Dienogest attenuates STAT3 activation in ovarian endometriotic cysts.

OBJECTIVE: Recent studies have suggested that endometriosis could be the result of excessive activation of signal transducer and activator of transcription 3 (STAT3), which is associated with the regulation of essential cellular mechanisms such as proliferation, invasion, and apoptosis. That finding implies that regulating STAT3 activation could play a key role in treating endometriosis. In the present study, we aimed to evaluate whether the anti-endometriotic effects of dienogest is mediated by the regulation of STAT3 activation. STUDY DESIGN: STAT3 activation was evaluated in normal endometrial and ovarian endometriotic tissues obtained from patients with/without preoperative dienogest treatment. A subsequent in vitro analysis with endometriotic cyst stromal cells (ECSCs) was used to confirm the direct influence of dienogest in STAT3 activation. RESULT: STAT3 activation is significantly higher in endometriotic tissues from non-treated patients than in normal endometrial tissues, and that difference is reversed by preoperative administration of dienogest. Similarly, the inhibitory effects of dienogest on STAT3 activation are demonstrated by in vitro results showing that dienogest treatment significantly inhibits IL-6-stimulated STAT3 activation in cultured ECSCs. That inhibition was accompanied by decreased expression of proliferative (PCNA), invasive (MMP-2), and anti-apoptotic (BCL-2) proteins. Furthermore, downregulating STAT3 activity with siRNA decreased PCNA, MMP-2, and BCL-2 expression in IL-6-treated ECSCs. CONCLUSION: Dienogest inhibits STAT3 activation in ECSCs, which affects their proliferation, invasiveness, and apoptosis.

Inhibition of the NLRP3 inflammasome by progesterone is attenuated by abnormal autophagy induction in endometriotic cyst stromal cells: implications for endometriosis.

The NOD-like receptor pyrin domain containing 3 (NLRP3) inflammasome is a cytosolic multi-protein complex that induces inflammation and is known to be regulated negatively by autophagy. Previous studies reported an abnormal induction of autophagy linked to progesterone resistance in human endometriotic cells. Therefore, an aberrant autophagy induction response to progesterone might contribute to the altered inflammatory response observed in endometriotic tissues. To evaluate this hypothesis, we elucidate whether regulation of the NLRP3 inflammasome by ovarian steroids is mediated by autophagy in human endometrial stromal cells (normal endometrial stromal cells (NESCs)) from patients with uterine leiomyoma (presumed normal) and whether abnormal autophagy induction in endometriotic cyst stromal cells (ECSCs) affects NLRP3 inflammasome-induced interleukin-1ß (IL-1ß) production. Our results show that estrogen enhanced NLRP3 inflammasome activation in NESCs, resulting in increased IL-1ß production. Progesterone decreased NLRP3 inflammasome activity with an increase in autophagy induction in estrogen-treated NESCs. Inhibition of NLRP3 inflammasome activity by progesterone was blocked by autophagy inhibition. However, progesterone failed to change NLRP3 inflammasome activity and autophagy induction in estrogen-treated ECSCs. In contrast, dienogest, a specific progesterone receptor agonist, reduced NLRP3 inflammasome-mediated IL-1ß production through autophagy induction in ECSCs. Furthermore, autophagy induction was decreased and NLRP3 inflammasome activity was increased in endometriotic tissues, which was reversed by preoperative administration of dienogest. In conclusion, our results suggest that progesterone inhibits NLRP3 inflammasome activation through autophagy in endometrial stromal cells. However, this inhibitory effect is attenuated in endometriotic stromal cells due to an aberrant autophagic response to progesterone, which could lead to an altered inflammatory response in endometriosis.

Nuclear factor-kappa B signaling in endometriotic stromal cells is not inhibited by progesterone owing to an aberrant endoplasmic reticulum stress response: a possible role for an altered inflammatory process in endometriosis.

Endoplasmic reticulum (ER) stress serves as a key modulator of the inflammatory response by controlling nuclear factor-kappaB (NF-κB) signaling. Previous studies from our laboratory have reported an abnormal induction of ER stress linked to progesterone resistance in human endometriotic cells. Therefore, an aberrant ER stress response to progesterone might contribute to the altered inflammatory response observed in endometriotic tissues. To evaluate this hypothesis, we investigated whether ER stress is involved in regulation of NF-κB in endometrial stromal cells and whether induction of aberrant ER stress in endometriotic stromal cells affects pro-inflammatory cytokine production. We found that tunicamycin-induced ER stress inhibited NF-κB activation and pro-inflammatory cytokine (IL-6 and COX2) production in TNF-α- or IL-1ß-treated normal endometrial stromal cells (NECSs). Tunicamycin increased the expression of A20 and C/EBPß, which are negative regulators of NF-κB, and this increase inhibited NF-κB activity in NESCs incubated with TNF-α or IL-1ß. Similarly, progesterone increased A20 and C/EBPß expression through upregulation of ER stress in NESCs, resulting in inhibition of NF-κB activity and IL-6 and COX2 production. However, progesterone had no significant effects on induction of ER stress, A20 or C/EBPß expression, NF-κB activity or IL-6 or COX2 production in ovarian endometriotic cyst stromal cells (ECSCs). In contrast, upregulation of ER stress by tunicamycin significantly reduced IL-6 and COX2 production by inhibiting NF-κB activity in ECSCs. In conclusion, our results suggest that NF-κB activity in endometriotic stromal cells was not inhibited because of an aberrant ER stress response to progesterone, resulting in an increase in pro-inflammatory cytokine production.

Dienogest regulates apoptosis, proliferation, and invasiveness of endometriotic cyst stromal cells via endoplasmic reticulum stress induction.

Dienogest, a specific progesterone receptor agonist, is used in the treatment of endometriosis. However, it is still unclear as to the mechanisms of therapeutic effects on endometriosis. Our recent study showed that endometriosis may be the result of aberrant endoplasmic reticulum (ER) stress induction due to progesterone resistance. This finding suggests that the regulation of ER stress induction may play a key role in treatment of endometriosis. Therefore, the anti-endometriotic effects of dienogest may be mediated by regulation of ER stress. To test this hypothesis, we elucidate whether dienogest affects endometriotic stromal cell apoptosis, proliferation and invasiveness by modulating ER stress-induced CCAAT/enhancer-binding protein homologous protein (CHOP) expression. Specifically, PRKR-like ER kinase (PERK)/eukaryotic initiation factor 2α (eIF2α)/activating transcription factor 4 (ATF4), inositol-requiring kinase 1 (IRE1)/TNF receptor-associated factor 2 (TRAF2)/apoptosis signal-regulating kinase 1 (ASK1)/c-Jun N-terminal kinase (JNK) signaling, and downstream CHOP were evaluated to determine the involved ER stress-mediated regulation mechanism of CHOP expression. Our results show that progesterone treatment did not have any significant effects on ER stress, apoptosis, proliferation, and invasion in estrogen-treated endometriotic cyst stromal cells (ECSCs). However, dienogest treatment upregulated the induction of ER stress. It also led to increased apoptosis, and decreased proliferation and invasiveness. These dienogest-induced changes in apoptosis, proliferation and invasiveness were reversed by the ER stress inhibitor salubrinal. Furthermore, dienogest-induced ER stress increased CHOP expression through activation of both PERK/elf2α/ATF4 and IRE1/TRAF2/ASK1/JNK signaling. This upregulation was blocked by transfection with PERK and IRE1 siRNA, which decreased apoptosis and increased the proliferation and invasiveness of dienogest-treated ECSCs. Taken together, our findings indicate that dienogest enhances ER stress induction in endometriotic stromal cells, which affects apoptosis, proliferation and invasiveness via CHOP upregulation.

Involvement of endoplasmic reticulum stress in regulation of endometrial stromal cell invasiveness: possible role in pathogenesis of endometriosis.

Endoplasmic reticulum (ER) stress is known to reduce invasiveness in some cancer cells by inhibiting the AKT/mTOR pathway. A previous study from our laboratory suggested that ER stress is promoted by progesterone in human endometrial cells, which suggests that progesterone may inhibit endometrial cell invasiveness by up-regulating ER stress. Therefore, aberrant ER stress in response to progesterone may contribute to the altered invasiveness found in endometriotic tissues. To test this hypothesis, we elucidate whether ER stress is involved in regulation of human endometrial cell invasiveness through the AKT/mTOR pathway and if this involvement is associated with altered invasiveness in endometriotic cells. Specifically, we sought to determine the effects of ER stress on AKT/mTOR pathway by evaluating ER stress-mediated CHOP/TRIB3 signaling, a negative regulator of AKT. We found that ER stress marker GRP78 expression increased with CHOP and TRIB3 expression in normal endometrial stromal cells (NESCs) treated with tunicamycin, and this increase was accompanied by decreased AKT and mTOR activity and cellular invasiveness. Similarly, progesterone increased GRP78, CHOP and TRIB3 expression in NESCs. Subsequently, inhibition of AKT and mTOR activity decreased cellular invasiveness. This progesterone-induced decrease in cellular invasiveness was reversed by inhibition of ER stress. In contrast, progesterone did not change CHOP, TRIB3, AKT, mTOR or invasiveness in endometriotic cyst stromal cells. In contrast to normal endometrium, endometriotic tissues showed no changes in CHOP, TRIB3 and invasion-related proteins (MMP2 and MMP9) expression throughout the menstrual cycle. Taken together, our findings indicate that abnormal ER stress response to progesterone increased endometriotic stromal cell invasiveness via the AKT/mTOR pathway.

Aberrant PTEN expression in response to progesterone reduces endometriotic stromal cell apoptosis

In some human cancer cells, PTEN (phosphatase and tensin homolog deleted on chromosome 10) is known to regulate autophagy induction positively through the inhibition of PI3K/AKT pathway, leading to the activation of mTOR, a major negative regulator of autophagy. Recent studies reported that PTEN expression is abnormally decreased in endometriotic lesions. In endometriosis, abnormal PTEN expression may contribute to the alteration of endometrial cell autophagy, which may affect apoptosis because endometrial cell autophagy is directly involved in the regulation of apoptosis. To test this hypothesis, we evaluated the involvement of PTEN in the regulation of autophagy induction in human normal endometrial stromal cells (NESCs). In addition, we sought to determine whether aberrant PTEN expression in endometriotic cyst stromal cells (ECSCs) is associated with autophagy dysregulation, and a subsequent decrease in apoptosis. Our results show that PTEN expression was enhanced by progesterone treatment in NESCs. Subsequently, autophagy and apoptosis induction increased through the inhibition of AKT and mTOR activity. This progesterone-induced increase in apoptosis was reversed by the inhibition of autophagy induction using either mifepristone (progesterone receptor modulator) or PTEN inhibitor. In contrast, progesterone had no significant effects on PTEN expression, AKT, mTOR activity, autophagy or apoptosis in ECSCs. Furthermore, in contrast to normal eutopic endometrium, endometriotic tissues have constant PTEN expression, autophagy and apoptosis throughout the menstrual cycle. In conclusion, our results suggest abnormal PTEN expression in response to progesterone was observed in ECSCs, which led to the dysregulation of autophagy induction via AKT/mTOR signalling and a subsequent decrease in apoptosis.

Dienogest enhances autophagy induction in endometriotic cells by impairing activation of AKT, ERK1/2, and mTOR.

OBJECTIVE: To elucidate the therapeutic mechanisms of progestin and the effects of progesterone and progestin (dienogest) on autophagy induction and regulation in endometriotic cells, specifically the effects of progesterone and dienogest on the phosphoinositide-3/protein kinase B (PI3K-AKT) and mitogen-activated protein kinase kinases 1 and 2 (MEK1/2)/extracellular-signal-regulated kinase 1/2 (ERK1/2) pathways, which activate mammalian target of rapamycin (mTOR), a major negative regulator of autophagy. DESIGN: In vitro study using human endometriotic cyst stromal cells (ECSCs). SETTING: University medical center. PATIENT(S): Fifteen patients with ovarian endometrioma. INTERVENTION(S): ECSCs treated with progesterone or dienogest. MAIN OUTCOME MEASURE(S): Autophagy as measured by the expression of the microtubule-associated protein light chain 3-II (LC3-II) and autophagosome formation, and levels of AKT, ERK1/2, and mTOR activity to quantify the phosphorylation of AKT, ERK1/2, and S6K (the downstream target of mTOR). RESULT(S): Progesterone treatment had not statistically significant effect on LC3-II expression, autophagosome formation, or phosphorylation of AKT, ERK1/2, or S6K in estrogen-treated ECSCs. However, dienogest treatment up-regulated LC3-II expression and stimulated autophagosome formation. These effects were accompanied by decreased activation of AKT, ERK1/2, and S6K. Furthermore, incubation of ECSCs with AKT and ERK1/2 inhibitors, which mimicked dienogest-mediated inhibition of AKT and ERK1/2 activity, suppressed S6K activity, followed by an increase in LC3-II expression. In addition, cotreatment with dienogest and 3-methyladenine (autophagy inhibitor) decreased the levels of apoptosis of ECSCs compared with the single treatment with dienogest. CONCLUSION(S): Our results suggest that dienogest treatment of endometriotic cells suppresses AKT and ERK1/2 activity, thereby in turn inhibiting mTOR, inducing autophagy, and promoting apoptosis.

ERK1/2 is involved in luteal cell autophagy regulation during corpus luteum regression via an mTOR-independent pathway.

Autophagy is known to be regulated by the phosphoinositide-3 kinase (PI3K)-protein kinase B (AKT) and/or mitogen-activated protein kinase 1/2 (MEK1/2)-extracellular signal-regulated kinase 1/2 (ERK1/2) pathways, leading to activation of mammalian target of rapamycin (mTOR), a major negative regulator of autophagy. However, some reports have also suggested that autophagic regulation by the PI3K-AKT and/or MEK1/2-ERK1/2 pathways may not be mediated by mTOR activity, and there is no direct evidence of the involvement of these pathways in luteal cell autophagy regulation. To elucidate the luteal cell-specific regulatory mechanisms of autophagy induction during corpus luteum (CL) regression, we evaluated whether luteal cell autophagy is regulated by the PI3K-AKT pathway and/or MEK1/2-ERK1/2 pathway and if this regulation is mediated by mTOR. We found that autophagy induction increased despite mTOR activation in luteal cells cultured with prostaglandin F2α (PGF2α), an important mediator of CL regression, suggesting that PGF2α-induced autophagy is independent of mTOR regulation. We also found that PGF2α-induced autophagy was not mediated by AKT activity, because AKT inhibition using a PI3K inhibitor (wortmannin) did not change autophagy induction or mTOR activity. In contrast, ERK1/2 activity increased in PGF2α-treated luteal cells, as did the levels of autophagy induction despite increased mTOR activity. Furthermore, PGF2α-mediated up-regulation of luteal cell autophagy was reversed by addition of ERK1/2 inhibitors, despite a decrease in mTOR activity. These in vitro results suggest that luteal cell autophagy is induced by increased ERK1/2 activity during CL regression, and is independent of mTOR activity. This finding was further supported by in vivo experiments in a pseudo-pregnant rat model, which showed that induction of luteal cell autophagy increased during luteal stage progression and that this was accompanied by increased ERK1/2 and mTOR activity. Taken together, our findings indicate that activation of ERK1/2 is a key event in the induction of luteal cell autophagy during CL regression which is not associated with mTOR regulation.

Differential induction of autophagy by mTOR is associated with abnormal apoptosis in ovarian endometriotic cysts.

Mammalian target of rapamycin (mTOR) is known to be a major negative regulator of autophagy. Recent studies have shown that mTOR activity is abnormally increased in endometriotic lesions. In endometriosis, abnormal mTOR activity may contribute to the alteration of endometrial cell autophagy, which may affect apoptosis because endometrial cell autophagy is directly involved in the regulation of apoptosis. To test this hypothesis, we investigated whether endometrial cell autophagy is altered by aberrant mTOR activity and is associated with apoptosis in ovarian endometriotic cysts. Our results show that endometrial cell autophagy induction was increased by mTOR inhibition as the menstrual cycle progresses in the normal endometrium, and that it is correlated with apoptosis. However, in endometriotic tissues from ovarian endometriotic cysts, autophagy, mTOR activity and apoptosis were constant throughout the menstrual cycle, suggesting that a constant level of autophagy is maintained by disinhibition of mTOR activity during the menstrual cycle in endometriotic tissues and is related to decreased apoptosis. Indeed, compared with normal endometrium, increased mTOR activity during the secretory phase in endometriotic tissues inhibited autophagy and apoptosis induction. In addition, to determine the direct effect of autophagy induction mediated by mTOR on endometriotic cell apoptosis, endometriotic cells were treated with rapamacin (mTOR inhibitor) with and without 3-methyladenine (3-MA, autophagy inhibitor). Although rapamycin treatment induced autophagy and led to apoptosis promotion, the pro-apoptotic effect of rapamycin was reversed by the addition of 3-MA, suggesting that mTOR inhibition promotes endometriotic cell apoptosis via autophagy induction. In conclusion, our results suggest that aberrant mTOR activity in ovarian endometriotic cysts leads to alteration of endometrial cell autophagy, which is associated with abnormal apoptosis.

AKT is involved in granulosa cell autophagy regulation via mTOR signaling during rat follicular development and atresia.

In this study, we examined whether granulosa cell autophagy during follicular development and atresia was regulated by the class I phosphoinositide-3 kinase/protein kinase B (AKT) pathway, which is known to control the activity of mammalian target of rapamycin (mTOR), a major negative regulator of autophagy. Ovaries and granulosa cells were obtained using an established gonadotropin-primed immature rat model that induces follicular development and atresia. Autophagy was evaluated by measuring the expression level of microtubule-associated protein light chain 3-II (LC3-II) using western blots and immunohistochemistry. The activity of AKT and mTOR was also examined by observing the phosphorylation of AKT and ribosomal protein S6 kinase (S6K) respectively. After gonadotropin injection, LC3-II expression was suppressed and phosphorylation of AKT and S6K increased in rat granulosa cells. By contrast, gonadotropin withdrawal by metabolic clearance promoted LC3-II expression and decreased phosphorylation of AKT and S6K. In addition, in-vitro FSH treatment of rat granulosa cells also indicated inhibition of LC3-II expression accompanied by a marked increase in phosphorylation of AKT and S6K. Inhibition of AKT phosphorylation using AKT inhibitor VIII suppressed FSH-mediated phosphorylation of S6K, followed by an increase in LC3-II expression. Furthermore, co-treatment with FSH and AKT inhibitor increased the levels of apoptosis and cell death of granulosa cells compared with the single treatment with FSH. Taken together, our findings indicated that AKT-mediated activation of mTOR suppresses granulosa cell autophagy during follicular development and is involved in the regulation of apoptotic cell death.

The role of autophagy in human endometrium.

Autophagy appears to play an important role in the normal development and maintenance of homeostasis in a variety of tissues, including the female reproductive tract. However, the role of autophagy and the association between autophagy and apoptosis in cyclic remodeling of the human endometrium have not been described. Therefore, we investigated the involvement of autophagy during the human endometrial cycle and its association with apoptosis. Endometrial samples were obtained from 15 premenopausal, nonpregnant women who underwent hysterectomies for benign gynecological reasons. The autophagy-associated protein, microtubule-associated protein 1 light chain 3 alpha (MAP1LC3A), was immunolocalized, and its expression level was measured by Western blot analysis. Apoptosis was evaluated by measuring the expression level of cleaved caspase 3 protein. MAP1LC3A protein was primarily expressed within the endometrial glandular cells and increased during the secretory phase. The expression level of the membrane-bound form of MAP1LC3A (MAP1LC3A-II) also increased as the menstrual cycle progressed, reaching a maximum level during the late secretory phase. This pattern coincided with the expression of cleaved caspase 3. Furthermore, expression of MAP1LC3A-II and cleaved caspase 3 increased in the in vitro-cultured endometrial cancer cells when estrogen and/or progesterone were withdrawn from the culture media to mimic physiological hormonal changes. These findings suggest that endometrial cell autophagy is directly involved in the cyclic remodeling of the human endometrium and is correlated with apoptosis. In addition, we inhibited autophagic processes using 3-methyladenine (3-MA) or bafilomycin A1 (Baf A1) to evaluate the role of autophagy in apoptosis induction in endometrial cancer cells. While the inhibition of autophagosome formation using 3-MA did not decrease apoptosis or cell death, the inhibition of autophagosome degradation by fusion with lysosomes using Baf A1 increased apoptosis and cell death, suggesting that the accumulation of autophagosomes induces apoptosis. Furthermore, Baf A1-induced apoptotic cell death was decreased by the apoptosis inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (Z-VAD-FMK). In conclusion, these results indicate that autophagy is involved in the endometrial cell cycle affecting apoptosis and is most prominent during the late secretory phase.

The role of autophagy in corpus luteum regression in the rat.

Autophagy is associated with luteal cells death during regression of the corpus luteum (CL) in some species. However, the involvement of autophagy or the association between autophagy and apoptosis in CL regression are largely unknown. Therefore, we investigated the role of autophagy in CL regression and its association with apoptosis. Ovaries were obtained from pseudopregnant rats at Days 2 (early), 7 (mid-), and 14 and 20 (late-luteal stage) of the pseudopregnancy; autophagy-associated protein (microtuble-associated protein light chain 3 [LC3]) was immunolocalized and its expression level was measured. Luteal cell apoptosis was evaluated by measuring cleaved caspase 3 expression. LC3 expression increased slightly from early to mid-luteal stage, with maximal levels detected at the late-luteal stage in steroidogenic luteal cells. The expression level of the membrane form of LC3 (LC3-II) also increased during luteal stage progression, and reached a maximum at the end point of late-luteal stage (Day 20). This pattern coincided with cleaved caspase 3 expression. Furthermore, LC3-II expression increased, as did levels of cleaved caspase 3 in luteal cells cultured with prostaglandin F(2alpha) known to induce CL regression. These findings suggest that luteal cell autophagy is directly involved in CL regression, and is correlated with increased apoptosis. In addition, autophagic processes were inhibited using 3-methyladenine or bafilomycin A1 to evaluate the role of autophagy in apoptosis induction. Inhibition of autophagosome degradation by fusion with lysosomes (bafilomycin A1) increased apoptosis and cell death. Furthermore, inhibition of autophagosome formation (3-methyladenine) decreased apoptosis and cell death, suggesting that the accumulation of autophagosomes induces luteal cell apoptosis. In conclusion, these results indicate that autophagy is involved in rat luteal cell death through apoptosis, and is most prominent during CL regression.

AGR2, a mucinous ovarian cancer marker, promotes cell proliferation and migration.

Ovarian cancer is a leading cause of death in women. Early detection of ovarian cancer is essential to decrease mortality. However, the early diagnosis of ovarian cancer is difficult due to a lack of clinical symptoms and suitable molecular diagnostic markers. Thus, identification of meaningful tumor biomarkers with potential clinical application is clearly needed. To search for a biomarker for the early detection of ovarian cancer, we identified human anterior gradient 2 (AGR2) from our systematic analysis of paired normal and ovarian tumor tissue cDNA microarray. We noted a marked overexpression of AGR2 mRNA and protein in early stage mucinous ovarian tumors compared to normal ovarian tissues and serous type ovarian tumors by Western blot analysis and immunohistochemistry. To further elucidate the role of AGR2 in ovarian tumorigenesis, stable 2774 human ovarian cancer cell lines overexpressing AGR2 were established. Forced expression of AGR2 in 2774 cells enhanced the growth and migration of ovarian cancer cells. AGR2 protein was detected in the serum of mucinous ovarian cancer patients by Western blot and ELISA analysis. Thus, AGR2 is a potential biomarker for the diagnosis of mucinous ovarian cancer and an ELISA assay may facilitate the early detection of mucinous ovarian cancer using patient serum.

Induction of apoptotic cell death via accumulation of autophagosomes in rat granulosa cells.

This study evaluated the effect of autophagosome accumulation on apoptotic cell death in granulosa cells from developing follicles. Our results indicate that the accumulation of autophagosomes induces apoptotic cell death of granulosa cells through decreased bcl-2 expression and subsequent caspase activation.

Dkk3, downregulated in cervical cancer, functions as a negative regulator of beta-catenin.

The Wnt/beta-catenin signaling pathway is activated during the malignant transformation of keratinocytes that originate from the human uterine cervix. Dkk1, 2 and 4 have been shown to modulate the Wnt-induced stabilization of the beta-catenin signaling pathway. However, the function of Dkk3 in this pathway is unknown. Comparison of the Dkk3 gene expression profiles in cervical cancer and normal cervical tissue by cDNA microarray and subsequent real-time PCR revealed that the Dkk3 gene is frequently downregulated in the cancer. Methylation studies showed that the promoter of Dkk3 was methylated in cervical cancer cell lines and 22 (31.4%) of 70 cervical cancer tissue specimens. This promoter methylation was associated with reduced expression of Dkk3 mRNA in the paired normal and tumor tissue samples. Further, the reintroduction of Dkk3 into HeLa cervical cancer cells resulted in reduced colony formation and retarded cell growth. The forced expression of Dkk3 markedly attenuated beta-catenin-responsive luciferase activity in a dose-dependent manner and decreased the beta-catenin levels. By utilizing a yeast two-hybrid screen, betaTrCP, a negative regulator of beta-catenin was identified as a novel Dkk3-interacting partner. Coexpression with betaTrCP synergistically enhanced the inhibitory function of Dkk3 on beta-catenin. The stable expression of Dkk3 blocks the nuclear translocation of beta-catenin, resulting in downregulation of its downstream targets (VEGF and cylcin D), whereas knockdown of Dkk3 abrogates this blocking. We conclude from our finding that Dkk3 is a negative regulator of beta-catenin and its downregulation contribute to an activation of the beta-catenin signaling pathway.

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.