Mullerian inhibiting substance promotes interferon gamma-induced gene expression and apoptosis in breast cancer cells

Possible role of endoplasmic reticulum stress in the pathogenesis of chronic adenoiditis and adenoid hypertrophy: A prospective, parallel-group study

Background

Adenoid tissue is a first-line host defense secondary lymphoid organ, especially in childhood. The endoplasmic reticulum (ER) is required to maintain balanced cellular activity. With impaired ER functions, protein accumulation occurs, resulting in ER stress, which plays a role in the etiopathogenesis of many diseases.

Objective

We aimed to investigate the relationship between ER stress and adenoid tissue disorders, thereby elucidating the mechanisms of immunity-related diseases.

Methods

Fifty-four pediatric patients (>3 years old) who underwent adenoidectomy for chronic adenoiditis (CA) or adenoid hypertrophy (AH) were enrolled in this prospective, parallel-group clinical study. Adenoids were divided into two groups (CA or AH) based on their size and evaluated for ER stress pathway and apoptosis pathway markers by Real-time PCR and Western blot analysis.

Results

ER stress pathway markers significantly differed between the CA and AH groups. Children with CA had higher ER stress marker levels than the AH group (p < .001 for ATF-4, ATF-6, and GRP78, and p < .05 for EDEM1, CHOP, EIF2AK3, ERNI, and GRP94). Apoptosis pathway marker levels (BAX and BCL-2) were not different between groups.

Conclusions

ER stress contributes to the etiopathogenesis of adenoid tissue diseases and the pathogenesis of adenoid tissue disorders, which are part of the immune response. These results may guide the development of new and alternative treatments for immune system disorders.

Anti-Müllerian hormone levels and breast cancer risk in the study of women's health across the nation

PURPOSE

The relation of premenopausal anti-Müllerian hormone (AMH) levels with breast cancer risk has been evaluated in a few studies, but primarily in non-Hispanic White women.

METHODS

We evaluated the association of AMH levels with breast cancer risk in Study of Women's Health Across the Nation (SWAN), a multi-ethnic cohort of women. At enrollment, participants had an intact uterus and ≥ 1 ovary, and ≥ 1 menstrual period in the last 3 months. AMH at first measurement was assessed in 1,529 pre- or perimenopausal women using a high-sensitivity ELISA assay; values were natural log transformed. Breast cancer diagnoses were assessed at enrollment and subsequent follow-up visits through 2018 (median 6.1 years).

RESULTS

In total, 84 women reported an incident breast cancer diagnosis. In multivariable Cox regression models adjusting for age, race and ethnicity, body mass index, and other factors, higher AMH levels were associated with a non-significant increased breast cancer risk. Compared to women in the 1st quartile, the hazard ratio (95% confidence interval) for women in the 4th quartile was 1.77 (0.87-3.60).

CONCLUSION

Our results did not suggest a significant association between AMH and breast cancer risk; however, estimates were consistent with prior studies that reported positive associations.

Anti-Müllerian Hormone in Female Reproduction

Anti-Müllerian hormone (AMH), also called Müllerian inhibiting substance, was shown to be synthesized by the ovary in the 1980s. This article reviews the main findings of the past 20 years on the regulation of the expression of AMH and its specific receptor AMHR2 by granulosa cells, the mechanism of action of AMH, the different roles it plays in the reproductive organs, its clinical utility, and its involvement in the principal pathological conditions affecting women. The findings in respect of regulation tell us that AMH and AMHR2 expression is mainly regulated by bone morphogenetic proteins, gonadotropins, and estrogens. It has now been established that AMH regulates the different steps of folliculogenesis and that it has neuroendocrine effects. On the other hand, the importance of serum AMH as a reliable marker of ovarian reserve and as a useful tool in the prediction of the polycystic ovary syndrome (PCOS) and primary ovarian failure has also been acknowledged. Last but not least, a large body of evidence points to the involvement of AMH in the pathogenesis of PCOS.

Circulating anti-Müllerian hormone and breast cancer risk: A study in ten prospective cohorts

A strong positive association has been observed between circulating anti-Müllerian hormone (AMH), a biomarker of ovarian reserve, and breast cancer risk in three prospective studies. Confirming this association is important because of the paucity of biomarkers of breast cancer risk in premenopausal women. We conducted a consortium study including ten prospective cohorts that had collected blood from premenopausal women. A nested case-control design was implemented within each cohort. A total of 2,835 invasive (80%) and in situ (20%) breast cancer cases were individually matched to controls (n = 3,122) on age at blood donation. AMH was measured using a high sensitivity enzyme-linked immunoabsorbent assay. Conditional logistic regression was applied to the aggregated dataset. There was a statistically significant trend of increasing breast cancer risk with increasing AMH concentration (ptrend across quartiles <0.0001) after adjusting for breast cancer risk factors. The odds ratio (OR) for breast cancer in the top vs. bottom quartile of AMH was 1.60 (95% CI = 1.31-1.94). Though the test for interaction was not statistically significant (pinteraction  = 0.15), the trend was statistically significant only for tumors positive for both estrogen receptor (ER) and progesterone receptor (PR): ER+/PR+: ORQ4-Q1  = 1.96, 95% CI = 1.46-2.64, ptrend <0.0001; ER+/PR-: ORQ4-Q1  = 0.82, 95% CI = 0.40-1.68, ptrend  = 0.51; ER-/PR+: ORQ4-Q1  = 3.23, 95% CI = 0.48-21.9, ptrend  = 0.26; ER-/PR-: ORQ4-Q1  = 1.15, 95% CI = 0.63-2.09, ptrend  = 0.60. The association was observed for both pre- (ORQ4-Q1 = 1.35, 95% CI = 1.05-1.73) and post-menopausal (ORQ4-Q1  = 1.61, 95% CI = 1.03-2.53) breast cancer (pinteraction  = 0.34). In this large consortium study, we confirmed that AMH is associated with breast cancer risk, with a 60% increase in risk for women in the top vs. bottom quartile of AMH.

IRF-1 inhibits NF-κB activity, suppresses TRAF2 and cIAP1 and induces breast cancer cell specific growth inhibition

Interferon Regulatory Factor (IRF)-1, originally identified as a transcription factor of the human interferon (IFN)-β gene, mediates tumor suppression and may inhibit oncogenesis. We have shown that IRF-1 in human breast cancer cells results in the down-regulation of survivin, tumor cell death, and the inhibition of tumor growth in vivo in xenogeneic mouse models. In this current report, we initiate studies comparing the effect of IRF-1 in human nonmalignant breast cell and breast cancer cell lines. While IRF-1 in breast cancer cells results in growth inhibition and cell death, profound growth inhibition and cell death are not observed in nonmalignant human breast cells. We show that TNF-α or IFN-γ induces IRF-1 in breast cancer cells and results in enhanced cell death. Abrogation of IRF-1 diminishes TNF-α and IFN-γ-induced apoptosis. We test the hypothesis that IRF-1 augments TNF-α-induced apoptosis in breast cancer cells. Potential signaling networks elicited by IRF-1 are investigated by evaluating the NF-κB pathway. TNF-α and/or IFN-γ results in decreased presence of NF-κB p65 in the nucleus of breast cancer cells. While TNF-α and/or IFN-γ can induce IRF-1 in nonmalignant breast cells, a marked change in NF-κB p65 is not observed. Moreover, the ectopic expression of IRF-1 in breast cancer cells results in caspase-3, -7, -8 cleavage, inhibits NF-κB activity, and suppresses the expression of molecules involved in the NF-κB pathway. These data show that IRF-1 in human breast cancer cells elicits multiple signaling networks including intrinsic and extrinsic cell death and down-regulates molecules involved in the NF-κB pathway.

Plasma Anti-Müllerian Hormone Concentrations and Risk of Breast Cancer among Premenopausal Women in the Nurses' Health Studies

BACKGROUND

Anti-Müllerian hormone (AMH) is a member of the TGFβ family of growth and differentiation factors with a key role in regulating folliculogenesis. In experimental studies, using supraphysiologic concentrations, AMH inhibits breast cancer growth. However, high levels of AMH were associated with increased breast cancer risk in two prior prospective epidemiologic studies.

METHODS

We conducted a nested case-control study of premenopausal plasma AMH and breast cancer risk within the Nurses' Health Study (NHS) and NHSII. In NHS, 32,826 women donated blood samples in 1989-1990; in NHSII, 29,611 women donated samples in 1996-1999. After blood collection and before February 2004 (NHS) or July 2010 (NHSII), 539 cases were diagnosed among women premenopausal at diagnosis, and were matched 1:1 to controls. ORs and 95% confidence intervals (CI) were calculated using unconditional logistic regression, adjusting for matching and breast cancer risk factors.

RESULTS

Higher plasma levels of AMH were associated with increased breast cancer risk (top vs. bottom quintile multivariate OR, 2.20; 95% CI, 1.34-3.63; P trend = 0.001). The association did not vary by invasive versus in situ disease or by estrogen receptor status. Associations were not significantly different by age at blood or diagnosis. Further adjustment for plasma estradiol or testosterone yielded similar results.

CONCLUSIONS

Higher circulating AMH levels are associated with increased breast cancer risk among premenopausal women.

IMPACT

The significant positive association between premenopausal plasma AMH levels and subsequent breast cancer risk before menopause suggests AMH may be useful as a marker of breast cancer risk in younger women. Cancer Epidemiol Biomarkers Prev; 25(5); 854-60. ©2016 AACR.

Müllerian inhibiting substance/anti-Müllerian hormone: A novel treatment for gynecologic tumors

Müllerian inhibiting substance (MIS), also called anti-Müllerian hormone (AMH), is a member of the transforming growth factor-β super-family of growth and differentiation response modifiers. It is produced in immature Sertoli cells in male embryos and binds to MIS/AMH receptors in primordial Müllerian ducts to cause regression of female reproductive structures that are the precursors to the fallopian tubes, the surface epithelium of the ovaries, the uterus, the cervix, and the upper third of the vagina. Because most gynecologic tumors originate from Müllerian duct-derived tissues, and since MIS/AMH causes regression of the Müllerian duct in male embryos, it is expected to inhibit the growth of gynecologic tumors. Purified recombinant human MIS/AMH causes growth inhibition of epithelial ovarian cancer cells and cell lines in vitro and in vitro via MIS receptor-mediated mechanism. Furthermore, several lines of evidence suggest that MIS/AMH inhibits proliferation in tissues and cell lines of other MIS/AMH receptor-expressing gynecologic tumors such as cervical, endometrial, breast, and in endometriosis as well. These findings indicate that bioactive MIS/AMH recombinant protein should be tested in patients against tumors expressing the MIS/AMH receptor complex, perhaps beginning with ovarian cancer because it has the worst prognosis. The molecular tools to identify MIS/AMH receptor expressing ovarian and other cancers are in place, thus, it is possible to select patients for treatment. An MIS/AMH ELISA exists to follow administered doses of MIS/AMH, as well. Clinical trials await the production of sufficient supplies of qualified recombinant human MIS/AMH for this purpose.

The inhibin-βC subunit is down-regulated, while inhibin-βE is up-regulated by interferon-β1a in Ishikawa carcinoma cell line

INTRODUCTION

Inhibins are important regulators of the female reproductive system. Recently, two new inhibin-subunits βC and βE have been described, although, their function is still quite unclear. Interestingly, there is an association between interferon and TGF-β expression. Therefore, the aim of this study was to determine expression changes of inhibin-βC and -βE subunits in endometrial Ishikawa carcinoma cell line after stimulation with interferon-β1a.

MATERIALS AND METHODS

The Ishikawa cell line was cultured until confluence was observed (after 2 days). After adding interferon-β1a (1,000 IE/ml), Ishikawa cells were analyzed for inhibin-βC and -βE subunits by RT-PCR. The fibroblast cell line BJ6 served as negative control. Experiments were performed in triplicates.

RESULTS

The endometrial adenocarcinoma cell line Ishikawa synthesized the inhibin- βC and -βE subunits. The fibroblast cells BJ6 did not demonstrate an inhibin -βC and -βE mRNA expression, while inhibin-βC subunit is down-regulated and inhibin-βE is up-regulated in Ishikawa carcinoma cell line after stimulation with interferon-β1a in Ishikawa.

DISCUSSION

We demonstrated for the first time a functional relationship between interferon and the novel inhibin-βC and -βE subunits. It might be possible that interferon exerts a possible apoptotic function through the βE-subunit, while, by down-regulating the βC isoform, cell proliferation is inhibited. However, the precise function of the novel βC- and βE-subunits are still not known in human endometrial tissue and a possible association with interferon is still unclear and warrants further research.

The Role of Interferon Regulatory Factor-1 (IRF1) in Overcoming Antiestrogen Resistance in the Treatment of Breast Cancer

Resistance to endocrine therapy is common among breast cancer patients with estrogen receptor alpha-positive (ER+) tumors and limits the success of this therapeutic strategy. While the mechanisms that regulate endocrine responsiveness and cell fate are not fully understood, interferon regulatory factor-1 (IRF1) is strongly implicated as a key regulatory node in the underlying signaling network. IRF1 is a tumor suppressor that mediates cell fate by facilitating apoptosis and can do so with or without functional p53. Expression of IRF1 is downregulated in endocrine-resistant breast cancer cells, protecting these cells from IRF1-induced inhibition of proliferation and/or induction of cell death. Nonetheless, when IRF1 expression is induced following IFNγ treatment, antiestrogen sensitivity is restored by a process that includes the inhibition of prosurvival BCL2 family members and caspase activation. These data suggest that a combination of endocrine therapy and compounds that effectively induce IRF1 expression may be useful for the treatment of many ER+ breast cancers. By understanding IRF1 signaling in the context of endocrine responsiveness, we may be able to develop novel therapeutic strategies and better predict how patients will respond to endocrine therapy.

Müllerian inhibiting substance/anti-Müllerian hormone: a potential therapeutic agent for human ovarian and other cancers

According to the 2008 American Cancer Society statistics, cancer remains the second leading cause of death in American today. Early detection, innovative surgery, new drugs and increased public education regarding avoidable risk factors, such as smoking, have had significant impact on the incidence and survival rates of many cancers, while overall death rates from all cancers have declined a modest 5% over the past 50 years. Ovarian cancer statistics, however, have not been as encouraging. Despite recent advances in the management of this disease, 5-year survival has not improved, and the search continues for rationally designed new treatments. Müllerian Inhibiting Substance is a strong candidate because it addresses many of the deficiencies of existing treatments. Namely, Müllerian Inhibiting Substance has little demonstrated toxicity, it complements the activity of known anticancer drugs, it is highly specific against cancers expressing its receptor and it inhibits the proliferation of drug-resistant tumors.

Development of an efficiently cleaved, bioactive, highly pure FLAG-tagged recombinant human Mullerian Inhibiting Substance

Mullerian Inhibiting Substance (MIS), a member of the TGF-beta family, causes regression of the Mullerian duct in male embryos, after binding to Mullerian Inhibiting Substance Receptor II (MISRII). It has also been extensively demonstrated that it can inhibit proliferation of various cancer cell lines such as ovarian, prostate, and breast cancer in vitro and in vivo. Hence, the availability of a recombinant, epitope tagged, bioactive MIS is important for the selection of patients for treatment and for probing novel molecular targets for MIS in various tissues. To this end, we have expressed a recombinant, internally FLAG-tagged form of hMIS with the tag (DYKDDDDK) immediately after the cleavage site (427-428) of MIS at the C-terminus with a modified dibasic cleavage motif sequence. We show that this construct results in a highly pure, endogenously processed (cleaved) FLAG MIS, that causes complete regression of the Mullerian Duct in an organ culture assay. In addition, purified FLAG MIS was able to bind and affinity purify both transfected and endogenous MIS type II receptor. The availability of this fully functional, epitope tagged form of MIS should facilitate scale-up for preclinical and clinical use and should also be used for the study of MIS binding proteins and for tracking in pharmacokinetic studies.

Interferon-gamma bolsters CD95/Fas-mediated apoptosis of astroglioma cells

In the present study, we investigated the mechanisms of the resistance to CD95-mediated cell death and the effects of interferon-gamma in modulating the susceptibility to CD95-induced apoptosis of human astroglioma cells. We found that interferon-gamma administration sensitized cancer cells to CD95-mediated apoptosis. The mechanism underlying this sensitization appeared to be associated with a framework of cell changes, including up-regulation of death receptor at the cell surface, pro-apoptotic molecule Bax and Bak over-expression and mitochondria hyperpolarization, as is known to be associated with cell sensitization to apoptosis. An involvement of the proteasome activity in the mechanism of sensitization by interferon-gamma was also detected, probably as a result of the differing expression of catalytic proteasome subunits. Taken together, these findings suggest that interferon-gamma could represent a promising candidate for modulating astroglioma cell apoptotic susceptibility.

IRF-1 promotes apoptosis in p53-damaged basal-type human mammary epithelial cells: a model for early basal-type mammary carcinogenesis

Mammary gland homeostasis is regulated by both endogenous and exogenous signals, creating a balance between proliferation and apoptosis. It is thought that breast cancer develops from the acquisition of multiple genetic changes. The function of tumor suppressor p53 is fequently lost in cancers; however, not all cells that lose p53 progress to become invasive cancer. We have developed a model of early mammary carcinogenesis to investigate some of the internal and external signaling pathways that target the elimination ot normal basal-type human mammary epithelial cells (HMECs) that acutely acquire p53-damage. Here, we show that both tamoxifen (Tam) and three-dimensional prepared extracellular matrix culture (3-D rECM) induce apoptosis in HMEC cells with acute loss of p53 [*p53(-) HMECs] through induction of interferon regulatory factor-1 (IRF-1). Tam and rECM signaling in *p53(-) HMECs (1) promotes the recruitment of a STAT1/ CBP complex to the IRF-1 promoter, (2) upregulates IRF-1, (3) activates caspase-1 and -3, and (4) induces apoptosis. Suppression of IRF-1 with siRNA oligos inhibited both Tam- and rECM-induced apoptosis. These observations demonstrate that IRF-1 plays a critical role in eliminating p53-damaged cells, and may play a more global role in mammary gland homeostasis.

Müllerian inhibiting substance type II receptor (MISIIR): a novel, tissue-specific target expressed by gynecologic cancers

OBJECTIVE

Müllerian inhibiting substance type II receptor (MISIIR) is expressed by ovarian, breast, and prostate cancers [Masiakos PT, et al. Human ovarian cancer, cell lines, and primary ascites cells express the human Mullerian inhibiting substance (MIS) Type II Receptor, bind, and are responsive to MIS. Clin Cancer Res 1999;5:3488-99; Hoshiya Y, et al. Mullerian inhibiting substance promotes interferon {gamma}-induced gene expression and apoptosis in breast cancer cells. J Biol Chem 2003;278:51703-12; Hoshiya Y, et al. Mullerian inhibiting substance induces NFkB signaling in breast and prostate cancer cells. Mol. Cell. Endocrinol. 2003;211:43-9. [1-3]]. We investigated the expression patterns of MISIIR in benign and malignant gynecologic tissues and benign non-gynecologic tissues to better assess the relevance of MISIIR as a target for new therapeutic and diagnostic approaches to gynecologic cancers. Secondarily, we examined the impact of MISIIR expression on overall survival (OS) and disease-free survival (DFS) in a cohort of epithelial ovarian cancers (EOC).

METHODS

Reverse-transcription polymerase chain reaction (RT-PCR), immunoblotting, and immunohistochemistry (IHC) were used to determine MISIIR expression. EOC cell lines (10), primary EOCs (12), and tissue microarrays (TMAs) containing benign gynecologic (179) and non-gynecologic tissues (25), EOC (182), endometrial carcinomas (109), uterine sarcomas (98), and ovarian dysgerminomas (22) were examined for MISIIR expression. Clinical data were collected for a cohort of 182 EOCs.

RESULTS

Ninety-two percent of primary EOCs and 44% of EOC cell lines expressed MISIIR mRNA. We observed moderate or strong MISIIR expression via IHC in the majority of gynecologic cancers: EOC 69% (125/182), ovarian dysgerminomas 77% (17/22), endometrial cancers 75% (82/109), uterine malignant mixed Müllerian tumors (MMMT) 59% (30/51), uterine leiomyosarcomas (LMS) 52% (15/29), and endometrial stromal sarcomas (ESS) 22% (4/18). Over 74% of normal non-gynecologic tissues did not express MISIIR. There was a significant correlation between MISIIR expression and improved OS (p=0.025, Chi square).

CONCLUSIONS

In the largest study to date, we report that MISIIR is highly expressed by a wide variety of gynecologic cancers, including cancers currently without effective systemic therapies. Low levels of expression in select non-gynecologic tissues coupled with high expression in gynecologic malignancies make MISIIR an attractive target for novel therapeutics and tumor-directed imaging in the management of gynecologic cancers. Further investigation into the impact of MISIIR expression and OS is also warranted.

Mullerian-inhibiting substance induces Gro-beta expression in breast cancer cells through a nuclear factor-kappaB-dependent and Smad1-dependent mechanism

Mullerian-inhibiting substance (MIS), a transforming growth factor-beta family member, activates the nuclear factor-kappaB (NF-kappaB) pathway and induces the expression of B-cell translocation gene 2 (BTG2), IFN regulatory factor-1 (IRF-1), and the chemokine Gro-beta. Inhibiting NF-kappaB activation with a phosphorylation-deficient IkappaBalpha mutant abrogated MIS-mediated induction of all three genes. Expression of dominant-negative Smad1, in which serines at the COOH-terminal SSVS motif are converted to alanines, suppressed MIS-induced Smad1 phosphorylation and impaired MIS-stimulated Gro-beta promoter-driven reporter expression and Gro-beta mRNA. Suppressing Smad1 expression using small interfering RNA also mitigated MIS-induced Gro-beta mRNA, suggesting that regulation of Gro-beta expression by MIS was dependent on activation of NF-kappaB as well as Smad1. However, induction of IRF-1 and BTG2 mRNAs by MIS was independent of Smad1 activation. Characterization of kappaB-binding sequences within Gro-beta, BTG2, and IRF-1 promoters showed that MIS stimulated binding of p50 and p65 subunits to all three sites, whereas phosphorylated Smad1 (phospho-Smad1) protein was detectable only in the NF-kappaB complex bound to the kappaB site of the Gro-beta promoter. Consistent with these observations, chromatin immunoprecipitation assays showed recruitment of both phospho-Smad1 and p65 to the Gro-beta promoter in vivo, whereas p65, but not phospho-Smad1, was recruited to the BTG2 promoter. These results show a novel interaction between MIS-stimulated Smad1 and NF-kappaB signaling in which enhancement of NF-kappaB DNA binding and gene expression by phospho-Smad1 is dependent on the sequence of the kappaB consensus site within the promoter.

Mullerian Inhibiting Substance enhances subclinical doses of chemotherapeutic agents to inhibit human and mouse ovarian cancer

Mullerian Inhibiting Substance (MIS), a biological modifier that causes regression of Mullerian ducts in male embryos, is effective as a single agent in vitro and in vivo against human and mouse ovarian cancer cell lines expressing MIS type II receptor; however, little is known about how recombinant human MIS (rhMIS), now being scaled for preclinical trials, could be used in combination with cytotoxic or targeted chemotherapeutic agents. Mouse serous and endometrioid ovarian carcinoma cell lines were tested in vitro against rhMIS alone and with doxorubicin, paclitaxel, or cisplatin as agents in clinical use. Because MIS releases FK506 binding protein (FKBP12), which activates the mammalian target of rapamycin (mTOR) downstream of Akt, rhMIS and rapamycin combinations were tested. MIS increases p16 protein levels, and 5'-Aza-2'-deoxycytidine (AzadC) induces p16 mRNA; therefore, they were used in combination in vitro and in vivo with a human ovarian cancer cell line. A paclitaxel-resistant human ovarian cancer cell line and its parental line both respond to rhMIS in vitro. Additivity, synergy, or competition was observed with MIS and rapamycin, AzadC, doxorubicin, cisplatin, and paclitaxel, suggesting that MIS in combination with selective targeted therapies might achieve greater activity against ovarian cancer than the use of each individual agent alone. These assays and statistical analyses could be useful in selecting rhMIS and chemotherapeutic agent combinations that enhance clinical efficacy and reduce toxicity.

Mullerian Inhibiting Substance Regulates Androgen-Induced Gene Expression and Growth in Prostate Cancer Cells through a Nuclear Factor-κB-Dependent Smad-Independent Mechanism

Mullerian inhibiting substance (MIS), a member of the TGFβ superfamily, causes regression of the Mullerian duct in male embryos. The presence of MIS type II and type I receptors in tissues and cell lines derived from the prostate suggests that prostate is a likely target for MIS. In this report, we demonstrate that MIS inhibits androgen-stimulated growth of LNCaP cells and decreases their survival in androgen-deprived medium by preventing cell cycle progression and inducing apoptosis. Expression of dominant-negative Smad1 reversed the ability of MIS to decrease LNCaP cell survival in androgen-deprived medium but not androgen-stimulated growth, whereas abrogation of nuclear factor-κB (NFκB) activation ablated the suppressive effects of MIS on both androgen-stimulated growth and androgen-independent survival. The effect of MIS on androgen-induced growth was not due to changes in androgen receptor expression. However, MIS suppressed androgen-stimulated transcription of prostate-specific antigen; ablation of NFκB activation reversed MIS-mediated suppression of prostate-specific antigen. These observations suggest that MIS regulates androgen-induced gene expression and growth in prostate cancer cells through a NFκB-dependent but Smad1-independent mechanism. Thus, MIS, in addition to potentially regulating prostate growth indirectly by suppressing testicular testosterone synthesis, may also be a direct regulator of androgen-induced gene expression and growth in the prostate at the cellular level.

Alternative splicing variants of IRF-1 lacking exons 7, 8, and 9 in cervical cancer

The two previously identified major splice variants of interferon regulatory factor 1 (IRF-1) do not appear to affect IRF-1-mediated gene activation. We searched for additional splice variants and examined their effect on wild-type IRF-1. RT-PCR experiments using normal and malignant human cervical tissue samples revealed five variants lacking some combination of exons 7, 8, and 9; their expression levels were higher in the malignant samples. These variants had predicted deletions of the functional domain or truncated protein isoforms, had different transcriptional activities, and attenuated transcriptional activity of IRF-1. Unlike the cell cycle-dependent IRF-1 transcript, the splice variant mRNA levels remained consistent throughout the cell cycle. The variant proteins were more stable than the IRF-1 protein, which may explain the strong inhibition of IRF-1 transcription in the presence of relatively small quantities of the alternative transcripts. In conclusion, alternative splicing in exons 7, 8, and 9 is an important mechanism for negatively regulating IRF-1 in cervical cancer.

Recombinant human Mullerian inhibiting substance inhibits long-term growth of MIS type II receptor-directed transgenic mouse ovarian cancers in vivo

PURPOSE

Mullerian inhibiting substance (MIS) is a glycoprotein hormone that causes Mullerian duct regression in male embryos. In short-term experiments, recombinant human MIS (rhMIS) inhibits xenotransplanted human ovarian cancer cell lines that are thought to be of Mullerian origin. Because this highly lethal cancer has a high recurrence rate after conventional chemotherapy, new treatments are warranted. We examined whether rhMIS as a novel, nontoxic, naturally occurring growth inhibitor can be an effective anticancer drug in long-term studies in vivo against allograft tumors that recapitulate human ovarian carcinoma.

EXPERIMENTAL DESIGN

Mouse ovarian carcinoma (MOVCAR) cell lines expressing the early region of the SV40 virus, including the large and small T-antigen genes under transcriptional control of a portion of the murine MIS receptor type II (MISRII) gene promoter, were derived from TgMISIIR-TAg transgenic mice. rhMIS was tested against MOVCAR cells in growth inhibition assays in vitro, and in vivo in 6-week-old female nude mice. Tumor growth in animals was measured at weekly intervals for up to 20 weeks.

RESULTS

MOVCAR cells and tumors express MISRII by Western blot, immunohistochemical, and Northern blot analyses. rhMIS significantly inhibited MOVCAR cell growth in vitro and in vivo in three separate long-term allotransplantation experiments.

CONCLUSIONS

Because rhMIS is an effective anticancer agent in in vitro and in long-term in vivo preclinical experiments against MISRII-positive tumors, we predict that rhMIS can be used safely and effectively to treat human ovarian malignancies.

Interferon regulatory factor-1 (IRF-1) exhibits tumor suppressor activities in breast cancer associated with caspase activation and induction of apoptosis

We have directly assessed the ability of interferon regulatory factor-1 (IRF-1) to act as a tumor suppressor gene in human breast cancer cells and explored whether this suppressor function is mechanistically conferred by affecting cell cycle transition, apoptosis and/or caspase activation. We have used a dual approach, measuring whether overexpression of wild-type IRF-1 or a dominant negative IRF-1 (dnIRF-1) produce opposing effects on breast cancer cell proliferation in vitro or tumorigenicity in athymic nude mice. Mechanistic studies determined the effects of blocking endogenous IRF-1 expression on cell cycle transition by flow cytometry, on apoptosis by Annexin V staining, and on caspase activation by fluorescent substrate cleavage. IRF-1 mRNA (P < or = 0.001) and protein (P < or = 0.001) are highly expressed in non-tumorigenic, normal, mammary epithelial cells, with intermediate expression in tumorigenic, but non-metastatic, cells and very low expression in metastatic cell lines. In MCF-7 cells transfected with a wild-type IRF-1 (MCF-7/IRF-1), IRF-1 mRNA expression inversely correlates with the rate of cell proliferation (r = -0.91; P = 0.002). Conversely, expression of dnIRF-1 in both MCF-7 (MCF-7/dnIRF-1; p53 wild-type) and T47D cells (T47D/dnIRF-1; p53 mutant) increases cell proliferation (P < or = 0.001). In athymic nude mice, the incidence of MCF-7/IRF-1 xenografts is reduced (P = 0.045), whereas MCF-7/dnIRF-1 xenografts exhibit a significantly higher tumor incidence (P < or = 0.001). Effects of IRF-1/dnIRF-1 are mediated through changes in the rates of apoptosis and not through cell cycle regulation. MCF-7/dnIRF-1 cells exhibit a 50% decrease in basal apoptosis (P = 0.007) and a significant reduction in caspase 8 activity (P = 0.03); similar effects occur in T47D/dnIRF-1 cells, where the effects on apoptosis appear to be mediated through inhibition of caspases 3/7 (P < 0.001) and caspase 8 (P = 0.03). These data establish a functional role for IRF-1 in the growth suppression of breast cancer cells and strongly implicate IRF-1 as a tumor suppressor gene in breast cancer that acts, independent of p53, to control apoptosis.

Interferon-regulatory factor-1 is critical for tamoxifen-mediated apoptosis in human mammary epithelial cells

Unlike estrogen receptor-positive (ER(+)) breast cancers, normal human mammary epithelial cells (HMECs) typically express low nuclear levels of ER (ER poor). We previously demonstrated that 1.0 microM tamoxifen (Tam) promotes apoptosis in acutely damaged ER-poor HMECs through a rapid, 'nonclassic' signaling pathway. Interferon-regulatory factor-1 (IRF-1), a target of signal transducer and activator of transcription-1 transcriptional regulation, has been shown to promote apoptosis following DNA damage. Here we show that 1.0 microM Tam promotes apoptosis in acutely damaged ER-poor HMECs through IRF-1 induction and caspase-1/3 activation. Treatment of acutely damaged HMEC-E6 cells with 1.0 microM Tam resulted in recruitment of CBP to the gamma-IFN-activated sequence element of the IRF-1 promoter, induction of IRF-1, and sequential activation of caspase-1 and -3. The effects of Tam were blocked by expression of siRNA directed against IRF-1 and caspase-1 inhibitors. These data indicate that Tam induces apoptosis in HMEC-E6 cells through a novel IRF-1-mediated signaling pathway that results in activated caspase-1 and -3.

Mullerian inhibiting substance suppresses tumor growth in the C3(1)T antigen transgenic mouse mammary carcinoma model

Mullerian inhibiting substance (MIS) inhibits breast cancer cell growth in vitro. To extend the use of MIS to treat breast cancer, it is essential to test the responsiveness of mammary tumor growth to MIS in vivo. Mammary tumors arising in the C3(1) T antigen mouse model expressed the MIS type II receptor, and MIS in vitro inhibited the growth of cells derived from tumors. Administration of MIS to mice was associated with a lower number of palpable mammary tumors compared with vehicle-treated mice (P=0.048), and the mean mammary tumor weight in the MIS-treated group was significantly lower compared with the control group (P=0.029). Analysis of proliferating cell nuclear antigen (PCNA) expression and caspase-3 cleavage in tumors revealed that exposure to MIS was associated with decreased proliferation and increased apoptosis, respectively, and was not caused by a decline in T antigen expression. The effect of MIS on tumor growth was also evaluated on xenografted human breast cancer cell line MDA-MB-468, which is estrogen receptor- and retinoblastoma-negative and expresses mutant p53, and thus complements the C3(1)Tag mouse mammary tumors that do not express estrogen receptor and have functional inactivation of retinoblastoma and p53. In agreement with results observed in the transgenic mice, MIS decreased the rate of MDA-MB-468 tumor growth and the gain in mean tumor volume in severe combined immunodeficient mice compared with vehicle-treated controls (P=0.004). These results suggest that MIS can suppress the growth of mammary tumors in vivo.

A novel approach in the treatment of neuroendocrine gastrointestinal tumors: additive antiproliferative effects of interferon-gamma and meta-iodobenzylguanidine

BACKGROUND

Therapeutic options to effectively inhibit growth and spread of neuroendocrine gastrointestinal tumors are still limited. As both meta-iodobenzylguanidine (MIBG) and interferon-gamma (IFNgamma) cause antineoplastic effects in neuroendocrine gastrointestinal tumor cells, we investigated the antiproliferative effects of the combination of IFNgamma and non-radiolabeled MIBG in neuroendocrine gut STC-1 and pancreatic carcinoid BON tumor cells.

METHODS AND RESULTS

IFNgamma receptors were expressed in both models. IFNgamma dose- and time-dependently inhibited the growth of both STC-1 and of BON tumor cells with IC50-values of 95 +/- 15 U/ml and 135 +/- 10 U/ml, respectively. Above 10 U/ml IFNgamma induced apoptosis-specific caspase-3 activity in a time-dependent manner in either cell line and caused a dose-dependent arrest in the S-phase of the cell cycle. Furthermore, IFNgamma induced cytotoxic effects in NE tumor cells. The NE tumor-targeted drug MIBG is selectively taken up via norepinephrine transporters, thereby specifically inhibiting growth in NE tumor cells. Intriguingly, IFNgamma treatment induced an upregulation of norepinephrine transporter expression in neuroendocrine tumors cells, as determined by semi-quantitative RT-PCR. Co-application of sub-IC50 concentrations of IFNgamma and MIBG led to additive growth inhibitory effects, which were mainly due to increased cytotoxicity and S-phase arrest of the cell cycle.

CONCLUSION

Our data show that IFNgamma exerts antiproliferative effects on neuroendocrine gastrointestinal tumor cells by inducing cell cycle arrest, apoptosis and cytotoxicity. The combination of IFNgamma with the NE tumor-targeted agent MIBG leads to effective growth control at reduced doses of either drug. Thus, the administration of IFNgamma alone and more so, in combination with MIBG, is a promising novel approach in the treatment of neuroendocrine gastrointestinal tumors.