chicken embryo fibroblasts were transfected and expressed the reporter gene. The pEGFP-N1-P53 vector was constructed successfully and could be transfected and expressed in chicken embryo fibroblasts and stage-X blastoderms efficiently.

Cigarette smoke mediates epigenetic repression of miR-217 during esophageal adenocarcinogenesis.

Although microRNAs (miRs) have been implicated in the pathogenesis of various human malignancies, limited information is available regarding mechanisms by which these noncoding RNAs contribute to initiation and progression of tobacco-induced esophageal cancers. In this study, array and quantitative reverse transcriptase-PCR techniques were used to examine miR expression in immortalized esophageal epithelia (IEE) and esophageal adenocarcinoma (EAC) cells cultured in normal media with or without cigarette smoke condensate (CSC). Under relevant exposure conditions, CSC significantly decreased miR-217 expression in these cells. Endogenous levels of miR-217 expression in cultured EAC cells (EACC)/primary EACs were significantly lower than those observed in IEE/ paired normal esophageal tissues. RNA crosslink immunoprecipitation, quantitative reverse transcriptase-PCR (qRT-PCR) and immunoblot experiments demonstrated direct interaction of miR-217 with kallikrein 7 (KLK7), encoding a putative oncogene not previously implicated in EAC. Repression of miR-217 correlated with increased levels of KLK7 in primary EACs, particularly those from smokers. Chromatin and methylated DNA immunoprecipitation experiments demonstrated that CSC-mediated repression of miR-217 coincided with DNMT3b-dependent hypermethylation and decreased occupancy of nuclear factor 1 within the miR-217 genomic locus. Deoxyazacytidine induced miR-217 expression and downregulated KLK7 in EACC; deoxyazacytidine also attenuated CSC-mediated miR-217 repression and upregulation of KLK7 in IEE and EACC. Overexpression of miR-217 significantly decreased, whereas overexpression of KLK7 increased proliferation, invasion and tumorigenicity of EACC. Collectively, these data demonstrate that epigenetic repression of miR-217 contributes to the pathogenesis of EAC via upregulation of KLK7 and suggest that restoration of miR-217 expression may be a novel treatment strategy for these malignancies.

Epigenomic alterations and gene expression profiles in respiratory epithelia exposed to cigarette smoke condensate.

Limited information is available regarding epigenomic events mediating initiation and progression of tobacco-induced lung cancers. In this study, we established an in vitro system to examine epigenomic effects of cigarette smoke in respiratory epithelia. Normal human small airway epithelial cells and cdk-4/hTERT-immortalized human bronchial epithelial cells (HBEC) were cultured in normal media with or without cigarette smoke condensate (CSC) for up to 9 months under potentially relevant exposure conditions. Western blot analysis showed that CSC mediated dose- and time-dependent diminution of H4K16Ac and H4K20Me3, while increasing relative levels of H3K27Me3; these histone alterations coincided with decreased DNA methyltransferase 1 (DNMT1) and increased DNMT3b expression. Pyrosequencing and quantitative RT-PCR experiments revealed time-dependent hypomethylation of D4Z4, NBL2, and LINE-1 repetitive DNA sequences; up-regulation of H19, IGF2, MAGE-A1, and MAGE-A3; activation of Wnt signaling; and hypermethylation of tumor suppressor genes such as RASSF1A and RAR-beta, which are frequently silenced in human lung cancers. Array-based DNA methylation profiling identified additional novel DNA methylation targets in soft-agar clones derived from CSC-exposed HBEC; a CSC gene expression signature was also identified in these cells. Progressive genomic hypomethylation and locoregional DNA hypermethylation induced by CSC coincided with a dramatic increase in soft-agar clonogenicity. Collectively, these data indicate that cigarette smoke induces 'cancer-associated' epigenomic alterations in cultured respiratory epithelia. This in vitro model may prove useful for delineating early epigenetic mechanisms regulating gene expression during pulmonary carcinogenesis.

Gene therapy for the treatment of oral squamous cell carcinoma.

Despite advances in surgery, radiotherapy, and chemotherapy, the survival of patients with oral squamous cell carcinoma has not significantly improved over the past several decades. Treatment options for recurrent or refractory oral cancers are limited. Gene therapy for oral cancer is currently under investigation in clinical trials. The goal of cancer gene therapy is to introduce new genetic material into target cells without toxicity to non-target tissues. This review discusses the techniques used in cancer gene therapy for oral squamous cell carcinoma and summarizes the ongoing strategies that are being evaluated in clinical trials.

Inhibition of androgen-sensitive LNCaP prostate cancer growth in vivo by melatonin: association of antiproliferative action of the pineal hormone with mt1 receptor protein expression.

BACKGROUND: Potential involvement of the mt1 receptor in the antiproliferative action of melatonin on androgen-sensitive LNCaP cells, and melatonin-induced modulation of androgen-insensitive PC-3 cell growth, have been reported in vitro. The effects of melatonin on prostate cancer cell proliferation and their association with mt1 receptor expression were investigated in athymic nude mice xenograft models of LNCaP and PC-3 cells. METHODS: Daily saline or melatonin (4 microg/g body weight) was given to nude mice before or after tumor cell inoculation. Tumor volume was measured periodically, and expression of PCNA, cyclin A, PSA, and mt1 receptor was assessed by immunohisto(cyto)chemistry and/or Western blotting. RESULTS: Melatonin inhibited the growth of LNCaP tumors, without affecting the growth of PC-3 xenografts, in nude mice. It induced significant decreases in the expression of PCNA, cyclin A, and PSA in LNCaP tumors. Expression of mt1 receptor protein was demonstrated in LNCaP cells, but not in PC-3 cells, both in vivo and in vitro. CONCLUSIONS: The antiproliferative action of melatonin on LNCaP tumor growth was demonstrated in vivo, and its association with mt1 receptor protein expression suggests the potential involvement of the receptor in the antitumor activity of the pineal gland hormone.

[The cytotoxic effect of a low density lipoprotein delivered aclarubicin on leukemia cells].

OBJECTIVE: To investigate the feasibility and effectiveness of low density lipoprotein (LDL) particles as a carrier of a lipophilic anthracycline drug aclarubicin (ACR) for targeting delivery to an acute monocytic leukemia cell line THP-1. METHODS: LDL-ACR complex was prepared by incubating LDL with ACR. The intracellular ACR content was assayed fluorometrically. Cytotoxicity was studied by cell protein measurement and 3H-TdR incorporation test. RESULTS: Intracellular accumulation of LDL-ACR was reduced when THP-1 cells were incubated in the presence of native LDL, but methylated LDL had no effect on the cellular LDL-ACR accumulation. The LDL-ACR complex caused a greater inhibition of the growth of THP-1 cells than that of normal bone marrow nucleated cells. The cellular accumulation of LDL-ACR complex was much more than that of free ACR. The 3H-TdR incorporation test showed that the complex was more effective in the inhibition of DNA synthesis than that of the free drug. CONCLUSION: The potency of ACR to tumor cells increased and its toxicity to normal cells decreased when LDL was used as a carrier.

Inhibition of malignant trophoblastic cell proliferation in vitro and in vivo by melatonin.

Melatonin inhibited thymidine incorporation into human choriocarcinoma JEG-3 cells at physiological and pharmacological concentrations in the present study. Gene expression of MT2 receptor, but not that of mt1 receptor, was detected in JEG-3 cells by reverse transcription-polymerase chain reaction (RT-PCR). The gene expression profile of the two human melatonin receptor subtypes in JEG-3 cells was identical to that previously reported for JAr cells, whose proliferation had also been shown to be similarly inhibited by physiological and pharmacological concentrations of melatonin. In contrast, melatonin had no effect on thymidine incorporation into 3A-Sub-E cells (a transformed trophoblast cell line), in which gene expression of both receptor subtypes could not be detected. The data suggest that in human placental trophoblasts, a correlation may exist between MT2 receptor gene expression and the direct anti-proliferative action of melatonin. Although melatonin has been reported to induce G1/S delay in cell cycle progression of JAr cells, no significant changes in the percentages of JEG-3 cells in different cell cycle phases upon melatonin treatment was recorded by flow cytometric analysis. This indicates that G1/S transition delay is probably not an important cellular mechanism in the direct anti-proliferative action of melatonin on human JEG-3 cells in vitro. Furthermore, melatonin inhibited the growth of both JAr and JEG-3 xenograft tumors in athymic nude mice, and prolonged the survival of those animals that developed choriocarcinoma. While the number of apoptotic tumor cells was not increased by melatonin, the pineal hormone induced significant decreases in the numbers of JAr and JEG-3 cells expressing proliferating cell nuclear antigen (PCNA) and cyclin A in the tumors. Taking into account both the in vitro and in vivo findings, it is likely that the inhibitory effect of melatonin on choriocarcinoma JAr and JEG-3 cell proliferation in vivo is largely a direct action of the hormone on the tumor cells.

Potential involvement of mt1 receptor and attenuated sex steroid-induced calcium influx in the direct anti-proliferative action of melatonin on androgen-responsive LNCaP human prostate cancer cells.

Melatonin, a pineal secretory product, has been shown to exert a direct anti-proliferative action on the androgen-sensitive LNCaP prostate cancer cell line through hitherto undefined mechanisms. In this communication, expression of mt1 melatonin receptor protein in human prostate cancer tissues and LNCaP cells was demonstrated by immunohisto(cyto)chemistry and western blotting, hence supporting the use of LNCaP cell line as a model for the study of melatonin signaling in prostate cancer cell growth. Using 3H-thymidine incorporation assay, LNCaP cell proliferation was inhibited by 2-iodomelatonin, a high-affinity melatonin receptor agonist. Furthermore, melatonin inhibited 3H-thymidine incorporation into LNCaP cells and attenuated 5alpha-dihydrotestosterone (DHT) or 17beta-estradiol (E2)-induced stimulation of LNCaP cell proliferation at physiological and pharmacological concentrations. Similar concentration-dependent inhibition of sex steroid-induced stimulation of thymidine incorporation into LNCaP cells by 2-iodomelatonin was also observed. Interestingly, attenuation of sex steroid-stimulated calcium influx into LNCaP cells by pharmacological concentrations of melatonin was recorded, whereas 2-iodomelatonin had no effect on cytosolic calcium changes induced by sex steroids. In addition, proliferative and cytosolic calcium changes were associated with inhibition of total prostate-specific antigen (PSA) production by LNCaP cells at high physiological and pharmacological concentrations of melatonin. Our data suggest that activated mt1 receptor and attenuated sex steroid-induced calcium influx are two important mechanisms mediating the direct anti-proliferative action of melatonin on androgen-responsive human prostate cancer cells.

15-hydroxyeicosatrienoic acid (15-HETrE) suppresses epidermal hyperproliferation via the modulation of nuclear transcription factor (AP-1) and apoptosis.

The purpose of this study was to ascertain whether the antiproliferative effect of 15-hydroxyeicosatrienoic acid (15-HETrE), a monohydroxy fatty acid generated from dihomo-gamma-linolenic acid, in an experimentally induced guinea pig hyperproliferative model involves alterations in nuclear transcription factor (AP-1) and apoptosis. The topical application of docosahexaenoic acid (DHA) to normal guinea pig skin elicited a severe hyperplasia which was accompanied by the suppression of AP-1 expression in a time-dependent manner. Since apoptosis is pivotal in tissue turnover, the expression of two apoptotic proteins (Bcl-2 and caspase-3) after DHA and 15-HETrE treatment was explored. DHA-induced hyperproliferation enhanced the expression of Bcl-2 (an antiapoptotic protein) but inhibited the expression of caspase-3 (an apoptotic protein). 15-HETrE, on the other hand, reversed the DHA-induced epidermal hyperplasia, and upregulated epidermal AP-1 expression. These events paralleled the suppression of Bcl-2 and the elevation of caspase-3. Taken together, these results suggest that the antiproliferative effect of 15-HETrE may, at least in part, be via the modulation of AP-1 and apoptosis.

Biological basis and possible physiological implications of melatonin receptor-mediated signaling in the rat epididymis.

The mammalian epididymis plays an important role in sperm maturation, an important process of male reproduction. Specific high-affinity 2-[(125)I]iodomelatonin binding sites, satisfying the pharmacokinetic properties of specific receptors, have been found in the rat corpus epididymis, suggesting a direct melatonin action on epididymal physiology. Subsequent molecular and cell biology studies have identified these 2-[(125)I]iodomelatonin binding sites to be mt(1) (MEL(1A)) and MT(2) (MEL(1B)) melatonin receptor subtypes. Changes in the binding characteristics of these receptors in the rat corpus epididymis in response to castration and steroid hormones like testosterone and hydrocortisone indicated that these membrane melatonin receptors are biologically functional receptors, whose activities are differentially regulated by testosterone and hydrocortisone. These melatonin receptors are coupled to pertussis toxin (PTX)-sensitive G(i) protein and probably participate in androgenic and adrenergic regulation of rat corpus epididymal epithelial cell functions. Furthermore, rat corpus epididymal epithelial cell proliferation was stimulated by melatonin, whose action was dependent on the concentration and duration of exposure to the hormone. Interestingly, an MT(2) receptor ligand (4-phenyl-2-propionamidotetraline, 4-P-PDOT) induced a stimulatory effect on epididymal epithelial cell proliferation similar to that produced by melatonin. In contrast, a nuclear melatonin receptor agonist (1-[3-allyl-4-oxo-thiazolidine-2-ylidene]-4-methyl-thiosemi-car bazone , CGP52608) and 8-bromo-cAMP inhibited epididymal epithelial cell proliferation. Taken together, our data lead us to postulate that one of the possible physiological functions of melatonin on the rat epididymis is the stimulation of mt(1) and MT(2) melatonin receptors resulting in the inhibition of cAMP signaling and an increase in epithelial cell proliferation.