Autophagy orchestrates adaptive responses to targeted therapy in endometrial cancer.

Targeted therapies in endometrial cancer (EC) using kinase inhibitors rarely result in complete tumor remission and are frequently challenged by the appearance of refractory cell clones, eventually resulting in disease relapse. Dissecting adaptive mechanisms is of vital importance to circumvent clinical drug resistance and improve the efficacy of targeted agents in EC. Sorafenib is an FDA-approved multitarget tyrosine and serine/threonine kinase inhibitor currently used to treat hepatocellular carcinoma, advanced renal carcinoma and radioactive iodine-resistant thyroid carcinoma. Unfortunately, sorafenib showed very modest effects in a multi-institutional phase II trial in advanced uterine carcinoma patients. Here, by leveraging RNA-sequencing data from the Cancer Cell Line Encyclopedia and cell survival studies from compound-based high-throughput screenings we have identified the lysosomal pathway as a potential compartment involved in the resistance to sorafenib. By performing additional functional biology studies we have demonstrated that this resistance could be related to macroautophagy/autophagy. Specifically, our results indicate that sorafenib triggers a mechanistic MAPK/JNK-dependent early protective autophagic response in EC cells, providing an adaptive response to therapeutic stress. By generating in vivo subcutaneous EC cell line tumors, lung metastatic assays and primary EC orthoxenografts experiments, we demonstrate that targeting autophagy enhances sorafenib cytotoxicity and suppresses tumor growth and pulmonary metastasis progression. In conclusion, sorafenib induces the activation of a protective autophagic response in EC cells. These results provide insights into the unopposed resistance of advanced EC to sorafenib and highlight a new strategy for therapeutic intervention in recurrent EC.

Bioluminescence Imaging to Monitor the Effects of the Hsp90 Inhibitor NVP-AUY922 on NF-κB Pathway in Endometrial Cancer.

PURPOSE: In this study, we first aimed to evaluate the effects in vitro and in vivo, of the Hsp90 inhibitor NVP-AUY922, in endometrial cancer (EC). We also aimed to track nuclear factor kappa B (NF-κB) signalling, a key pathway involved in endometrial carcinogenesis and to check whether NVP-AUY922 treatment modulates it both in vitro and in vivo. PROCEDURES: I n vitro effects of NVP-AUY922 on EC cell growth and the signalling pathways were assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), clonogenic assays, Western Blot and luciferase assay. NVP-AUY922 effect on Ishikawa (IK) xenograft growth was evaluated in vivo, and NF-κB activity was monitored using bioluminescence imaging. RESULTS: NVP-AUY922 inhibited the growth of three endometrial cell lines tested in vitro. In vivo, NVP-AUY922 reduced tumour growth of 47 % (p = 0.042) compared to control condition. Moreover, the bioluminescence signal of the tumours harbouring IK NF-κB-LUC cells was significantly reduced in NVP-AUY922-treated animals compared to untreated ones. CONCLUSIONS: NVP-AUY922 reduced EC tumour growth and NF-κB signalling both in vitro and in vivo. As therapeutic resistance of EC remains a challenge for oncologists nowadays, we think that NVP-AUY922 represents a valid alternative to conventional chemotherapy, and we believe that this approach for assessing and tracking the activation of NF-κB pathway may be of therapeutic benefit.

Role of local bioactivation of vitamin D by CYP27A1 and CYP2R1 in the control of cell growth in normal endometrium and endometrial carcinoma.

Vitamin D (VD) deficiency has been suggested as a risk factor for cancer. One recognized mechanism is that the low-serum 25-hydroxyvitamin D (25(OH)D) of VD deficiency reduces intratumoral 25(OH)D conversion to 1α,25-dihydroxyvitamin D (1,25D, the hormonal form of VD), compromising 1,25D-VD receptor (VDR) antitumoral actions. Reduced tumoral VDR and increased CYP24A1, the enzyme that degrades 1,25D and 25(OH)D, further worsen cancer progression. Importantly, in cells expressing CYP27A1 and/or CYP2R1, which convert inert VD into 25(OH)D, low-serum VD may reduce intratumoral 25(OH)D synthesis thereby compromising VDR antitumoral actions because 25(OH)D can activate the VDR directly and enhance 1,25D-VDR action. Therefore, this study examined whether abnormal endometrial expression of CYP27A1 and/or CYP2R1 may impair VDR-antiproliferative properties in endometrial carcinoma (EC). Immunohistochemical analysis of tissue microarrays of normal human endometrium (NE; n=60) and EC (n=157) showed the expected lower VDR expression in EC (P=0.0002). Instead, CYP24A1 expression was lower in EC compared with NE, while CYP27A1 and CYP2R1 expressions were higher (P=0.0002; P=0.03). Furthermore, in NE and EC, CYP2R1 and CYP27A1 expression correlated directly with nuclear VDR levels, an indicator of ligand-induced VDR activation, and inversely with the proliferation marker Ki67. Accordingly, in the endometrioid carcinoma cell lines IK, RL95/2 and HEC1-A, which express VDR, CYP27A1, and CYP2R1, VD efficaciously reduced cell viability and colony number, with a time course that paralleled actual increases in both intracellular 25(OH)D and nuclear VDR levels. Thus, VD may protect from EC progression in part through increased intratumoral 25(OH)D production by CYP27A1 and CYP2R1 for autocrine/paracrine enhancement of 1,25D-VDR-antiproliferative actions.

Antioxidants impair anti-tumoral effects of Vorinostat, but not anti-neoplastic effects of Vorinostat and caspase-8 downregulation.

We have recently demonstrated that histone deacetylase inhibitor, Vorinostat, applied as a single therapy or in combination with caspase-8 downregulation exhibits high anti-tumoral activity on endometrial carcinoma cell lines. In the present study, we have assessed the signalling processes underlying anti-tumoral effects of Vorinostat. Increasing evidence suggests that reactive oxygen species are responsible for histone deacetylase inhibitor-induced cell killing. We have found that Vorinostat induces formation of reactive oxygen species and DNA damage. To investigate the role of oxidative stress as anti-neoplastic mechanism, we have evaluated the effects of different antioxidants (Bha, Nac and Tiron) on endometrial carcinoma cell line Ishikawa treated with Vorinostat. We show that Bha, Nac and Tiron markedly inhibited the cytotoxic effects of Vorinostat, increasing cell viability in vitro. We found that all three antioxidants did not inhibited accumulation of acetyl Histone H4, so that antioxidants did not inhibit Vorinostat activity. Finally, we have evaluated the effects of antioxidants on anti-tumoral activity of Vorinostat as monotherapy or in combination with caspase-8 downregulation in vivo. Interestingly, antioxidants blocked the reduction of tumour growth caused by Vorinostat, but they were unable to inhibit anti-tumoral activity of Vorinostat plus caspase-8 inhibition.

Long-term estradiol exposure is a direct mitogen for insulin/EGF-primed endometrial cells and drives PTEN loss-induced hyperplasic growth.

Loss of tumor-suppressor PTEN is the most common alteration in endometrial carcinoma. However, the relationship between loss of PTEN, growth factors [eg, insulin/insulin-like growth factor (IGF)-1], epidermal growth factor (EGF), and hyperestrogenism in the development of endometrial carcinoma is still controversial. By using three-dimensional (3D) cultures of PTEN(+/+) and PTEN(+/-) endometrial epithelial cells, we investigated the effects of EGF, insulin/IGF, and estradiol in endometrial cell proliferation. We have previously demonstrated that 3D cultures of endometrial cells require EGF and insulin/IGF to proliferate. Herein, we demonstrate that, in the presence of EGF and insulin/IGF, long-term estradiol treatment directly induces proliferation of 3D cultures. Moreover, we show that the mitogenic effects of estradiol require the presence of insulin/IGF and EGF, because withdrawal of such factors completely abolishes estradiol-induced proliferation. In the presence of EGF and insulin/IGF, PTEN(+/-) and PTEN(+/+) spheroids display a similar rate of proliferation. However, the addition of estradiol causes an exaggerated proliferation of PTEN(+/-) cultures, leading to formation of complex structures, such as those observed in endometrial hyperplasia or carcinoma. In summary, we demonstrate that EGF and insulin/IGF prime endometrial epithelial cells to direct the mitogenic effects of estradiol. Furthermore, PTEN deficiency results in enhanced responsiveness to this combination, leading to the development of hyperplasia of endometrial cells in culture.

Combination of Vorinostat and caspase-8 inhibition exhibits high anti-tumoral activity on endometrial cancer cells.

Histone deacetylase inhibitors such as Vorinostat display anti-neoplastic activity against a variety of solid tumors. Here, we have investigated the anti-tumoral activity of Vorinostat on endometrial cancer cells. We have found that Vorinostat caused cell growth arrest, loss of clonogenic growth and apoptosis of endometrial cancer cells. Vorinostat-induced the activation of caspase-8 and -9, the initiators caspases of the extrinsic and the intrinsic apoptotic pathways, respectively. Next, we investigated the role of the extrinsic pathway in apoptosis triggered by Vorinostat. We found that Vorinostat caused a dramatic decrease of FLIP mRNA and protein levels. However, overexpression of the long from of FLIP did not block Vorinostat-induced apoptosis. To further investigate the role of extrinsic apoptotic pathway in Vorinostat-induced apoptosis, we performed an shRNA-mediated knock-down of caspase-8. Surprisingly, downregulation of caspase-8 alone caused a marked decrease in clonogenic ability and reduced the growth of endometrial cancer xenografts in vivo, revealing that targeting caspase-8 may be an attractive target for anticancer therapy on endometrial tumors. Furthermore, combination of caspase-8 inhibition and Vorinostat treatment caused an enhancement of apoptotic cell death and a further decrease of clonogenic growth of endometrial cancer cells. More importantly, combination of Vorinostat and caspase-8 inhibition caused a nearly complete inhibition of tumor xenograft growth. Finally, we demonstrate that cell death triggered by Vorinostat alone or in combination with caspase-8 shRNAs was inhibited by the anti-apoptotic protein Bcl-XL. Our results suggest that combinatory therapies using Vorinostat treatment and caspase-8 inhibition can be an effective treatment for endometrial carcinomas.

An inducible knockout mouse to model the cell-autonomous role of PTEN in initiating endometrial, prostate and thyroid neoplasias.

PTEN is one of the most frequently mutated tumor suppressor genes in human cancers. The role of PTEN in carcinogenesis has been validated by knockout mouse models. PTEN heterozygous mice develop neoplasms in multiple organs. Unfortunately, the embryonic lethality of biallelic excision of PTEN has inhibited the study of complete PTEN deletion in the development and progression of cancer. By crossing PTEN conditional knockout mice with transgenic mice expressing a tamoxifen-inducible Cre-ER(T) under the control of a chicken actin promoter, we have generated a tamoxifen-inducible mouse model that allows temporal control of PTEN deletion. Interestingly, administration of a single dose of tamoxifen resulted in PTEN deletion mainly in epithelial cells, but not in stromal, mesenchymal or hematopoietic cells. Using the mT/mG double-fluorescent Cre reporter mice, we demonstrate that epithelial-specific PTEN excision was caused by differential Cre activity among tissues and cells types. Tamoxifen-induced deletion of PTEN resulted in extremely rapid and consistent formation of endometrial in situ adenocarcinoma, prostate intraepithelial neoplasia and thyroid hyperplasia. We also analyzed the role of PTEN ablation in other epithelial cells, such as the tubular cells of the kidney, hepatocytes, colonic epithelial cells or bronchiolar epithelium, but those tissues did not exhibit neoplastic growth. Finally, to validate this model as a tool to assay the efficacy of anti-tumor drugs in PTEN deficiency, we administered the mTOR inhibitor everolimus to mice with induced PTEN deletion. Everolimus dramatically reduced the progression of endometrial proliferations and significantly reduced thyroid hyperplasia. This model could be a valuable tool to study the cell-autonomous mechanisms involved in PTEN-loss-induced carcinogenesis and provides a good platform to study the effect of anti-neoplastic drugs on PTEN-negative tumors.

Blockade of NFκB activity by Sunitinib increases cell death in Bortezomib-treated endometrial carcinoma cells.

Endometrial carcinoma is one of the most common malignancies in the female genital tract, usually treated by surgery and radiotherapy. Chemotherapy is used when endometrial carcinoma is associated with widespread metastasis or when the tumor recurs after radiation therapy. In the present study, we demonstrate that the tyrosine kinase receptor inhibitor Sunitinib reduces cell viability, proliferation, clonogenicity and induces apoptotic cell death in endometrial carcinoma cell lines, which is not due to its action through the most known targets like VEGFR, nor through EGFR as demonstrated in this work. Interestingly, Sunitinib reduces NFκB transcriptional activity either at basal level or activation by EGF or TNF-α. We observed that Sunitinib was able to inhibit the Bortezomib-induced NFκB transcriptional activity which correlates with a decrease of the phosphorylated levels of IKKα and ß, p65 and IκBα. We evaluated the nature of the interaction between Sunitinib and Bortezomib by the dose effect method and identified a synergistic effect (combination index < 1). Analogously, silencing of p65 expression by lentiviral-mediated short-hairpin RNA delivery in Bortezomib treated cells leads to a strongly increased sensitivity to Bortezomib apoptotic cell death. Altogether our results suggest that the combination of Sunitinib and Bortezomib could be considered a promising treatment for endometrial carcinoma after failure of surgery and radiation.

Immunohistochemical features of post-radiation vaginal recurrences of endometrioid carcinomas of the endometrium: role for proteins involved in resistance to apoptosis and hypoxia.

AIMS: Endometrioid carcinoma of the endometrium (EEC) is treated with surgery and radiotherapy. Post-radiation recurrences are associated with increased risk of metastases. Comparison of the expression of genes important in the development and progression of EEC, and others involved in resistance to apoptosis and hypoxia and adaptation to radiation, was performed between post-radiation vaginal recurrences (PVRs) and primary EECs. We tried to reproduce the results by exposing an EEC cell line to hypoxia and radiation. METHODS AND RESULTS: Immunohistochemistry and tissue microarrays were used to compare 24 PVRs with 82 primary EECs. PVRs exhibited increased expression of p53 (P < 0.0001), cytoplasmic FLICE-inhibitory protein (FLIP) (P < 0.0001), and Ki67 (P < 0.0001), and nuclear staining for FLIP, nuclear factor kappaB (NF-κB) family members (p50, P < 0.0001; c-Rel, P = 0.0077; RelB, P = 0.0157), and ß-catenin (P = 0.0001). Differences regarding p50, hypoxia-inducible factor 1α (HIF-1α), and cytoplasmic FLIP were statistically significant when PVRs and primary EECs were matched for histological grade. Exposure of the EEC cell line to hypoxia induced nuclear expression of ß-catenin, FLIP, and HIF-1α, as well as increased NF-κB activity. No changes in FLIP, HIF-1α or NF-κB were seen when cells were exposed to radiation. Nuclear expression of ß-catenin was seen at 3 Gy, but not at 1 Gy. CONCLUSIONS: Genes involved in resistance to hypoxia are expressed in PVRs, and may play a role in the development of post-radiation recurrences.

KSR1 is overexpressed in endometrial carcinoma and regulates proliferation and TRAIL-induced apoptosis by modulating FLIP levels.

The Raf/MEK/extracellular signal-regulated kinase (ERK) pathway participates in many processes altered in development and progression of cancer in human beings such as proliferation, transformation, differentiation, and apoptosis. Kinase suppressor of Ras 1 (KSR1) can interact with various kinases of the Raf/MEK/extracellular signal-regulated kinase pathway to enhance its activation. The role of KSR1 in endometrial carcinogenesis was investigated. cDNA and tissue microarrays demonstrated that expression of KSR1 was up-regulated in endometrial carcinoma. Furthermore, inhibition of KSR1 expression by specific small hairpin RNA resulted in reduction of both proliferation and anchorage-independent cell growth properties of endometrial cancer cells. Because inhibition of apoptosis has a pivotal role in endometrial carcinogenesis, the effects of KSR1 in regulation of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis were investigated. KSR1 knock-down sensitized resistant endometrial cell lines to both TRAIL- and Fas-induced apoptosis. Sensitization to TRAIL and agonistic anti-Fas antibody was caused by down-regulation of FLIP (FLICE-inhibitory protein). Also investigated was the molecular mechanism by which KSR1 regulates FLIP protein levels. It was demonstrated that KSR1 small hairpin RNA did not affect FLIP transcription or degradation. Rather, FLIP down-regulation was caused by Fas-associated death domain protein-dependent inhibition of FLIP translation triggered after TRAIL stimulation in KSR1-silenced cells. Re-expression of heterologous KSR1 in cells with down-regulated endogenous KSR1 restored FLIP protein levels and TRAIL resistance. In conclusion, KSR1 regulates endometrial sensitivity to TRAIL by regulating FLIP levels.