Identification and Characterization of a Small Molecule Bcl-2 Functional Converter.

Cancer cells exploit the expression of anti-apoptotic protein Bcl-2 to evade apoptosis and develop resistance to therapeutics. High levels of Bcl-2 leads to sequestration of pro-apoptotic proteins causing the apoptotic machinery to halt. In this study, we report discovery of a small molecule, BFC1108 (5-chloro-N-(2-ethoxyphenyl)-2-[(4-methoxybenzyol)amino]benzamide), which targets Bcl-2 and converts it into a pro-apoptotic protein. The apoptotic effect of BFC1108 is not inhibited, but rather potentiated, by Bcl-2 overexpression. BFC1108 induces a conformational change in Bcl-2, resulting in the exposure of its BH3 domain both in vitro and in vivo. BFC1108 suppresses the growth of triple-negative breast cancer xenografts with high Bcl-2 expression and inhibits breast cancer lung metastasis. This study demonstrates a novel approach to targeting Bcl-2 using BFC1108, a small molecule Bcl-2 functional converter that effectively induces apoptosis in Bcl-2-expressing cancers. SIGNIFICANCE: We report the identification of a small molecule that exposes the Bcl-2 killer conformation and induces death in Bcl-2-expressing cancer cells. Selective targeting of Bcl-2 and elimination of cancer cells expressing Bcl-2 opens up new therapeutic avenues.

Irreducible posterior hip dislocation in the setting of a multifocal displaced pelvic ring injury: A case report.

Case report: Traumatic hip dislocations require prompt diagnosis and reduction to preserve the native joint. The classic irreducible posterior hip fracture-dislocation has been described as an immobile, slightly flexed, and internally rotated hip on physical exam. Classically, this irreducible pattern is associated with an ipsilateral femoral head fracture. The purpose of our report is to present an irreducible posterior hip dislocation with preserved motion in the setting of an unstable pelvic ring injury without associated femoral head pathology. Despite lacking clinical features of an irreducible hip, closed reduction in the emergency and operating rooms was unsuccessful, even after frame application for pelvis stability. Persistent irreducibility necessitated open reduction, where the femoral head was found to be buttonholed through the posterior hip capsule and blocking reduction. Conclusion: A posteriorly dislocated hip with preserved motion in the setting of a concomitant unstable pelvic ring injury may belie the true locked nature of the femoroacetabular dislocation and high suspicion for femoral head incarceration is required. The description of this unique irreducible fracture pattern and the stepwise approach used for reduction may be useful for other surgeons who may encounter similar patterns of injury.

Socioeconomic and insurance-related disparities in disease-specific survival among patients with metastatic bone disease.

BACKGROUND: Approximately 5% of cancer patients in the United States presented with metastatic bone disease (MBD) at diagnosis. Current study explores the disparities in survival for patients with MBD. METHODS: Patients with the diagnosis of MBD at presentation for the five most common primary anatomical sites were extracted from Surveillance, Epidemiology, and End Results Census tract-level dataset (2010-2016). Kaplan-Meier and Cox Proportional Hazard models were used to evaluate survival, and prognostic factors for each cohort. Prognostic significance of socioeconomic status (SES) and insurance status were ascertained. RESULTS: The five most common anatomical-sites with MBD at presentation included "lung" (n = 59 739), "prostate" (n = 19 732), "breast" (n = 16 244), "renal and urothelium" (n = 7718) and "colon" (n= 3068). Lower SES was an independent risk factor for worse disease-specific survival (DSS) for patients with MBD originating from lung, prostate, breast and colon. Lack of insurance was an independent risk factor for worse DSS for MBD patients with primary tumors in lung and breast. CONCLUSIONS: MBD patients from the five most common primary sites demonstrated SES and insurance-related disparities in disease-specific survival. This is the first and largest study to explore SES and insurance-related disparities among patients specifically afflicted with MBD. Our findings highlight vulnerability of patients with MBD across multiple primary sites to financial toxicity.

Head and Neck Cutaneous Soft-Tissue Sarcoma Demonstrate Sex and Racial/Ethnic Disparities in Incidence and Socioeconomic Disparities in Survival.

BACKGROUND: Cutaneous soft-tissue sarcoma (CSTS) of the head and neck are rare and are known to have aggressive clinical course. The current study utilizes a population-based registry in the U.S. to characterize these malignancies and explore disparities. METHODS: National Cancer Institute's (NCI) Surveillance, Epidemiology and End Result (SEER) database from 2000 to 2018 was queried to report incidence and survival data in 4253 cases in the U.S. RESULTS: Males were 5.37 times more likely and Non-Hispanic-White people (NHW) were 4.62 times more likely than females and Non-Hispanic-Black people (NHB) to develop CSTS of the head and neck. The overall incidence was 0.27 per 100,000 persons in 2018, with a significant increase since 2000. Advanced age and stage, histologic group other than 'fibromatous sarcoma' and lower SES groups were independent factors for worse overall survival. CONCLUSIONS: CSTS of the head and neck demonstrate sex and racial/ethnic disparities in incidence and socioeconomic disparities in overall survival. LEVEL OF EVIDENCE: II.

Impact of local treatment modality on overall- and disease-specific survival for nonmetastatic pelvic and sacral Ewing sarcoma.

PURPOSE: The ideal local treatment modality for pelvic and sacral Ewing sarcoma (EWS) is controversial. METHODS: We present the data from the American College of Surgeon's National Cancer Database (NCDB) and the National Cancer Institute's Surveillance, Epidemiology and End Result (SEER) database to investigate the impact of local treatment modalities on survival for nonmetastatic pelvic and sacral Ewing sarcoma. Local treatment includes "surgery," "radiation," and a combination of "surgery and radiation." RESULTS: A total of 235 cases from SEER and 285 cases from NCDB were analyzed. Patients with "localized" stage (intraosseous) in the SEER database did not show any statistically significant difference in the disease-specific survival (DSS) for any of the local treatment modalities. Similar findings were observed for overall survival among patients with American Joint Committee on Cancer (AJCC) stage II and III in the NCDB database. However, patients with nonmetastatic disease, particularly regional disease (extraosseous), showed improved DSS with surgery only, in the SEER. CONCLUSION: We found similar levels of efficacy for different treatment modalities for patients with intraosseous and AJCC II and III pelvic and sacral EWS. "Radiotherapy" is the most common local treatment modality employed in the United States. A prospective, randomized controlled trial with a direct head-to-head comparison is needed for a definitive conclusion.

Sex, racial/ethnic and socioeconomic disparities in patients with metastatic bone disease.

BACKGROUND: We have analyzed sex, race/ethnicity or socioeconomic disparities in the incidence of metastatic bone disease (MBD). METHODS: Patients with the diagnosis of MBD at presentation for five most common primary anatomical sites was extracted from Surveillance, Epidemiology, and End Results Census tract-level dataset. Mean incidence of MBD for different sex, racial/ethnic and socioeconomic groups were compared. RESULTS: The five most common anatomical sites with MBD at presentation include "lung: (n = 59 739), "prostate" (n = 19 732), "breast" (n = 16 244), "renal" (n = 7718) and "colon" (n = 3068). There was an increase in incidence of MBD among cancers originating from prostate (annual percentage change [APC] 4.94), renal (APC 2.55), and colon (APC 3.21) (p < 0.05 for all). Non-Hispanic Blacks had higher incidence of MBD for prostate and breast primary sites (p < 0.001). Non-Hispanic American Indian Alaskan Native had higher incidence of MBD for cancers originating from renal (p < 0.001) and colon (p = 0.049). A higher incidence of MBD was seen in lower socioeconomic status (SES) groups for the selected sites (p < 0.001). CONCLUSIONS: These findings suggest that there are multiple sex-related, racial/ethnic and SES disparities in the incidence of MBD from the 5 most common primary sites. Higher incidence seen among lower SES suggests delay in diagnosis and limited access to screening modalities.

Analysis of tumor-infiltrating NK and T cells highlights IL-15 stimulation and TIGIT blockade as a combination immunotherapy strategy for soft tissue sarcomas.

PURPOSE: Given the unmet need for novel immunotherapy in soft tissue sarcoma (STS), we sought to characterize the phenotype and function of intratumoral natural killer (NK) and T cells to identify novel strategies to augment tumor-infiltrating lymphocyte (TIL) function. EXPERIMENTAL DESIGN: Using prospectively collected specimens from dogs and humans with sarcomas, archived specimens, and The Cancer Genome Atlas (TCGA) data, we evaluated blood and tumor NK and T cell phenotype and function and correlated those with outcome. We then assessed the effects of interleukin 15 (IL-15) stimulation on both NK and T cell activation and TIGIT upregulation. Finally, we evaluated cytotoxic effects of IL-15 combined with TIGIT blockade using a novel anti-TIGIT antibody. RESULTS: TILs were strongly associated with survival outcome in both archived tissue and TCGA, but higher TIL content was also associated with higher TIGIT expression. Compared with blood, intratumoral NK and T cells showed significantly higher expression of both activation and exhaustion markers, in particular TIGIT. Ex vivo stimulation of blood and tumor NK and T cells from patients with STS with IL-15 further increased both activation and exhaustion markers, including TIGIT. Dogs with metastatic osteosarcoma receiving inhaled IL-15 also exhibited upregulation of activation markers and TIGIT. Ex vivo, combined IL-15 and TIGIT blockade using STS blood and tumor specimens significantly increased cytotoxicity against STS targets. CONCLUSION: Intratumoral NK and T cells are prognostic in STS, but their activation is marked by significant upregulation of TIGIT. Our data suggest that combined IL-15 and TIGIT blockade may be a promising clinical strategy in STS.

Down-regulation of Skp2 expression inhibits invasion and lung metastasis in osteosarcoma.

Osteosarcoma (OS), the most common primary cancer of bone, exhibits a high propensity for local invasion and distant metastasis. This study sought to elucidate the role of S phase kinase-associated protein (Skp2) in osteosarcoma invasion and metastasis and to explore flavokawain A (FKA), a natural chalcone from kava extract, as a potential Skp2 targeting agent for preventing osteosarcoma progression. Skp2 was found to be overexpressed in multiple osteosarcoma cell lines, including 5 standard and 8 primary patient-derived cell lines. Patients whose tumors expressed high levels of Skp2 sustained a significantly worse metastasis-free (p = 0.0095) and overall survival (p = 0.0013) than those with low Skp2. Skp2 knockdown markedly reduced in vitro cellular invasion and in vivo lung metastasis in an orthotopic mouse model of osteosarcoma. Similar to Skp2 knockdown, treatment with FKA also reduced Skp2 expression in osteosarcoma cell lines and blocked the invasion of osteosarcoma cells in vitro and lung metastasis in vivo. Together, our findings suggest that Skp2 is a promising therapeutic target in osteosarcoma, and that FKA may be an effective Skp2-targeted therapy to reduce osteosarcoma metastasis.

Induction of apoptosis and suppression of tumor growth by Nur77-derived Bcl-2 converting peptide in chemoresistant lung cancer cells.

Resistance to chemotherapy is a major cause of treatment failure and poor overall survival in patients with lung cancer. Identification of molecular targets present in resistant cancer cells is essential for addressing therapeutic resistance and prolonging lung cancer patient survival. Members of the B-cell lymphoma 2 (Bcl-2) family of proteins are associated with chemotherapeutic resistance. In this study, we found that pro-survival protein Bcl-2 is upregulated in paclitaxel resistant cells, potentially contributing to chemotherapy resistance. To exploit the increase in Bcl-2 expression for targeting therapy resistance, we investigated the effects of a peptide derived from the nuclear receptor Nur77 that converts Bcl-2 from an anti-apoptotic protein to a pro-apoptotic protein. The Nur77 derived peptide preferentially induced apoptosis in paclitaxel-resistant cancer cells with high expression of Bcl-2. This peptide also induced apoptosis of multidrug resistant H69AR lung cancer cells that express Bcl-2 and inhibited their growth in 3D spheroids. The Nur77 peptide strongly suppressed the growth of paclitaxel-resistant lung cancer cells in a zebrafish xenograft tumor model. Taken together, our data supports a new strategy for treating lung cancers that acquire resistance to chemotherapy through overexpression of Bcl-2.

Identification of a Raloxifene Analog That Promotes AhR-Mediated Apoptosis in Cancer Cells.

We previously reported that raloxifene, an estrogen receptor modulator, is also a ligand for the aryl hydrocarbon receptor (AhR). Raloxifene induces apoptosis in estrogen receptor-negative human cancer cells through the AhR. We performed structure-activity studies with seven raloxifene analogs to better understand the structural requirements of raloxifene for induction of AhR-mediated transcriptional activity and apoptosis. We identified Y134 as a raloxifene analog that activates AhR-mediated transcriptional activity and induces apoptosis in MDA-MB-231 human triple negative breast cancer cells. Suppression of AhR expression strongly reduced apoptosis induced by Y134, indicating the requirement of AhR for Y134-induced apoptosis. Y134 also induced apoptosis in hepatoma cells without having an effect on cell cycle regulation. Toxicity testing on zebrafish embryos revealed that Y134 has a significantly better safety profile than raloxifene. Our studies also identified an analog of raloxifene that acts as a partial antagonist of the AhR, and is capable of inhibiting AhR agonist-induced transcriptional activity. We conclude that Y134 is a promising raloxifene analog for further optimization as an anti-cancer agent targeting the AhR.

The aryl hydrocarbon receptor is required for induction of p21cip1/waf1 expression and growth inhibition by SU5416 in hepatoma cells.

The aryl hydrocarbon receptor (AhR) is a potential clinical target for cancer and autoimmune dysfunction. Identifying selective AhR modulators that produce desirable clinical outcomes represents an opportunity for developing new anti-cancer agents. Repurposing clinically-used drugs with established safety profiles that activate the AhR represents a good starting place to pursue this goal. In this study, we characterized the AhR-dependent effects of SU5416 (Semaxanib) following its identification in a small-molecule library screen. SU5416 potently activated AhR-dependent reporter genes, induced AhR nuclear localization, facilitated AhR-DNA binding, and increased, expression of its endogenous target genes. SU5416 significantly inhibited proliferation of Hepa1 hepatoma cells in an AhR-dependent manner, but did not induce apoptosis. SU5416 also inhibited the growth of human HepG2 liver cancer cells. The effects of SU5416 correlated with an increased G1 population and increased expression of cell cycle inhibitor p21cip1/waf1 at both the mRNA and protein level. Increased expression of p21cip1/waf1 by SU5416 required expression of both AhR and Arnt. In addition, evidence for long-term activation of the AhR in vivo by a single dose of SU5416 was identified by analyzing published microarray data. Our results provide support for continued investigation of the AhR as therapeutic for cancers such as hepatocellular carcinoma. In addition, our findings raise the possibility that some of the previously observed anti-proliferative effects of SU5416 may be due to activation of the AhR.

The aryl hydrocarbon receptor mediates leflunomide-induced growth inhibition of melanoma cells.

A novel role of the dihydroorotatedehydrogenase (DHODH) inhibitor leflunomide as a potential anti-melanoma therapy was recently reported (Nature 471:518-22, 2011). We previously reported that leflunomide strongly activates the transcriptional activity of the Aryl Hydrocarbon Receptor (AhR). We therefore tested whether the AhR regulates the anti-proliferative effects of leflunomide in melanoma. We first evaluated the expression of AhR in melanoma cells and found that AhR is highly expressed in A375 melanoma as well as in several other cancer cell types. To evaluate whether AhR plays a role in regulating the growth inhibitory effects of leflunomide in A375 cells, we generated a stable cell line from parental A375 cells expressing a doxycycline (DOX) inducible AhR shRNA. Using these cells in the absence or presence of DOX (normal AhR levels or AhR-knockdown, respectively) we found that the anti-proliferative effects of leflunomide, but not its metabolite A771726, were strongly dependent upon AhR expression. It has been well established that supplementation of cells with exogenous uridine completely rescues the anti-proliferative effects due to DHODH inhibition. Thus, we performed uridine rescue experiments in A375 cells to determine whether the anti-proliferative effects of leflunomide are solely due to DHODH inhibition as previously reported. Interestingly, saturating levels of uridine only modestly rescued A375 cells from the anti-proliferative effects of both leflunomide and A771726, indicating additional mechanism(s), apart from DHODH inhibition are responsible for the anti-proliferative effects of leflunomide in melanoma cells. Uridine also did not rescue MDA-MB-435S melanoma cell proliferation after leflunomide treatment. Our results reveal that the AhR is a molecular target of leflunomide and support the feasibility of the clinical application of leflunomide for treating melanoma. Furthermore, analysis of expression data from 967 cancer cell lines revealed that AhR is expressed in multiple different cancer types supporting the intriguing possibility of targeting the AhR for therapy in a number of cancers.

The anti-inflammatory drug leflunomide is an agonist of the aryl hydrocarbon receptor.

BACKGROUND: The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that mediates the toxicity and biological activity of dioxins and related chemicals. The AhR influences a variety of processes involved in cellular growth and differentiation, and recent studies have suggested that the AhR is a potential target for immune-mediated diseases. METHODOLOGY/PRINCIPAL FINDINGS: During a screen for molecules that activate the AhR, leflunomide, an immunomodulatory drug presently used in the clinic for the treatment of rheumatoid arthritis, was identified as an AhR agonist. We aimed to determine whether any biological activity of leflunomide could be attributed to a previously unappreciated interaction with the AhR. The currently established mechanism of action of leflunomide involves its metabolism to A771726, possibly by cytochrome P450 enzymes, followed by inhibition of de novo pyrimidine biosynthesis by A771726. Our results demonstrate that leflunomide, but not its metabolite A771726, caused nuclear translocation of AhR into the nucleus and increased expression of AhR-responsive reporter genes and endogenous AhR target genes in an AhR-dependent manner. In silico Molecular Docking studies employing AhR ligand binding domain revealed favorable binding energy for leflunomide, but not for A771726. Further, leflunomide, but not A771726, inhibited in vivo epimorphic regeneration in a zebrafish model of tissue regeneration in an AhR-dependent manner. However, suppression of lymphocyte proliferation by leflunomide or A771726 was not dependent on AhR. CONCLUSIONS: These data reveal that leflunomide, an anti-inflammatory drug, is an agonist of the AhR. Our findings link AhR activation by leflunomide to inhibition of fin regeneration in zebrafish. Identification of alternative AhR agonists is a critical step in evaluating the AhR as a therapeutic target for the treatment of immune disorders.

Modeling of the aryl hydrocarbon receptor (AhR) ligand binding domain and its utility in virtual ligand screening to predict new AhR ligands.

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor; the AhR Per-AhR/Arnt-Sim (PAS) domain binds ligands. We developed homology models of the AhR PAS domain to characterize previously observed intra- and interspecies differences in ligand binding using molecular docking. In silico structure-based virtual ligand screening using our model resulted in the identification of pinocembrin and 5-hydroxy-7-methoxyflavone, which promoted nuclear translocation and transcriptional activation of AhR and AhR-dependent induction of endogenous target genes.