In vitro characterization of a small molecule PD-1 inhibitor that targets the PD-l/PD-L1 interaction.

Targeting the programmed cell death protein 1/programmed cell death ligand 1 (PD-1/PD-L1) axis with monoclonal antibodies (mAbs) represents a crucial breakthrough in anticancer therapy, but mAbs are limited by their poor oral bioavailability, adverse events in multiple organ systems, and primary, adaptive, and acquired resistance, amongst other issues. More recently, the advent of small molecule inhibitors that target the PD-1/PD-L1 axis have shown promising cellular inhibitory activity and the potential to counteract the disadvantages of mAbs. In this study, structure-based virtual screening identified small molecule inhibitors that effectively inhibited the PD-1/PD-L1 interaction. Six of those small molecule inhibitors were applied to cell-based experiments targeting PD-1: CH-1, CH-2, CH-3, CH-4, CH-5, and CH-6. Of all 6, CH-4 displayed the lowest cytotoxicity and strongest inhibitory activity towards the PD-1/PD-L1 interaction. The experiments revealed that CH-4 inhibited the interaction of soluble form PD-L1 (sPD-L1) with PD-1 surface protein expressed by KG-1 cells. Investigations into CH-4 analogs revealed that CH-4.7 effectively blocked the PD-1/sPD-L1 interaction, but sustained the secretion of interleukin-2 and interferon-γ by Jurkat cells. Our experiments revealed a novel small molecule inhibitor that blocks the interaction of PD-1/sPD-L1 and potentially offers an alternative PD-1 target for immune checkpoint therapy.

Non-stem bladder cancer cell-derived extracellular vesicles promote cancer stem cell survival in response to chemotherapy.

BACKGROUND: Chemosenstive non-stem cancer cells (NSCCs) constitute the bulk of tumors and are considered as part of the cancer stem cell (CSC) niche in the tumor microenvironment (TME). Tumor-derived extracellular vesicles (EVs) mediate the communication between tumors and the TME. In this study, we sought to investigate the impacts of EVs released by NSCCs on the maintenance of CSC properties and chemoresistance. METHODS: We employed murine MB49 bladder cancer (BC) sub-lines representing CSCs and NSCCs as a model system. Chemotherapy drugs were used to treat NSCCs in order to collect conditioned EVs. The impacts of NSCC-derived EVs on CSC progression were evaluated through sphere formation, cytotoxicity, migration, and invasion assays, and by analyzing surface marker expression on these BC cells. Differential proteomic analyses were conducted to identify cargo protein candidates involved in the EV-mediated communication between NSCCs and CSCs. RESULTS: NSCC-derived EVs contained cargo proteins enriched in proteostasis-related functions, and significantly altered the development of CSCs such that they were more intrinsically chemoresistant, aggressive, and better able to undergo self-renewal. CONCLUSIONS: We thus identified a novel communication mechanism whereby NSCC-EVs can alter the relative fitness of CSCs to promote disease progression and the acquisition of chemoresistance.

Androgen/Androgen Receptor Signaling in Ovarian Cancer: Molecular Regulation and Therapeutic Potentials.

Ovarian cancer (OVCA) arises from three cellular origins, namely surface epithelial cells, germ cells, and stromal cells. More than 85% of OVCAs are EOCs (epithelial ovarian carcinomas), which are the most lethal gynecological malignancies. Cancer stem/progenitor cells (CSPCs) are considered to be cancer promoters due to their capacity for unlimited self-renewal and drug resistance. Androgen receptor (AR) belongs to the nuclear receptor superfamily and can be activated through binding to its ligand androgens. Studies have reported an association between AR expression and EOC carcinogenesis, and AR is suggested to be involved in proliferation, migration/invasion, and stemness. In addition, alternative AR activating signals, including both ligand-dependent and ligand-independent, are involved in OVCA progression. Although some clinical trials have previously been conducted to evaluate the effects of anti-androgens in EOC, no significant results have been reported. In contrast, experimental studies evaluating the effects of anti-androgen or anti-AR reagents in AR-expressing EOC models have demonstrated positive results for suppressing disease progression. Since AR is involved in complex signaling pathways and may be expressed at various levels in OVCA, the aim of this article was to provide an overview of current studies and perspectives regarding the relevance of androgen/AR roles in OVCA.

Androgen Receptor Enhances the Efficacy of Sorafenib Against Hepatocellular Carcinoma Through Enriched EpCAM Stemness.

BACKGROUND/AIM: The role of androgen receptor (AR) in hepatocellular carcinoma (HCC) development is controversial. Therefore, the translational value of targeting AR in HCC is unknown. Sorafenib, a multiple kinase inhibitor, is the standard therapy for patients with unresectable HCC. This study investigated sorafenib effect on AR in experimental models of HCC. MATERIAL AND METHODS: AR cDNA was introduced into HCC cells and in vitro cell growth and in vivo tumor growth were measured. Sphere cells, as well as epithelial cell adhesion molecule-positive (EpCAM+) and CD133+ cells were isolated from HCC cells with/without AR expression to observe in vitro/in vivo effects. Liver specific AR knockout in mouse models of spontaneous HCC (carcinogen-induced and hepatitis B virus-related HCC) was also implemented to examine gene expression. HCC cells/tumors were treated with sorafenib in order to determine effects on tumor growth and related gene expression. RESULT: AR cDNA increased transactivation function, increased colony/sphere-forming activities, and enhanced tumorigenicity in HCC cells compared to their parental cells. Expression of the stemness marker EpCAM was also dramatically increased. In carcinogen-and HBV-induced HCC models, EpCAM+ cells were significantly reduced in AR-knockout mice compared to wild-type HCCs. In addition, AR reduced sorafenib-related signals, e.g. extracellular-regulated kinase, AKT serine/threonine kinase 1, and p38 mitogen-activated protein kinase, compared to that in parental cells. Regarding sorafenib cytotoxicity, AR-expressing cells were vulnerable to treatment. Moreover, the half maximal-inhibitory concentration (IC50) was drastically lowered in AR+/EpCAM+ compared to AR-/EpCAM- sphere cells. Strikingly, the IC50 in AR+/CD133+ vs. AR-/CD133+ cells were similar. Moreover, sorafenib robustly suppressed tumor growth in implanted AR+/EpCAM+ cells but not AR-/EpCAM- ones. Finally, bioinformatics analyses revealed EpCAM to be a prognostic biomarker in Asian and non-alcohol-consuming patients with HCC, suggesting suitability of a sorafenib regimen for such patients. CONCLUSION: AR+/EpCAM+ may be a marker of responsiveness to sorafenib for patients with HCC. Prospective surveys associating AR/EpCAM expression with therapy outcomes are essential.

LDLR-mediated lipidome-transcriptome reprogramming in cisplatin insensitivity.

Platinum-based therapy remains the cornerstone for cancer therapy; however, its efficacy varies. The role of lipoprotein receptor-mediated lipid entry for cancer development has been reported. Yet, the roles and mechanism of the low-density lipoprotein receptor (LDLR) in chemo-sensitivities are unknown. In the current report, we used epithelial ovarian cancer (EOC), composed of various cellularities, to study this issue. Using public cDNA microarray database and single cohort study, LDLR expressions were positively associated with epithelial ovarian carcinomas (EOCs) platinum-based chemotherapy patients' disease prognosis. In vitro and in vivo add-in/silencing LDLR was introduced to determine cisplatin sensitivity and cancer growth. Results revealed that knocked-down LDLR could sensitize while overexpressed LDLR could insensitize EOC cells to the cytotoxic effects of cisplatin. Moreover, the trans-omics approaches depicted an LDLR→LPC (Lyso-phosphatidylcholine)→FAM83B (phospholipase-related)→FGFRs (cisplatin sensitivity and phospholipase-related) regulatory axis. Finally, the manipulation of LDLR expression in EOC cells was found to determine the efficacy of cisplatin therapy in terms of tumor suppression. In conclusion, the LDLR→LPC→FAM83B→FGFRs axis is an example of tumor macroenvironmental regulation of therapy outcomes. Relatedly, LDLR expression could serve as a biomarker of chemotherapy sensitivity in EOCs. Significance: this study describes the role of LDLR in the development of insensitivity to platinum-based chemotherapy in epithelial ovarian cancer. The lipidome (e.g., LPC) and transcriptome (e.g., FAM38B) interactions revealed using trans-omics approaches an LDLR→LPC→FAM83B→FGFRs regulatory axis in cancer cells, in an animal model, and in patients.

Preclinical evaluation of exemestane as a novel chemotherapy for gastric cancer.

CYP19A1/aromatase (Ar) is a prognostic biomarker of gastric cancer (GCa). Ar is a critical enzyme for converting androstenedione to oestradiol in the steroidogenesis cascade. For decades, Ar has been targeted with Ar inhibitors (ARIs) in gynaecologic malignancies; however, it is unexplored in GCa. A single-cohort tissue microarray examination was conducted to study the association between Ar expression and disease outcome in Asian patients with GCa. The results revealed that Ar was a prognostic promoter. Bioinformatics analyses conducted on a Caucasian-based cDNA microarray databank showed Ar to be positively associated with GCa prognosis for multiple clinical modalities, including surgery, 5-Fluorouracil (5-FU) for adjuvant chemotherapy, or HER2 positivity. These findings imply that targeting Ar expression exhibits a potential for fulfilling unmet medical needs. Hence, Ar-targeting compounds were tested, and the results showed that exemestane exhibited superior cancer-suppressing efficacy to other ARIs. In addition, exemestane down-regulated Ar expression. Ablating Ar abundance with short hairpin (sh)Ar could also suppress GCa cell growth, and adding 5-FU could facilitate this effect. Notably, adding oestradiol could not prevent exemestane or shAr effects, implicating a nonenzymatic mechanism of Ar in cancer growth. Regarding translational research, treatment with exemestane alone exhibited tumour suppression efficacy in a dose-dependent manner. Combining subminimal doses of 5-FU and exemestane exerted an excellent tumour suppression effect without influencing bodyweight. This study validated the therapeutic potentials of exemestane in GCa. Combination of metronomic 5-FU and exemestane for GCa therapy is recommended.

Increase Paclitaxel Sensitivity to Better Suppress Serous Epithelial Ovarian Cancer via Ablating Androgen Receptor/Aryl Hydrocarbon Receptor-ABCG2 Axis.

BACKGROUND: Epithelial ovarian cancer (EOC) is one of the most lethal gynecological malignancies and presents chemoresistance after chemotherapy treatment. Androgen receptor (AR) has been known to participate in proliferation. Yet the mechanisms of the resistance of this drug and its linkage to the AR remains unclear. METHODS: To elucidate AR-related paclitaxel sensitivity, co-IP, luciferase reporter assay and ChIP assay were performed to identify that AR direct-regulated ABCG2 expression under paclitaxel treatment. IHC staining by AR antibody presented higher AR expression in serous-type patients than other types. AR degradation enhancer (ASC-J9) was used to examine paclitaxel-associated and paclitaxel-resistant cytotoxicity in vitro and in vivo. RESULTS: We found AR/aryl hydrocarbon receptor (AhR)-mediates ABCG2 expression and leads to a change in paclitaxel cytotoxicity/sensitivity in EOC serous subtype cell lines. Molecular mechanism study showed that paclitaxel activated AR transactivity and bound to alternative ARE in the ABCG2 proximal promoter region. To identify AR as a potential therapeutic target, the ASC-J9 was used to re-sensitize paclitaxel-resistant EOC tumors upon paclitaxel treatment in vitro and in vivo. CONCLUSION: The results demonstrated that activation of AR transactivity beyond the androgen-associated biological effect. This novel AR mechanism explains that degradation of AR is the most effective therapeutic strategy for treating AR-positive EOC serous subtype.

Ligand-independent androgen receptors promote ovarian teratocarcinoma cell growth by stimulating self-renewal of cancer stem/progenitor cells.

BACKGROUND: Ovarian teratocarcinoma (OVTC) arises from germ cells and contains a high percentage of cancer stem/progenitor cells (CSPCs), which promote cancer development through their ability to self-renew. Androgen and androgen receptor (androgen/AR) signaling has been reported to participate in cancer stemness in some types of cancer; however, this phenomenon has never been studied in OVTC. METHODS: Ovarian teratocarcinoma cell line PA1 was manipulated to overexpress or knockdown AR by lentiviral deliver system. After analyzing of AR expression in PA1 cells, cell growth assay was assessed at every given time point. In order to determine ligand effect on AR actions, luciferase assay was performed to evaluate endogenous and exogenous AR function in PA1 cells. CD133 stem cell marker antibody was used to identify CSPCs in PA1 cells, and AR expression level in enriched CSPCs was determined. To assess AR effects on CD133+ population progression, stem cell functional assays (side population, sphere formation assay, CD133 expression) were used to analyze role of AR in PA1 CSPCs. In tissue specimen, immunohistochemistry staining was used to carry out AR and CD133 staining in normal and tumor tissue. RESULTS: We examined androgen/AR signaling in OVTC PA1 cells, a CSPCs-rich cell line, and found that AR, but not androgen, promoted cell growth. We also examined the effects of AR on CSPCs characteristics and found that AR expression was more abundant in CD133+ cells, a well-defined ovarian cancer stem/progenitor marker, than in CD133- populations. Moreover, results of the sphere formation assay revealed that AR expression was required to maintain CSPCs populations. Interestingly, this AR-governed self-renewal capacity of CSPCs was only observed in CD133+ cells. In addition, we found that AR-mediated CSPCs enrichment was accompanied by down-regulation of p53 and p16. Finally, co-expression of AR and CD133 was more abundant in OVTC lesions than in normal ovarian tissue. CONCLUSION: The results of this study suggest that AR itself might play a ligand-independent role in the development of OVTC.

Androgen receptor increases CD133 expression and progenitor-like population that associate with cisplatin resistance in endometrial cancer cell line.

Endometrial cancer (EMC) is a sex steroid hormone-related female malignancy. Androgen and androgen receptor (androgen/AR) signals have been implicated in EMC progression. Cancer stem/progenitor cells (CSPCs) are suspected to link to chemoresistance in patients with EMC. In this study, we examined the androgen/AR roles in cisplatin resistance and CSPC population. We found AR expression increased naive EMC side population, CSPC population, cell migration, and epithelial-mesenchymal transition. Meanwhile, it decreased cisplatin cytotoxic effect on EMC cells. Collaterally, endogenous AR expressions in EMC cells were upregulated in the cisplatin-resisting state. Moreover, AR expression could further enhance CD133 expression, CSPC-related markers, and drug-resistance gene messenger RNA expression in EMC cells. Finally, the AR-associated gene expression might go through indirect regulation. This is the first report revealing AR function on EMC cells' CSPC and cisplatin resistance.

Non-genomic estrogen/estrogen receptor α promotes cellular malignancy of immature ovarian teratoma in vitro.

Malignant immature ovarian teratomas (IOTs) most often occur in women of reproductive age. It is unclear, however, what roles estrogenic signaling plays in the development of IOT. In this study, we examined whether estrogen receptors (ERα and ß) promote the cellular malignancy of IOT. Estradiol (E2), PPT (propylpyrazole), and DPN (diarylpropionitrile) (ERα- and ß-specific agonists, respectively), as well as ERα- or ERß-specific short hairpin (sh)RNA were applied to PA-1 cells, a well-characterized IOT cell line. Cellular tumorigenic characteristics, for example, cell migration/invasion, expression of the cancer stem/progenitor cell marker CD133, and evidence for epithelial-mesenchymal transition (EMT) were examined. In PA-1 cells that expressed ERα and ERß, we found that ERα promoted cell migration and invasion. We also found that E2/ERα signaling altered cell behavior through non-classical transactivation function. Our data show non-genomic E2/ERα activations of focal adhesion kinase-Ras homolog gene family member A (FAK-RhoA) and ERK governed cell mobility capacity. Moreover, E2/ERα signaling induces EMT and overexpression of CD133 through upregulation micro-RNA 21 (miR21; IOT stem/progenitor promoter), and ERK phosphorylations. Furthermore, E2/ERα signaling triggers a positive feedback regulatory loop within miR21 and ERK. At last, expression levels of ERα, CD133, and EMT markers in IOT tissue samples were examined by immunohistochemistry. We found that cytosolic ERα was co-expressed with CD133 and mesenchymal cell markers but not epithelial cell markers. In conclusion, estrogenic signals exert malignant transformation capacity of cancer cells, exclusively through non-genomic regulation in female germ cell tumors.

MicroRNA-21 promotes the ovarian teratocarcinoma PA1 cell line by sustaining cancer stem/progenitor populations in vitro.

INTRODUCTION: Resistance of cancer stem/progenitor cells (CSPCs) to chemotherapy can lead to cancer relapse. Ovarian teratocarcinoma (OVTC) arises from germ cells and comprises pluripotent cells that can be used to study cancer cell stemness. In this study, we evaluated whether microRNA-21 (miR-21) promotes ovarian teratocarcinoma by maintaining cancer stem/progenitor populations. METHODS: The lentiviral delivery system was used to upregulate or to suppress the expression of miR-21 in the human ovarian teratocarcinoma cell line PA1 and cell growth assays were used to monitor the expression of miR-21 at different time points. Antibodies directed toward CD133, a stem cell marker, were used to identify CSPCs in the PA1 cell population, and the level of miR-21 expression was determined in enriched CSPCs. Stem cell functional assays (sphere assay and assays for CD133 expression) were used to assess the effects of miR-21 on progression of the CD133+ population. RESULTS: Knockdown of miR-21 in PA1 cells attenuated growth of PA1 cells whereas overexpression of miR-21 promoted cell growth. Moreover, knockdown of miR-21 resulted in a marked reduction in the CD133+ population and sphere formation of CSPCs. In contrast, overexpression of miR-21 resulted in a marked increase in the population of CD133+ cells as well as sphere formation of CSPCs. CONCLUSIONS: MicroRNA-21 plays a significant role in cancer growth by regulating stemness in cancer cells.