A Cross-Cultural Analysis of the COVID-19 Pandemic's Impact on Antenatal Healthcare-Seeking Behaviors in Ghana and the United States

The coronavirus (COVID-19) pandemic impacted healthcare systems worldwide. In this study, we conducted qualitative interviews with pregnant women in Ghana and the United States (US) to understand their antenatal care (ANC) experience. Adapting to the virtual nature of the pandemic, social media platforms Facebook and WhatsApp were used to recruit, consent, enroll, and interview women. Interviewers used a semi-structured guide with content validated by the US and Ghanaian collaborators. Audio recordings of the interviews were transcribed, coded using Dedoose (v8.0.35, Dedoose) and grounded theory, and analyzed for recurring themes. Between May and July 2020, 32 women (15 Ghanaians, 17 Americans), aged 25-40 years were interviewed. Major themes emerged: (i) apprehension about ANC services; (ii) disruptions to planned healthcare provider use; and (iii) changes in social support. Although the women strove to retain their ANC as planned, the pandemic universally caused several unanticipated changes. Given associations between higher maternal mortality and poor outcomes with inadequate ANC, specific policies and resources for telehealth education and intra- and postpartum support should be implemented to reduce disruptions to ANC imposed by COVID-19.

Role of cereblon in angiogenesis and in mediating the antiangiogenic activity of immunomodulatory drugs

Cereblon (CRBN) is a substrate recruiter element of the E3 cullin 4-RING ubiquitin ligase complex, and a binding target of immunomodulatory agents (IMiDs). CRBN is responsible for the pleiotropic effects of IMiDs, yet its function in angiogenesis and in mediating the antiangiogenic effects of IMiDs remains unclear. We investigated the role of CRBN in the angiogenic process and in propagating the antiangiogenic effects of IMiDs in vitro. siRNA-mediated CRBN knock down in human endothelial cells (HUVEC and HMVEC-L), did not affect endothelial cell proliferation, migration, or tube formation. Using CRBN-deficient mice, we further demonstrated that microvessal formation can occur independently of cereblon in the ex vivo mouse aortic ring model. The cereblon E3 ubiquitin ligase complex can recruit endothelial cell-specific factors, AGO2 (associated with angiogenesis), and SALL4 (associated with embryogenesis/angiogenesis), for ubiquitin-mediated degradation. Knockdown of CRBN caused a corresponding increase in AGO2 and SALL4 protein expression and IMiD treatment was able to rescue the siCRBN effect to increase the CRBN expression. These findings suggest one potential mechanism of action that likely involves a tightly coordinated regulation of CRBN with endothelial cell targets and highlight the need to further elucidate the mechanism(s), which could include cereblon-independent pathways, through which IMiDs exert their antiangiogenic effects.

Abstract A069: Mechanisms governing the transcriptional regulation of the liver-specific transporter OATP1B3 in prostate cancer

Background: The testosterone uptake transporter OATP1B3 is expressed de novo in prostate tumors and SLCO1B3 gene (encoding OATP1B3) variants are associated with clinical outcomes in patients with prostate cancer receiving androgen deprivation therapy (ADT) and in castration-resistant disease. These findings support the role of OATP1B3 as a major physiologic contributor to androgen distribution and a contributor to resistance to ADT. We have previously shown CBP/p300-mediated SLCO1B3 expression; however, specific transcriptional regulation of de novo expression remains to be elucidated. We characterized the SLCO1B3 promoter in order to better understand the regulatory mechanisms that govern its expression in prostate cancer. Methods: Functional analysis of the SLCO1B3 promoter was conducted using 5’ deletion mutagenesis. Transcriptional activity of the SLCO1B3 gene was measured using the SLCO1B3 promoter-luciferase reporter plasmids, transient transfections and luciferase reporter assays. Promoter activity was modulated by co-transfection with the p300 expression plasmid or treatment with various p300 inhibitor compounds (chetomin, HATi II, or C646). Results: We detected different transcriptional profiles across multiple prostate cancer cells (22Rv1, LNCaP, PC3) and identified a conserved domain responsible for SLCO1B3 transcriptional activity. Variable transcriptional changes in response to p300 inhibitor treatments were observed in both the conserved domain plasmid and the full-length reporter with the HATi II compound showing a consistent 2 to 3-fold increase in luciferase activity. Putative transcription factor binding sites are being evaluated by site-directed mutagenesis to determine potential regulatory elements involved in transcriptional activity of the gene. Conclusions: Our data suggest that several multi-protein transcription factor complexes assemble at distinct regulatory elements in the SLCO1B3 promoter, driving tissue-specific expression of OATP1B3 in prostate cancer. Understanding the underlying regulatory mechanisms of OATP1B3 expression and the transporter’s role in prostate cancer progression will aid in its development as a potential therapeutic target.

Citation Format: Roberto H Barbier, Edel M McCrea, Jonathan D Strope, Phoebe A Huang, Tristan M Sissung, Douglas K Price, Cindy H Chau, William D Figg. Mechanisms governing the transcriptional regulation of the liver-specific transporter OATP1B3 in prostate cancer [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr A069. doi:10.1158/1535-7163.TARG-19-A069

Botryllamide G is an ABCG2 inhibitor that improves lapatinib delivery in mouse brain

Introduction: Transporters comprising the blood-brain barrier complicate delivery of many therapeutics to the central nervous system. The present study ascertained whether the natural product botryllamide G is viable for in vivo inhibition of ABCG2 using lapatinib as a probe for ABCB1 and ABCG2-mediated efflux from the brain. Methods: Wild-type and Mdr1a/Mdr1b (-/-) mice were treated with botryllamide G and lapatinib ("doublet therapy"), and while a separate cohort of wild-type mice was treated with botryllamide, tariquidar and lapatinib ("triplet therapy"). Results: Botryllamide G demonstrates biphasic elimination with a rapid distribution, decreasing below the in vitro IC50 of 6.9 µM within minutes, yet with a relatively slower terminal half-life (4.6 h). In Mdr1a/Mdr1b (-/-) mice, doublet therapy resulted in a significant increase in brain lapatinib AUC at 8 h (2058 h*ng/mL vs 4007 h*ng/mL; P = .031), but not plasma exposure (P = .15). No significant differences were observed after 24 h. Lapatinib brain exposure was greater through 1 h when wild-type mice were administered triplet therapy (298 h*pg/mg vs 120 h*pg/mg; P < .001), but the triplet decreased brain AUC through 24 h vs. mice administered lapatinib alone (2878 h*pg/mg vs 4461hr*ng/mL; P < .001) and did not alter the brain:plasma ratio. Conclusions: In summary, the ABCG2 inhibitor, botryllamide G, increases brain exposure to lapatinib in mice lacking Abcb1, although the combination of botryllamide G and tariquidar increases brain exposure in wild-type mice only briefly (1 h). Additional research is needed to find analogs of this compound that have better pharmacokinetics and pharmacodynamic effects on ABCG2 inhibition.

Cereblon gene variants and clinical outcome in multiple myeloma patients treated with lenalidomide

Carfilzomib-lenalidomide-dexamethasone (KRd) therapy has yielded promising results in patients with newly diagnosed multiple myeloma (NDMM). Cereblon (CRBN) is the direct molecular target of lenalidomide and genetic polymorphisms in CRBN have been associated with lenalidomide efficacy. In this study, we assessed the correlation of five single nucleotide variants (SNVs) in the CRBN gene with clinical response and outcomes in patients with NDMM administered KRd therapy with lenalidomide maintenance, achieving favorable trial endpoints in a prospective Phase II study (NCT01402284). Of the observed SNVs, no associations with KRd therapy response were found in this patient cohort, although strong trends in hypoalbuminemia grade and hyperbilirubinemia grade emerged across the CRBN rs1672753 genotype (P = 0.0008) and the rs1714327 genotype (P = 0.0010), respectively. Our results do not provide conclusive support for the predictive utility of CRBN gene polymorphisms as potential biomarkers of clinical response to lenalidomide-based therapy in our patient population. However, these findings remain to be validated in prospective studies using larger patient populations.

Abstract 2943: Severe hepatotoxicity of mithramycin therapy caused by altering expression of hepatocellular bile transporters

Mithramycin has shown significant preclinical anticancer activity, but its therapeutic dose is limited by the development of hepatotoxicity that remains poorly characterized. A pharmacogenomics characterization of mithramycin-induced transaminitis revealed that hepatotoxicity is associated with inter-individual variation in genes involved in bile disposition: ABCB4(MDR3) rs2302387 and ABCB11(BSEP) rs4668115 variants reduce transporter expression (P&lt;0.05) and were associated with ≥Grade 3 liver function test (LFT) elevations developing 24 hours after the third infusion of mithramycin (25mcg/kg, 6hr/infusion, qdx7, every 28 days;P&lt;0.0040). A similar relationship was observed in a pediatric cohort genotyped for ABCB11. We therefore undertook to characterize the mechanism of mithramycin-induced acute transaminitis. As mithramycin affects cellular response to bile acid treatment by altering the expression of multiple bile transporters (e.g., ABCB4, ABCB11, NTCP, OSTα/β) in several cell lines (Huh7, HepaRG, HepaRG BSEP (-/-)) and primary human hepatocytes, we hypothesized that mithramycin inhibited bile-mediated activation of the farnesoid X receptor (FXR). FXR was downregulated in all hepatocyte cell lines and primary human hepatocytes (P&lt;0.0001), and mithramycin inhibited CDCA- and GW4046-induced FXR-GAL4 luciferase reporter activity (P&lt;0.001). Mithramycin promoted GCDC-induced cytotoxicity in cells lacking the BSEP transporter and increased the overall intracellular concentration of bile acids in primary human hepatocytes grown in sandwich culture (P&lt;0.01). Mithramycin is an FXR expression and FXR transactivation inhibitor that inhibits bile flow and potentiates bile-induced cellular toxicity, particularly in cells with low BSEP function. These results suggest that mithramycin causes hepatotoxicity through derangement of bile acid disposition; results also suggest that pharmacogenomic markers may be useful to identify patients who may tolerate higher mithramycin doses.

Citation Format: Tristan M. Sissung, Phoebe A. Huang, Ralph Hauke, Edel McCrea, Cody J. Peer, Roberto H. Barbier, Jonathan D. Strope, Ariel M. Ley, Mary Zhang, Julie A. Hong, David Venzon, Jonathan P. Jackson, Kenneth R. Brouwer, Patrick Grohar, John Glod, Brigitte C. Widemann, Theo Heller, David S. Schrump, William D. Figg. Severe hepatotoxicity of mithramycin therapy caused by altering expression of hepatocellular bile transporters [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2943.

Severe Hepatotoxicity of Mithramycin Therapy Caused by Altered Expression of Hepatocellular Bile Transporters

Mithramycin demonstrates preclinical anticancer activity, but its therapeutic dose is limited by the development of hepatotoxicity that remains poorly characterized. A pharmacogenomics characterization of mithramycin-induced transaminitis revealed that hepatotoxicity is associated with germline variants in genes involved in bile disposition: ABCB4 (multidrug resistance 3) rs2302387 and ABCB11 [bile salt export pump (BSEP)] rs4668115 reduce transporter expression (P < 0.05) and were associated with ≥grade 3 transaminitis developing 24 hours after the third infusion of mithramycin (25 mcg/kg, 6 hours/infusion, every day ×7, every 28 days; P < 0.0040). A similar relationship was observed in a pediatric cohort. We therefore undertook to characterize the mechanism of mithramycin-induced acute transaminitis. As mithramycin affects cellular response to bile acid treatment by altering the expression of multiple bile transporters (e.g., ABCB4, ABCB11, sodium/taurocholate cotransporting polypeptide, organic solute transporter α/β) in several cell lines [Huh7, HepaRG, HepaRG BSEP (-/-)] and primary human hepatocytes, we hypothesized that mithramycin inhibited bile-mediated activation of the farnesoid X receptor (FXR). FXR was downregulated in all hepatocyte cell lines and primary human hepatocytes (P < 0.0001), and mithramycin inhibited chenodeoxycholic acid- and GW4046-induced FXR-galactose-induced gene 4 luciferase reporter activity (P < 0.001). Mithramycin promoted glycochenodeoxycholic acid-induced cytotoxicity in ABCB11 (-/-) cells and increased the overall intracellular concentration of bile acids in primary human hepatocytes grown in sandwich culture (P < 0.01). Mithramycin is a FXR expression and FXR transactivation inhibitor that inhibits bile flow and potentiates bile-induced cellular toxicity, particularly in cells with low ABCB11 function. These results suggest that mithramycin causes hepatotoxicity through derangement of bile acid disposition; results also suggest that pharmacogenomic markers may be useful to identify patients who may tolerate higher mithramycin doses. SIGNIFICANCE STATEMENT: The present study characterizes a novel mechanism of drug-induced hepatotoxicity in which mithramycin not only alters farnesoid X receptor (FXR) and small heterodimer partner gene expression but also inhibits bile acid binding to FXR, resulting in deregulation of cellular bile homeostasis. Two novel single-nucleotide polymorphisms in bile flow transporters are associated with mithramycin-induced liver function test elevations, and the present results are the rationale for a genotype-directed clinical trial using mithramycin in patients with thoracic malignancies.

Molecular drivers of metastatic castrate-resistant prostate cancer: New roads to resistance

Numerous growth-inducing signaling pathways have been implicated in the development of metastatic castrate-resistant prostate cancer, but their cross-talk with androgen receptor functions remains poorly understood. A recent study published in Science Signaling by Chen et al.¹ has identified a novel androgen-mediated signaling axis driven by loss of SPDEF and gain of TGFBI to facilitate metastasis, which may explain the acquisition of resistance to androgen deprivation therapy. These findings suggest that therapeutic inhibition of androgen signaling may inadvertently promote castrate resistance by inhibiting tumor suppressive functions of the androgen receptor.