Possible effects of plasminogen activator inhibitor-1 on promoting angiogenesis through matrix metalloproteinase 9 in advanced mycosis fungoides

Mycosis fungoides (MF) progresses slowly before advancing to skin tumors followed by lymph node and visceral involvement. Among MF progression, stage IIB is an initial time point of tumor formation in MF. Since MF in tumor stage possess abundant blood vessels, it is important to evaluate the pro-angiogenic factors before and after MF in stage IIB. In this report, we investigated pro-angiogenic soluble factors in MF patients, as well as its pro-angiogenetic effects on tumor cells and stroma cells. We first evaluated the serum levels of pro-angiogenic factors in 9 MF patients without tumor formation and 8 MF patients with tumor formation. Among them, the serum MMP-9 and plasminogen activator inhibitors 1 (PAI-1) was significantly increased in MF with tumor formation compared in MF without tumor formation, leading to favorable formation of human dermal microvascular endothelial cells tube networks. Moreover, PAI-1 stimulation significantly increased the mRNA expression and protein production MMP-9 on monocytes derived M2 macrophages and HUT-78. Furthermore, since MMP-9 production from tumor cells as well as stromal cells is suppressed by bexarotene, we evaluate the baseline serum pro-angiogenic factors including MMP-9 in 16 patients with advanced cutaneous T cell lymphoma treated with bexarotene. The serum levels of MMP-2 and MMP-9 was significantly increased in bexarotene non-responded patients compared to responded patients. Our present study suggested the significance of MMP-9 and PAI-1 for the progression of MF stage toward to the tumor stage, and could be a therapeutic target in future.

Design, synthesis and characterization of a novel multicomponent salt of bexarotene with metformin and application in ameliorating psoriasis with T2DM

Psoriasis is a common systemic inflammatory skin disorder affecting over 60 million people globally. Some patients with psoriasis are associated with a higher risk of type 2 diabetes mellitus (T2DM). Psoriasis and T2DM occur concurrently in some patients; however, there is no effective drug for the treatment of psoriasis with T2DM. Bexarotene (BEX) is a specific RXR agonist and an antineoplastic agent indicated by the FDA for cutaneous T-cell lymphoma (CTLA). Metformin (MET) is the first-line treatment for T2DM. To develop novel effective drugs for the treatment of psoriasis with T2DM, multicomponent salts containing MET and BEX were designed and synthesized based on the drug-drug combination strategy. MET-BEX (1:1) and MET-BEX-H2O (1:1:1) were obtained and structurally characterized. The in vitro evaluation results showed that the hygroscopicity of MET was significantly optimized by the salt formation strategy, while the solubility of BEX was improved, which laid the foundation for improving the bioavailability of BEX in vivo. In a mouse model of imiquimod-induced psoriasis with T2DM, MET-BEX ameliorated imiquimod-induced psoriasis morphological features and systematic inflammation and improved glucolipid metabolism. These results showed that the multicomponent drug combination strategy in this study optimized the physicochemical properties of MET and BEX simultaneously, providing a promising candidate therapy for psoriasis with T2DM.

Structure based virtual screening and molecular simulation study of FDA-approved drugs to inhibit human HDAC6 and VISTA as dual cancer immunotherapy

Cancer immunotherapy has significantly contributed to the treatment of various types of cancers mainly by targeting immune checkpoint inhibitors (ICI). Among them, V-domain immunoglobulin suppressor of T cell activation (VISTA) has been explored as a promising therapeutic target. Besides, histone deacetylase 6 (HDAC6) has been demonstrated to be efficacious target for several cancers. The current theoretical work was performed to explore the virtual repurposing of the FDA-approved drugs as inhibitors against these two (VISTA and HDAC6) cancers therapeutic targets. The crystal structure of the two proteins were downloaded from PDB and subjected to virtual screening by DrugRep webserver while using FDA-approved drugs library as ligands database. Our study revealed that Oxymorphone and Bexarotene are the top-ranked inhibitors of VISTA and HDAC6, respectively. The docking score of Bexarotene was predicted as - 10 kcal/mol while the docking score of Oxymorphone was predicted as - 6.2 kcal/mol. Furthermore, a total of 100 ns MD simulation revealed that the two drugs Oxymorphone and Bexarotene formed stable complexes with VISTA and HDAC6 drug targets. As compared to the standard drug the two drugs Oxymorphone and Bexarotene revealed great stability during the whole 100 ns MD simulation. The binding free energy calculation further supported the Root Mean Square Deviation (RMSD) result which stated that as compared to the ref/HDAC6 (- 18.0253 ± 2.6218) the binding free energy score of the Bexarotene/HDAC6 was good (- 51.9698 ± 3.1572 kcal/mol). The binding free energy score of Oxymorphone/VISTA and Ref/VISTA were calculated as - 36.8323 ± 3.4565, and - 21.5611 ± 4.8581 respectively. In conclusion, the two drugs deserve further consideration as cancer treatment option.

Drug screening identifies tazarotene and bexarotene as therapeutic agents in multiple sulfatase deficiency

Multiple sulfatase deficiency (MSD, MIM #272200) results from pathogenic variants in the SUMF1 gene that impair proper function of the formylglycine-generating enzyme (FGE). FGE is essential for the posttranslational activation of cellular sulfatases. MSD patients display reduced or absent sulfatase activities and, as a result, clinical signs of single sulfatase disorders in a unique combination. Up to date therapeutic options for MSD are limited and mostly palliative. We performed a screen of FDA-approved drugs using immortalized MSD patient fibroblasts. Recovery of arylsulfatase A activity served as the primary readout. Subsequent analysis confirmed that treatment of primary MSD fibroblasts with tazarotene and bexarotene, two retinoids, led to a correction of MSD pathophysiology. Upon treatment, sulfatase activities increased in a dose- and time-dependent manner, reduced glycosaminoglycan content decreased and lysosomal position and size normalized. Treatment of MSD patient derived induced pluripotent stem cells (iPSC) differentiated into neuronal progenitor cells (NPC) resulted in a positive treatment response. Tazarotene and bexarotene act to ultimately increase the stability of FGE variants. The results lay the basis for future research on the development of a first therapeutic option for MSD patients.

Next-generation retinoid X receptor agonists increase ATRA signaling in organotypic epithelium cultures and have distinct effects on receptor dynamics

Retinoid X receptors (RXRs) are nuclear transcription factors that partner with other nuclear receptors to regulate numerous physiological processes. Although RXR represents a valid therapeutic target, only a few RXR-specific ligands (rexinoids) have been identified, in part due to the lack of clarity on how rexinoids selectively modulate RXR response. Previously, we showed that rexinoid UAB30 potentiates all-trans-retinoic acid (ATRA) signaling in human keratinocytes, in part by stimulating ATRA biosynthesis. Here, we examined the mechanism of action of next-generation rexinoids UAB110 and UAB111 that are more potent in vitro than UAB30 and the FDA-approved Targretin. Both UAB110 and UAB111 enhanced ATRA signaling in human organotypic epithelium at a 50-fold lower concentration than UAB30. This was consistent with the 2- to 5- fold greater increase in ATRA in organotypic epidermis treated with UAB110/111 versus UAB30. Furthermore, at 0.2 μM, UAB110/111 increased the expression of ATRA genes up to 16-fold stronger than Targretin. The less toxic and more potent UAB110 also induced more changes in differential gene expression than Targretin. Additionally, our hydrogen deuterium exchange mass spectrometry analysis showed that both ligands reduced the dynamics of the ligand-binding pocket but also induced unique dynamic responses that were indicative of higher affinity binding relative to UAB30, especially for Helix 3. UAB110 binding also showed increased dynamics towards the dimer interface through the Helix 8 and Helix 9 regions. These data suggest that UAB110 and UAB111 are potent activators of RXR-RAR signaling pathways but accomplish activation through different molecular responses to ligand binding.

A novel cell senescence-related IncRNA survival model associated with the tumor immune environment in colorectal cancer

Long noncoding RNAs have a major role in tumorigenesis, development, and metastasis in colorectal cancer (CRC), participate in the regulation of cell senescence and are related to the prognosis of CRC. Therefore, it is important to validate cell senescence-related lncRNAs that correlate with prognosis in CRC.

Isolation of Reporter Cells That Respond to Vitamin A and/or D Using a piggyBac Transposon Promoter-Trapping Vector System

Previously, we established a highly sensitive promoter-trapping vector system using the piggyBac transposon for the efficient isolation of reporter cells. Herein, we examine whether this screening system can be applied to obtain vitamin-responsive cells. As a result, one and two reporter cells that responded to bexarotene (vitamin A) and calcitriol (vitamin D), respectively, were isolated from 4.7 × 106 seeded HeLaS3 cells. 5' RACE analyses identified the well-known CYP24A1 gene as a calcitriol-responsive gene, as well as two new bexarotene- or calcitriol-responsive genes, BDKRB2 and TSKU, respectively. TSKU, interestingly, also responded to bexarotene. Endogenous levels of the TSKU and BDKRB2 transcripts displayed only slight changes and were not detected in the comprehensive analyses performed to date. Dose-response analyses of BDKRB2 and TSKU reporter cells in parallel revealed a differential profile in response to each vitamin A agonist, suggesting a bioanalyzer. The present study demonstrates that producing multiple reporter cells by a type of random screening can efficiently identify novel genes with unusual characteristics and be used for the profiling of the properties of vitamin compounds. Similar approaches to the method shown here may be useful for identifying new markers and for the analysis or diagnosis of nutrients, toxins, metabolites, etc.

Mogamulizumab for Previously Treated Mycosis Fungoides and Sézary Syndrome: An Evidence Review Group Perspective of a NICE Single Technology Appraisal

The National Institute for Health and Care Excellence (NICE) invited the manufacturer (Kyowa Kirin) of mogamulizumab (Poteligeo®), as part of the single technology appraisal process, to submit evidence for its clinical and cost-effectiveness for previously treated mycosis fungoides (MF) and Sézary syndrome (SS). Kleijnen Systematic Reviews Ltd, in collaboration with Maastricht University Medical Centre, was commissioned to act as the independent evidence review group (ERG). This paper summarises the company submission (CS), presents the ERG's critical review of the clinical and cost-effectiveness evidence in the CS, highlights the key methodological considerations and describes the development of the NICE guidance by the Appraisal Committee. Based on a systematic literature review, one randomised controlled trial, MAVORIC, was identified showing favourable results in patients with MF and SS. However, MAVORIC compared mogamulizumab to vorinostat, which is not standard care in the NHS, and there is uncertainty due to the study design, specifically crossover of patients. Based on a "naïve comparison of results from the vorinostat arm of the MAVORIC study and the physician's choice arm (methotrexate or bexarotene i.e. United Kingdom [UK] standard treatments) of the ALCANZA study as well as comparison to Phase II bexarotene data", the company considered vorinostat to be "a reasonable proxy for current standard of care in the NHS". The ERG considered, based on the limited data available, that the comparability of vorinostat (MAVORIC) and physician's choice (ALCANZA) could not be established. In response to the Appraisal Consultation Document, the company provided an unanchored matched adjusted indirect comparison (MAIC) of mogamulizumab with UK standard care by analysing Hospital Episode Statistics (HES) data. However, given the high risk of bias of an unanchored MAIC, these results needed to be regarded with a considerable degree of caution. The economic analysis suffered from uncertainty because there was no trial evidence on the comparator in the England and Wales National Health Service (NHS), and it was unclear to what extent the trial (MAVORIC) comparator (vorinostat) was comparable to standard care, referred to as established clinical management (ECM) in the NHS. The evidence for overall survival had not reached maturity and was confounded by treatment switching, for which different crossover adjustment methods produced large variations in life years. Caregiver utilities were applied in the analysis, but there was a lack of guidance on their application and whether these were indicated in this appraisal. After consultation, the company updated the economic analysis with the MAIC. Incremental cost-effectiveness ratios comparing mogamulizumab against ECM were (depending on whether the HES or MAVORIC comparison were used) £31,030 or £32,634 per quality-adjusted life years (QALYs) gained according to the company's base case and £38,274 or £80,555 per QALY gained according to the ERG's base case. NICE did not recommend mogamulizumab for treating MF or SS in adults who have had at least one previous systemic treatment. This decision was subsequently appealed, and an appeal decision has been reached.

Bexarotene-induced central hypothyroidism assessed by TRH stimulation test in cutaneous T-cell lymphoma patients

Bexarotene-induced central hypothyroidism (CH), for which levothyroxine (LT4) replacement is recommended, has been shown to be caused by pituitary but not hypothalamic disorder experimentally, though the underlying mechanism in humans remains unclear. Here, the pathophysiology of bexarotene-induced CH was examined using a TRH stimulation test in cutaneous T-cell lymphoma (CTCL) patients. In this retrospective longitudinal observational study, serum TSH and free T4 (F-T4) levels were measured in 10 euthyroid patients with CTCL during 24 weeks of bexarotene treatment. TRH stimulation testing was performed following CH diagnosis, with LT4 replacement dosage adjusted to maintain F-T4 at the pre-treatment level. After one week of bexarotene administration, all 10 patients developed CH, based on combined findings of low or low-normal F-T4 with low or normal TSH levels. TSH peak response after a stimulation test at one week was reached at 30 minutes. However, that was <4 μIU/mL in all patients, indicating a blunted though not exaggerated and delayed TSH response. In eight who continued bexarotene for 24 weeks, median LT4 replacement dosage was 125 (range, 75-150) μg/day. TSH level at 30 as well as 15, 60, 90, and 120 minutes after TRH stimulation was significantly correlated with LT4 replacement dosage (ρ = -0.913, p = 0.002), whereas TSH and F-T4 basal levels at one week were not. These results suggest that pituitary hypothyroidism is responsible for bexarotene-induced CH, while TSH levels after TRH stimulation precisely reflect residual pituitary-thyroid function in patients receiving bexarotene.

Potential therapeutic uses of rexinoids

The discovery of nuclear receptors, particularly retinoid X receptors (RXR), and their involvement in numerous pathways related to development sparked interest in their immunomodulatory properties. Genetic models using deletion or overexpression of RXR and the subsequent development of several small molecules that are agonists or antagonists of this receptor support a promising therapeutic role for these receptors in immunology. Bexarotene was approved in 1999 for the treatment of cutaneous T cell lymphoma. Several other small molecule RXR agonists have since been synthesized with limited preclinical development, but none have yet achieved FDA approval. Cancer treatment has recently been revolutionized with the introduction of immune checkpoint inhibitors, but their success has been restricted to a minority of patients. This review showcases the emerging immunomodulatory effects of RXR and the potential of small molecules that target this receptor as therapies for cancer and other diseases. Here we describe the essential roles that RXR and partner receptors play in T cells, dendritic cells, macrophages and epithelial cells, especially within the tumor microenvironment. Most of these effects are site and cancer type dependent but skew immune cells toward an anti-inflammatory and anti-tumor effect. This beneficial effect on immune cells supports the promise of combining rexinoids with approved checkpoint blockade therapies in order to enhance efficacy of the latter and to delay or potentially eliminate drug resistance. The data compiled in this review strongly suggest that targeting RXR nuclear receptors is a promising new avenue in immunomodulation for cancer and other chronic inflammatory diseases.

RXR Negatively Regulates Ex Vivo Expansion of Human Cord Blood Hematopoietic Stem and Progenitor Cells

Ex vivo expansion of human cord blood (CB) hematopoietic stem cells (HSCs) is one approach to overcome limited numbers of HSCs in single CB units. However, there is still no worldwide acceptable HSC ex vivo expansion system. A main reason is that we still have very limited knowldege regarding mechanisms underlying maintenance and expansion of CB HSCs. Here we report that retinoid X receptor (RXR) activity is of significance for CB HSC ex vivo expansion. RXR antagonist HX531 significantly promoted ex vivo expansion of CB HSCs and progenitor cells (HPCs). RXR agonist Bexarotene notably suppressed ex vivo expansion of CB HSCs. Activation of RXR by Bexarotene significantly blocked expansion of phenotypic HSCs and HPCs and expressed increased functional HPCs as assessed by colony formation induced by UM171 and SR1. In vivo transplantation experiments in immune-deficient mice demonstrated that HX531 expanded CB HSCs possess long-term reconstituting capacities, and Bexarotene treatment inhibited expansion of functional CB HSCs. RNA-seq analysis revealed that RXR regulates expression of FBP1 (a negative regulator of glucose metabolism) and many genes involved in differentation. ECAR analysis showed that HX531 significantly promoted glycolytic activity of CB CD34⁺ HSCs and HPCs. Our studies suggest that RXR is a negative regulator of ex vivo expansion of CB HSCs and HPCs.

Inhibition of Androgen Receptor Function and Level in Castration-Resistant Prostate Cancer Cells by 2-[(isoxazol-4-ylmethyl)thio]-1-(4-phenylpiperazin-1-yl)ethanone

The androgen receptor (AR) plays a critical role in the development of castration-resistant prostate cancer (CRPC) as well as in the resistance to the second-generation AR antagonist enzalutamide and the selective inhibitor of cytochrome P450 17A1 (CYP17A1) abiraterone. Novel agents targeting AR may inhibit the growth of prostate cancer cells resistant to enzalutamide and/or abiraterone. Through a high-throughput/high-content screening of a 220,000-member small molecule library, we have previously identified 2-[(isoxazol-4-ylmethyl)thio]-1-(4-phenylpiperazin-1-yl)ethanone (IMTPPE) (SID 3712502) as a novel small molecule capable of inhibiting AR transcriptional activity and protein level in C4-2 prostate cancer cells. In this study, we show that IMTPPE inhibits AR-target gene expression using real-time polymerase chain reaction, Western blot, and luciferase assays. IMTPPE inhibited proliferation of AR-positive, but not AR-negative, prostate cancer cells in culture. IMTPPE inhibited the transcriptional activity of a mutant AR lacking the ligand-binding domain (LBD), indicating that IMTPPE inhibition of AR is independent of the LBD. Furthermore, animal studies showed that IMTPPE inhibited the growth of 22Rv1 xenograft tumor, a model for enzalutamide-resistant prostate cancer. These findings suggest that IMTPPE is a potential lead compound for developing clinical candidates for the treatment of CRPC, including those resistant to enzalutamide.

Molecular dynamics simulations and molecular flooding studies of the retinoid X-receptor ligand binding domain

Bexarotene is an FDA approved retinoid X-receptor (RXR) agonist for the treatment of cutaneous T-cell lymphoma, and its use in other cancers and Alzheimer's disease is being investigated. The drug causes serious side effects, which might be reduced by chemical modifications of the molecule. To rationalize known agonists and to help identify sites for potential substitutions we present molecular simulations in which the RXR ligand-binding domain was flooded with a large number of drug-like molecules, and molecular dynamics simulations of a series of bexarotene-like ligands bound to the RXR ligand-binding domain. Based on the flooding simulations, two regions of interest for ligand modifications were identified: a hydrophobic area near the bridgehead and another near the fused ring. In addition, positional fluctuations of the phenyl ring were generally smaller than fluctuations of the fused ring of the ligands. Together, these observations suggest that the fused ring might be a good target for the design of higher affinity bexarotene-like ligands, while the phenyl ring is already optimized. In addition, notable differences in ligand position and interactions between the RXRα and RXRβ were observed, as well as differences in hydrogen bonding and solvation, which might be exploited in the development of subspecies-specific ligands.

Late-onset bexarotene-induced CD4 lymphopenia in a cutaneous T-cell lymphoma patient

Various infections, autoimmune diseases, medications, and total-body irradiation are known factors associated with CD4 lymphopenia, defined as a CD4 T-cell count below 300 cells/mL or less than 20% of total lymphocytes. We report a rare case of a patient with cutaneous T-cell lymphoma (CTCL) who developed profound CD4 lymphopenia in the setting of long-term bexarotene therapy. Bexarotene is a third-generation retinoid that inhibits epithelial cell proliferation and is approved for treatment of advanced CTCL (stages IIB-IVB) in adult patients who have failed at least 1 prior systemic therapy. This case illustrates the importance of surveillance for CD4 leukopenia in patients on long-term bexarotene therapy with routine complete blood cell counts (CBC) and T-cell counts as well as consideration of rotating patients off bexarotene therapy even in those who derive continuous benefit.

Bexarotene Promotes Cholesterol Efflux and Restricts Apical-to-Basolateral Transport of Amyloid-β Peptides in an In Vitro Model of the Human Blood-Brain Barrier

One of the prime features of Alzheimer's disease (AD) is the excessive accumulation of amyloid-β (Aβ) peptides in the brain. Several recent studies suggest that this phenomenon results from the dysregulation of cholesterol homeostasis in the brain and impaired bidirectional Aβ exchange between blood and brain. These mechanisms appear to be closely related and are controlled by the blood-brain barrier (BBB) at the brain microvessel level. In animal models of AD, the anticancer drug bexarotene (a retinoid X receptor agonist) has been found to restore cognitive functions and decrease the brain amyloid burden by regulating cholesterol homeostasis. However, the drug's therapeutic effect is subject to debate and the exact mechanism of action has not been characterized. Therefore, the objective of this present study was to determine bexarotene's effects on the BBB. Using an in vitro model of the human BBB, we investigated the drug's effects on cholesterol exchange between abluminal and luminal compartments and the apical-to-basolateral transport of Aβ peptides across the BBB. Our results demonstrated that bexarotene induces the expression of ABCA1 but not ApoE. This upregulation correlates with an increase in ApoE2-, ApoE4-, ApoA-I-, and HDL-mediated cholesterol efflux. Regarding the transport of Aβ peptides, bexarotene increases the expression of ABCB1, which in turn decreases Aβ apical-to-basolateral transport. Our results showed that bexarotene not only promotes the cholesterol exchange between the brain and the blood but also decreases the influx of Aβ peptides across BBB, suggesting that bexarotene is a promising drug candidate for the treatment of AD.

Bexarotene protects against traumatic brain injury in mice partially through apolipoprotein E

Bexarotene has been proved to have neuroprotective effects in many animal models of neurological diseases. However, its neuroprotection in traumatic brain injury (TBI) is still unknown. This study aims to explore the neuroprotective effects of bexarotene on TBI and its possible mechanism. Controlled cortical impact (CCI) model was used to simulate TBI in C57BL/6 mice as well as APOE gene knockout (APOE-KO) mice. After CCI, mice were daily dosed with bexarotene or vehicle solution intraperitoneally. The motor function, learning and memory, inflammatory factors, microglia amount, apoptosis condition around injury site and main side-effects were all measured. The results showed that, after CCI, bexarotene treatment markedly improved the motor function and spatial memory in C57BL/6 compare to APOE-KO mice which showed no improvement. The inflammatory cytokines, microglia amount, cell apoptosis rate, and protein of cleaved caspase-3 around the injury site were markedly upregulated after TBI in both C57BL/6 and APOE-KO mice, and all these upregulation were significantly mitigated by bexarotene treatment in C57BL/6 mice, but not in APOE-KO mice. No side-effects were detected after consecutive administration. Taken together, bexarotene inhibits the inflammatory response as well as cell apoptosis and improves the neurological function of mice after TBI partially through apolipoprotein E. This may make it a promising candidate for the therapeutic treatment after TBI.

Tumor stage mycosis fungoides: a single-center study on clinicopathologic features, treatments, and patient outcome

BACKGROUND

Tumor stage mycosis fungoides (MF) is a subtype of cutaneous T-cell lymphoma (CTCL). Tumor stage MF is rarely curable. Treatment is aimed towards controlling the disease and minimizing side effects from therapy.

OBJECTIVE

To characterize clinicopathologic features of tumor stage MF and the impact of clinical characteristics and treatment modalities on patient outcome.

METHODS

A retrospective chart review was conducted on 39 patients with tumor stage MF followed at Vanderbilt University between July 1995 and July 2010.

RESULTS

The median age of diagnosis was 61 years (IQR: 54-70). Sixty-nine percent of the patients were male (27/39). The median follow-up time was 13.6 months (IQR: 5.5-35.9). Among the patients younger than 60 years at the time of initial diagnosis (n = 19), median overall survival (OS) was 7.0 years (95% CI: 2.1-17.9), compared with 3.3 years (95% CI: 2.4-9.3) in patients who were 60 years or older at initial diagnosis. Ten patients with T1/T2 stage at diagnosis had median OS of 5.0 years (95% CI 3.2-7.0). Twenty-eight patients with T3 stage at diagnosis had median OS of 5.8 years (95% CI 2.4-14.2). Median OS for patients with large cell transformation (LCT) and without LCT was 3.3 and 7.7 years, respectively.

LIMITATIONS

This is a retrospective study with the bias of a tertiary-care referral center.

CONCLUSION

Although LCT and older age at diagnosis were not statistically significant negative prognostic indicators of OS, there was a trend towards statistical significance for LCT. Clinical stage at diagnosis may not affect OS in patients who develop tumor stage MF.

Early Treatment Critical: Bexarotene Reduces Amyloid-Beta Burden In Silico

Amyloid-beta peptides have long been implicated in the pathology of Alzheimer's disease. Bexarotene, a drug approved by the U.S. Food and Drug Administration for treating a class of non-Hodgkin's lymphoma, has been reported to facilitate the removal of amyloid-beta. We have developed a mathematical model to explore the efficacy of bexarotene treatment in reducing amyloid-beta load, and simulate amyloid-beta production throughout the lifespan of diseased mice. Both aspects of the model are based on and consistent with previous experimental results. Beyond what is known empirically, our model shows that low dosages of bexarotene are unable to reverse symptoms in diseased mice, but dosages at and above an age-dependent critical concentration can recover healthy brain cells. Further, early treatment was shown to have significantly improved efficacy versus treatment in older mice. Relevance with respect to bexarotene-based amyloid-beta-clearance mechanism and direct treatment for Alzheimer's disease is emphasized.

The influence of bexarotene, a selective agonist of the retinoid receptor X (RXR), and tazarotene, a selective agonist of the retinoid acid receptor (RAR), on bone metabolism in rats

PURPOSE

The purpose of this study was to investigate the influence of selective agonists of the retinoid receptor X (RXR) and the retinoid acid receptor (RAR) on bone metabolism in rats.

METHODS

Thirty six male Wistar rats were divided into three groups: receiving bexarotene, or tazarotene, or to control group. Serum biochemical markers of bone turnover (osteocalcin - OC, tartrate resistant acid phosphatase 5 - TRACP5b and osteoprotegerin - OPG) and mechanical properties of bones were analyzed.

RESULTS

There was a significant decrease in the femur index value in groups receiving tazarotene and bexarotene on Day 14 (8% and 20% respectively, p=0.0039). On Day 28, 14 days after discontinuation of tazarotene and bexarotene, the difference in femur indexes was still significant (4% for T1-6 and B1-6, p=0.0270). In the bexarotene group an increase in mean plasma osteocalcin level and mean plasma TRACP5b level was detected. In the tazarotene group the mean osteocalcin level remained unchanged and the mean plasma TRACP5b level decreased. An increased yield stress was detected in groups receiving retinoids comparing to controls after 14 days of tazarotene and bexarotene administration.

CONCLUSION

Although bexarotene and tazarotene administration caused decrease in the femur index, mechanisms responsible for that effect seem to be different. Our results suggest that bexaroten increases bone turnover. On the contrary, tazaroten seems to have inhibitory effect on bone turnover. A counter influence of selective RAR and RXR agonists on the bone turnover might be the reason for inconsistency in results from published research concerning the influence of retinoids on bone metabolism.

An anticancer drug suppresses the primary nucleation reaction that initiates the production of the toxic Aβ42 aggregates linked with Alzheimer's disease

The conversion of the β-amyloid (Aβ) peptide into pathogenic aggregates is linked to the onset and progression of Alzheimer's disease. Although this observation has prompted an extensive search for therapeutic agents to modulate the concentration of Aβ or inhibit its aggregation, all clinical trials with these objectives have so far failed, at least in part because of a lack of understanding of the molecular mechanisms underlying the process of aggregation and its inhibition. To address this problem, we describe a chemical kinetics approach for rational drug discovery, in which the effects of small molecules on the rates of specific microscopic steps in the self-assembly of Aβ42, the most aggregation-prone variant of Aβ, are analyzed quantitatively. By applying this approach, we report that bexarotene, an anticancer drug approved by the U.S. Food and Drug Administration, selectively targets the primary nucleation step in Aβ42 aggregation, delays the formation of toxic species in neuroblastoma cells, and completely suppresses Aβ42 deposition and its consequences in a Caenorhabditis elegans model of Aβ42-mediated toxicity. These results suggest that the prevention of the primary nucleation of Aβ42 by compounds such as bexarotene could potentially reduce the risk of onset of Alzheimer's disease and, more generally, that our strategy provides a general framework for the rational identification of a range of candidate drugs directed against neurodegenerative disorders.

[Endocrine complications of modern cancer therapy]

Treatment with tyrosine kinase inhibitors leads to thyroid dysfunction in up to one half of treated patients, hypothyroidism being the most common. It is caused by destructive thyroiditis, impaired transport of T4 into the cell and deiodinase induction. Bexarotene is a nuclear retinoid X receptor agonist. Its application is accompanied with central hypothyroidism and hypertriglyceriaemia in virtually all patients and it also increases thyroxin metabolism. Autoimmune endocrine side effects are common in cancer immunotherapy. Cytokines (interpheron α and interleukin 2) cause autoimmune thyroiditis in 2-10 % of treated patients. Therapy with immune checkpoints inhibitors is connected with a variety of immune-related adverse events (irAE). Endocrine irAE include hypophysitis and thyroiditis during treatment with monoclonal antibodies against CTLA4 and thyroid dysfunction during therapy with antibody against CD1 receptor and its ligand. Knowledge, early recognition and management of these side effects is crucial.Key words: bexarotene - endocrine complication - hypophysitis - immune checkpoint inhibitors - immunotherapy.

Retinoid X receptor activation reverses age-related deficiencies in myelin debris phagocytosis and remyelination

The efficiency of central nervous system remyelination declines with age. This is in part due to an age-associated decline in the phagocytic removal of myelin debris, which contains inhibitors of oligodendrocyte progenitor cell differentiation. In this study, we show that expression of genes involved in the retinoid X receptor pathway are decreased with ageing in both myelin-phagocytosing human monocytes and mouse macrophages using a combination of in vivo and in vitro approaches. Disruption of retinoid X receptor function in young macrophages, using the antagonist HX531, mimics ageing by reducing myelin debris uptake. Macrophage-specific RXRα (Rxra) knockout mice revealed that loss of function in young mice caused delayed myelin debris uptake and slowed remyelination after experimentally-induced demyelination. Alternatively, retinoid X receptor agonists partially restored myelin debris phagocytosis in aged macrophages. The agonist bexarotene, when used in concentrations achievable in human subjects, caused a reversion of the gene expression profile in multiple sclerosis patient monocytes to a more youthful profile and enhanced myelin debris phagocytosis by patient cells. These results reveal the retinoid X receptor pathway as a positive regulator of myelin debris clearance and a key player in the age-related decline in remyelination that may be targeted by available or newly-developed therapeutics.

Trimodal Therapy: Combining Hyperthermia with Repurposed Bexarotene and Ultrasound for Treating Liver Cancer

Repurposing of existing cancer drugs to overcome their physical limitations, such as insolubility, represents an attractive strategy to achieve enhanced therapeutic efficacy and broaden the range of clinical applications. Such an approach also promises to offer substantial cost savings in drug development efforts. Here we repurposed FDA-approved topical agent bexarotene (Targretin), currently in limited use for cutaneous manifestations of T-cell lymphomas, and re-engineer it for use in solid tumor applications by forming self-assembling nanobubbles. Physico-chemical characterization studies of the novel prodrug nanobubbles demonstrated their stability, enhanced target cell internalization capability, and highly controlled release profile in response to application of focused ultrasound energy. Using an in vitro model of hepatocellular carcinoma and an in vivo large animal model of liver ablation, we demonstrate the effectiveness of bexarotene prodrug nanobubbles when used in conjunction with catheter-based ultrasound, thereby highlighting the therapeutic promise of this trimodal approach.

Marked lowering of high-density lipoprotein cholesterol levels due to high dose bexarotene therapy

CONTEXT

Bexarotene is a retinoid X receptor agonist, which is currently used for the treatment of cutaneous T-cell lymphoma (CTCL). It is known to induce central hypothyroidism as well as dyslipidemia including elevation of triglycerides (TG) and low-density lipoprotein cholesterol along with slight lowering of high-density lipoprotein cholesterol (HDL-C). Marked lowering of HDL-C has never been previously reported in bexarotene-treated patients and whether it is related to hypothyroidism remains unclear.

CASE REPORT

A 49-year-old African female with a history of CTCL on treatment with bexarotene of 300 mg/d, presented with serum total cholesterol level of 249 mg/dL (6.4 mmol/L), TG level of 92 mg/dL (1.03 mmol/L), HDL-C level of 78 mg/dL (2.02 mmol/L), thyroid stimulating hormone (TSH) of 0.68 μIU/mL, and free thyroxine level of 0.5 ng/dL. Six months later, on increasing the bexarotene dose to 600 mg daily, serum TG increased to 310 mg/dL (3.5 mmol/L) and HDL-C dropped to 3 to 5 mg/dL (0.077-0.13 mmol/L), whereas the TSH was undetectable (0.01 μIU/mL). Despite adequate levothyroxine replacement to 225 μg daily resulting in free thyroxine levels up to 1.5 ng/dL, HDL-C remained extremely low of 4 to 9 mg/dL (0.103-0.233 mmol/L). Bexarotene was discontinued due to poor response of CTCL, 3 months after which her HDL-C levels returned to baseline of 80 to 90 mg/dL (2.07-2.33 mmol/L).

CONCLUSIONS

High dose bexarotene can markedly lower HDL-C levels, which normalize on discontinuation of the drug. Lowering of HDL-C with bexarotene may be due to an increase in cholesterol ester transfer protein activity and appears to be independent of central hypothyroidism.

Combined treatment with bexarotene and rosuvastatin reduces angiotensin-II-induced abdominal aortic aneurysm in apoE(-/-) mice and angiogenesis

BACKGROUND AND PURPOSE

Abdominal aortic aneurysm (AAA) is a degenerative vascular disease associated with angiogenesis. Bexarotene is a retinoid X receptor (RXR) ligand with anti-angiogenic activity. Statins also exert anti-angiogenic activity and activate PPARs. Because RXR ligands form permissive heterodimers with PPARs and a single anti-angiogenic drug may not be sufficient to combat the wide array of angiogenic factors produced during AAA, we evaluated the effect of combined low doses of bexarotene and rosuvastatin in a mouse model of AAA.

EXPERIMENTAL APPROACH

The effect of the combined treatment was investigated in a murine model of angiotensin II-induced AAA in apoE(-/-) mice. This combination therapy was also evaluated in in vivo (Matrigel plug assay) and in vitro (endothelial cell differentiation assay) models of angiogenesis as well as the underlying mechanisms involved.

KEY RESULTS

Co-treatment with bexarotene plus rosuvastatin reduced aneurysm formation, inflammation and neovascularization compared with each single treatment. In HUVEC, the combination of suboptimal concentrations of bexarotene and rosuvastatin inhibited angiotensin II-induced morphogenesis, proliferation and migration. These effects were accompanied by diminished production of pro-angiogenic chemokines (CXCL1, CCL2 or CCL5) and VEGF, and seemed to be mediated by RXRα/PPARα and RXRα/PPARγ activation. This combined therapy reduced the activation of members of the downstream PI3K pathway (Akt/mTOR and p70S6K1) in vivo and in vitro.

CONCLUSIONS AND IMPLICATIONS

The combination of RXR agonists with statins at low doses synergistically interferes with the signalling pathways that modulate inflammation and angiogenesis and may constitute a new and safer therapeutic treatment for the control of AAA.

Activation of the retinoid X receptor modulates angiotensin II-induced smooth muscle gene expression and inflammation in vascular smooth muscle cells

The retinoid X receptor (RXR) partners with numerous nuclear receptors, such as the peroxisome proliferator activated receptor (PPAR) family, liver X receptors (LXRs), and farnesoid X receptor (FXR). Although each heterodimer can be activated by specific ligands, a subset of these receptors, defined as permissive nuclear receptors, can also be activated by RXR agonists known as rexinoids. Many individual RXR heterodimers have beneficial effects in vascular smooth muscle cells (SMCs). Because rexinoids can potently activate multiple RXR pathways, we hypothesized that treating SMCs with rexinoids would more effectively reverse the pathophysiologic effects of angiotensin II than an individual heterodimer agonist. Cultured rat aortic SMCs were pretreated with either an RXR agonist (bexarotene or 9-cis retinoic acid) or vehicle (dimethylsulfoxide) for 24 hours before stimulation with angiotensin II. Compared with dimethylsulfoxide, bexarotene blocked angiotensin II-induced SM contractile gene induction (calponin and smooth muscle-α-actin) and protein synthesis ([(3)H]leucine incorporation). Bexarotene also decreased angiotensin II-mediated inflammation, as measured by decreased expression of monocyte chemoattractant protein-1 (MCP-1). Activation of p38 mitogen-activated protein (MAP) kinase but not extracellular signal-related kinase (ERK) or protein kinase B (Akt) was also blunted by bexarotene. We compared bexarotene to five agonists of nuclear receptors (PPARα, PPARγ, PPARδ, LXR, and FXR). Bexarotene had a greater effect on calponin reduction, MCP-1 inhibition, and p38 MAP kinase inhibition than any individual agonist. PPARγ knockout cells demonstrated blunted responses to bexarotene, indicating that PPARγ is necessary for the effects of bexarotene. These data demonstrate that RXR is a potent modulator of angiotensin II-mediated responses in the vasculature, partially through inhibition of p38.

Evidence of myeloid differentiation in non-M3 acute myeloid leukemia treated with the retinoid X receptor agonist bexarotene

All-trans-retinoic acid has dramatically changed the treatment paradigm for acute promyelocytic leukemia, however, it has no significant activity in non-M3 acute myeloid leukemia (AML). In vitro, bexarotene, a retinoid X receptor agonist inhibits the proliferation of non-M3 AML cell lines and induces differentiation of leukemic blasts from patients. We hypothesized that there may be similar activity in patients with AML. We report on two patients with relapsed or refractory non-M3 AML treated with bexarotene monotherapy. After initiating treatment, both patients showed leukemic differentiation in their peripheral blood and reduction in bone marrow blasts to less than 5%. One patient had a significant improvement in her platelet count with loss of platelet transfusion needs. Differentiation syndrome occurred in one patient and was successfully treated with steroids and discontinuation of bexarotene. These data suggest that bexarotene has clinical activity in non-M3 AML and may be able to induce myeloid differentiation in vivo.

Retinoid X receptor agonists inhibit hypertension-induced myocardial hypertrophy by modulating LKB1/AMPK/p70S6K signaling pathway

BACKGROUND

Retinoid X receptor (RXR) has been demonstrated to play an important role in cardiac development and has been implicated in cardiovascular diseases. This study aimed to examine the effects of RXRα agonist bexarotene on pathological left ventricular hypertrophy (LVH) in a spontaneously hypertensive rat (SHR) model and the underlying mechanism.

METHODS

WKY rats served as controls. SHRs were randomized into 3 groups at the age of 4 weeks and were treated (once daily for 12 weeks) with either bexarotene (30 or 100mg/kg body weight) or vehicle alone. Echocardiography was performed to determine cardiac structure and function. Neonatal cardiomyocytes were treated with AngII (10(-7) mmol/L) with or without the indicated concentration of RXRα ligand 9-cis-RA. The protein abundances of β-actin, RXRα, LKB1, phospho-LKB1, AMPK, phospho-AMPK, P70S6K, phospho-P70S6K, ACE, and AT1 receptor were measured along with blood pressure, body weight and angiotensin II (Ang II) levels. The effects of LKB1 downregulation by LKB1 small, interfering RNA were examined.

RESULTS

Treatment of SHRs with bexarotene resulted in significant inhibition of LVH without eliminating hypertension. Immunoblot with heart tissue homogenates from SHRs revealed that bexarotene activated the LKB1/AMPK signaling pathway and inhibited p70S6K. However, the increased Ang II levels in SHR serum and heart tissue were not reduced by bexarotene treatment. Treatment of cardiomyocytes with Ang II resulted in significantly reduced LKB1/AMPK activity and increased p70S6K activity. 9-cis-RA antagonized Ang II-induced LKB1/AMPK and p70S6K activation changes in vitro.

CONCLUSIONS

RXR agonists prevent the inhibition of the LKB1/AMPK/p70S6K pathway and regulate protein synthesis to reduce LVH. This antihypertrophic effect of bexarotene is independent of blood pressure.

Rexinoids isolated from Sophora tonkinensis with a gene expression profile distinct from the synthetic rexinoid bexarotene

The retinoid X receptor (RXR) plays a critical role in transcriptional regulation via formation of an RXR homodimer or heterodimers with partner nuclear receptors. Despite the numerous beneficial effects, only a limited number of naturally occurring RXR agonists are known. In this report, two prenylated flavanones (1 and 2) isolated from Sophora tonkinensis were identified as new rexinoids that preferentially activated RXRs, relative to the retinoic acid receptor. The activities of 1 and 2 were the most potent among naturally occurring rexinoids, yet 2 orders of magnitude lower than the synthetic rexinoid bexarotene. Compounds 1 and 2 activated particular RXR heterodimers in a manner similar to bexarotene. A microarray assay followed by quantitative real-time polymerase chain reaction analyses on RNAs isolated from C2C12 myotubes treated with 1 or 2 demonstrated that they significantly increased mRNA levels of lipoprotein lipase, angiopoietin-like protein 4, and heme oxygenase-1. In contrast, bexarotene preferentially potentiated transcription of genes involved in lipogenesis and lipid metabolism such as sterol regulatory element-binding protein-1, fatty acid synthase, and apolipoprotein D by a liver X receptor agonist. In this study, we have demonstrated that two newly identified naturally occurring rexinoids, 1 and 2, possess properties different from bexarotene.

Combination of bexarotene and the retinoid CD1530 reduces murine oral-cavity carcinogenesis induced by the carcinogen 4-nitroquinoline 1-oxide

We investigated the effects of bexarotene (a retinoid X receptor agonist), CD1530 (a retinoic acid receptor γ selective agonist), and the combination of these two drugs for the prevention of oral carcinogenesis induced by the carcinogen 4-nitroquinoline 1-oxide (4-NQO) in a mouse model of human oral-cavity and esophageal squamous-cell carcinoma previously generated in our laboratory. We observed decreased numbers of neoplastic tongue lesions and reduced lesion severity in the 4-NQO plus CD1530 (4N+C) and 4-NQO plus bexarotene plus CD1530 (4N+B+C) groups compared with the 4-NQO group. RNA-Seq analyses showed increases in transcripts in cell proliferation/cell cycle progression pathways in the 4-NQO vs. the untreated group. In addition, β-catenin and matrix metallopeptidase 9 (MMP9) protein levels and reactive oxygen species (ROS), as assessed by 4-hydroxynonenal (4-HNE) staining, were elevated in tongue tissues 17 wk after the termination of the 4-NQO treatment. The 4N+B, 4N+C, and 4N+B+C groups showed dramatically lower levels of β-catenin, MMP9, and 4-HNE staining compared with the 4-NQO group. The major reduction in 4-HNE staining in the retinoid treatment groups suggests a novel mechanism of action, reduction of ROS, by which bexarotene and CD1530 inhibit carcinogenesis.

[Effects and related mechanism of retinoid X receptor agonist bexarotene on atherosclerosis progression in diabetic apoE(-/-) mice]

OBJECTIVE

To explore the effect of retinoid X receptor (RXR) agonist bexarotene on atherosclerosis and the potential mechanism in streptozotocin (STZ) induced diabetic apolipoprotein E knockout (apoE(-/-)) mice.

METHODS

Eight C57BL/6 mice served as control, 46 apoE(-/-) mice were randomized into 4 groups: apoE(-/-) group (n = 10), STZ+apoE(-/-) group (n = 12), STZ+apoE(-/-)+Bex 10 (10 mg×kg⁻¹×d⁻¹)group (n = 12), STZ+ apoE(-/-)+Bex 30 (30 mg×kg⁻¹×d⁻¹) group (n = 12). Diabetic apoE(-/-) animal model was established by intraperitoneal injection of STZ. Blood glucose was determined by glucose oxidase method. Patch area in thoracic aorta was measured by HE staining. Western blotting was used to determine the RXR and gp91(phox) protein level in thoracic aorta. Reactive oxygen species (ROS) level in blood and thoracic aorta homogenates was detected by Fenton and Griess method.

RESULTS

(1) Patch areas of thoracic aorta were larger in apoE(-/-) group than in C57BL/6 group [(38.40 ± 8.95)µm² vs. (0.10 ± 0.01) µm², P < 0.01], further increased in STZ+apoE(-/-) group [(94.06 ± 8.04)µm², P < 0.05 vs. apoE(-/-) group] and significantly reduced in STZ+apoE(-/-)+Bex 10 group [(78.72 ± 4.62)µm², P < 0.05 vs. STZ+apoE(-/-) group] and further educed in STZ+apoE(-/-)+Bex 30 group [(46.13 ± 7.56)µm², P < 0.05 vs. STZ+apoE(-/-)+Bex 10 group]. (2) Blood glucose level, TG, TC, LDL-C, thoracic aorta gp91(phox) protein level and ROS level in blood and thoracic aorta homogenates were significantly higher in STZ+apoE(-/-) group than in apoE(-/-) group (all P < 0.05). Blood glucose level and TG, TC, LDL-C levels were similar between STZ+apoE(-/-)+Bex10 and STZ+apoE(-/-) group. Thoracic aorta gp91(phox) protein level and ROS level in blood and thoracic aorta homogenates were lower in STZ+apoE(-/-)+Bex 10 group than in STZ+apoE(-/-) group (P < 0.05). Blood glucose level, TG, TC, LDL-C levels, gp91(phox) expression in thoracic aorta, ROS level in blood and thoracic in STZ+apoE(-/-)+Bex 30 group were lower than in STZ+apoE(-/-) group (all P < 0.05).

CONCLUSION

Bexarotene treatment could attenuate arteriosclerosis progression in STZ induced diabetic apoE(-/-) mice, the underlying mechanism might be related to suppressing oxidative stress and decreasing blood glucose level and improving lipids metabolism.

Endocrine side-effects of anti-cancer drugs: the impact of retinoids on the thyroid axis

Bexarotene (Targretin), approved since 1999 as a second-line treatment for late stage cutaneous T-cell lymphomas, has been shown to induce significant hypothyroidism through TSH suppression. This review revisits, through a case report, mechanisms by which rexinoids repress the expression of TSHB gene as well as αTSH and TRH genes. It appears that rexinoids suppress TSH independently from tri-iodothyronine. Bexarotene also differently affects the gene expression of deiodinases 1 and 2 as well as the peripheral clearance of thyroxine. These data might open new ways of research on the potential interaction between thyroid axis and endogenous rexinoids.

Solubilization of therapeutic agents in micellar nanomedicines

We use atomistic molecular dynamics simulations to reveal the binding mechanisms of therapeutic agents in PEG-ylated micellar nanocarriers (SSM). In our experiments, SSM in buffer solutions can solubilize either ≈11 small bexarotene molecules or ≈6 (2 in low ionic strength buffer) human vasoactive intestinal peptide (VIP) molecules. Free energy calculations reveal that molecules of the poorly water-soluble drug bexarotene can reside at the micellar ionic interface of the PEG corona, with their polar ends pointing out. Alternatively, they can reside in the alkane core center, where several bexarotene molecules can self-stabilize by forming a cluster held together by a network of hydrogen bonds. We also show that highly charged molecules, such as VIP, can be stabilized at the SSM ionic interface by Coulombic coupling between their positively charged residues and the negatively charged phosphate headgroups of the lipids. The obtained results illustrate that atomistic simulations can reveal drug solubilization character in nanocarriers and be used in efficient optimization of novel nanomedicines.

Phase II study of gemcitabine and bexarotene (GEMBEX) in the treatment of cutaneous T-cell lymphoma

BACKGROUND

Both gemcitabine and bexarotene are established single agents for the treatment of cutaneous T-cell lymphoma (CTCL). We investigated the feasibility and efficacy of combining these drugs in a single-arm phase II study.

METHODS

Cutaneous T-cell lymphoma patients who had failed standard skin-directed therapy and at least one prior systemic therapy were given four cycles of gemcitabine and concurrent bexarotene for 12 weeks. Responders were continued on bexarotene maintenance until disease progression or unacceptable toxicity.

RESULTS

The median age was 65 years, stage IB (n=5), stage IIA (n=2), stage IIB (n=8), stage III (n=8) and stage IVA (n=12), 17 patients were erythrodermic, 17 patients were B1, and 10 patients were both erythrodermic and B1. Thirty (86%) patients completed four cycles of gemcitabine. In all, 80.0% of patients demonstrated a reduction in modified Severity-Weighted Assessment Tool (mSWAT) score although the objective disease response rate at 12 weeks was 31% (partial response (PR) 31%) and at 24 weeks 14% (PR 14%, stable disease (SD) 23%, progressive disease (PD) 54%, not evaluable 9%). Median progression-free survival was 5.3 months and median overall survival was 21.2 months.

CONCLUSION

The overall response rate of the combination did not reach the specified target to proceed further and is lower than that previously reported for gemcitabine as a single agent.

Thyroid dysfunction as an unintended side effect of anticancer drugs

BACKGROUND

Several of the currently used anticancer drugs may variably affect thyroid function, with impairment ranging from modified total but not free concentration of thyroid hormones to overt thyroid disease.

SUMMARY

Cytotoxic agents seem to alter thyroid function in a relatively small proportion of adult patients. Anticancer hormone drugs may mainly alter serum levels of thyroid hormone-binding proteins without clinically relevant thyroid dysfunction. Old immunomodulating drugs, such as interferon-α and interleukin-2, are known to induce variably high incidence of autoimmune thyroid dysfunction. Newer immune checkpoint inhibitors, such as anti-CTLA4 monoclonal antibodies, are responsible for a relatively low incidence of thyroiditis and may induce secondary hypothyroidism resulting from hypophysitis. Central hypothyroidism is a well-recognized side effect of bexarotene. Despite their inherent selectivity, tyrosine kinase inhibitors may cause high rates of thyroid dysfunction. Notably, thyroid toxicity seems to be restricted to tyrosine kinase inhibitors targeting key kinase-receptors in angiogenic pathways, but not other kinase-receptors (e.g., epidermal growth factor receptors family or c-KIT). In addition, a number of these agents may also increase the levothyroxine requirement in thyroidectomized patients.

CONCLUSIONS

The pathophysiology of thyroid toxicity induced by many anticancer agents is not fully clarified and for others it remains speculative. Thyroid dysfunction induced by anticancer agents is generally manageable and dose reduction or discontinuation of these agents is not required. The prognostic relevance of thyroid autoimmunity, overt and subclinical hypothyroidism induced by anticancer drugs, the value of thyroid hormone replacement in individuals with abnormal thyrotropin following anticancer systemic therapy, and the correct timing of replacement therapy in cancer patients need to be defined more accurately in well-powered prospective clinical trials.

Quantitative receptor-based imaging of tumor proliferation with the sigma-2 ligand [(18)F]ISO-1

The sigma-2 receptor is expressed in higher density in proliferating (P) tumor cells versus quiescent (Q) tumor cells, thus providing an attractive target for imaging the proliferative status (i.e., P:Q ratio) of solid tumors. Here we evaluate the utility of the sigma-2 receptor ligand 2-(2-[¹⁸F]fluoroethoxy)-N-(4-(3,4-dihydro-6,7-dimethoxyisoquinolin-2(1H)-yl)butyl)-5-methyl-benzamide, [¹⁸F]ISO-1, in two different rodent models of breast cancer. In the first study, small animal Positron Emission Tomography (PET) imaging studies were conducted with [¹⁸F]ISO-1 and ¹⁸FDG in xenografts of mouse mammary tumor 66 and tracer uptake was correlated with the in vivo P:Q ratio determined by flow cytometric measures of BrdU-labeled tumor cells. The second model utilized a chemically-induced (N-methyl-N-nitrosourea [MNU]) model of rat mammary carcinoma to correlate measures of [¹⁸F]ISO-1 and FDG uptake with MR-based volumetric measures of tumor growth. In addition, [¹⁸F]ISO-1 and FDG were used to assess the response of MNU-induced tumors to bexarotene and Vorozole therapy. In the mouse mammary 66 tumors, a strong linear correlation was observed between the [¹⁸F]ISO-1 tumor: background ratio and the proliferative status (P:Q ratio) of the tumor (R = 0.87). Similarly, measures of [¹⁸F]ISO-1 uptake in MNU-induced tumors significantly correlated (R = 0.68, P<0.003) with changes in tumor volume between consecutive MR imaging sessions. Our data suggest that PET studies of [¹⁸F]ISO-1 provide a measure of both the proliferative status and tumor growth rate, which would be valuable in designing an appropriate treatment strategy.

Case experience of 308-nm excimer laser therapy compatibility with PUVA and oral bexarotene for the treatment of cutaneous lesions in mycosis fungoides

Little is known about the safety and effectiveness of excimer laser therapy when used in conjunction with other therapies in the treatment of mycosis fungoides (MF) lesions. We describe the use of adjunctive excimer laser therapy in combination with psoralen plus ultraviolet A (PUVA) and oral bexarotene for the treatment of recalcitrant and sanctuary plaques in a patient with MF. In our patient, this regimen successfully induced clinical and histologic resolution in MF plaques with minimal side effects limited to mild, short-lived tenderness and, rarely, local erythema. Our experience suggests that adjunctive excimer laser therapy with PUVA and oral bexarotene has the potential to be a safe, well-tolerated, and effective focal treatment regimen for cutaneous MF lesions.

Combination treatment in CTCL: the current role of bexarotene

Primary cutaneous T-cell lymphomas are a heterogeneous group of extranodal NH lymphomas primarily presenting in the skin without extracutaneos involvement at diagnosis. Treatment choices closely depend on clinic-pathologic entity and disease stage. Among available choices, oral bexarotene has shown efficacy and safety both in monotherapy and in association with other treatments, by virtue of its versatility and high synergism with alpha-interferon, photochemotherapy (PUVA), and chemotherapy. Moreover, when associated with a wise management of its side effects, bexarotene is well tolerated if used in long-term administration, and it is therefore a good candidate to maintenance treatment after different induction therapies. Recently, the Gruppo Italiano Linfomi Cutanei (GILC) has started some pilot studies, with the aim to investigate bexarotene potential in association with PUVA and single agent chemotherapy (as pegylated liposomal doxorubicin and gemcitabine), and as consolidation/maintenance treatment. The preliminary results of GILC pilot studies confirm the good tolerability and safety of low-intermediate dose bexarotene, and its potential synergism with PUVA and chemotherapy. In addition, its use in consolidation/maintenance has proven efficacy in improving overall response rate.

Woringer-Kolopp disease mimicking foot dermatitis

Woringer-Kolopp disease, also known as localized pagetoid reticulosis, is a rare cutaneous lymphoproliferative disorder classified as a solitary variant of mycosis fungoides (MF). Despite the indolent and benign nature of the disease, misdiagnosis and inappropriate treatment may result in years of debilitating symptoms and even loss of function. We present the case of a patient with long-standing Woringer-Kolopp disease that mimicked foot dermatitis. Histopathologic examination demonstrated epidermotropic infiltration of atypical lymphocytes that were CD3+ CD4- CD8-. The patient was successfully treated with topical keratolytics and bexarotene gel 1% with minimal residual lesions after 8 years of follow-up. We discuss the characteristics of this rare disease in contrast with localized MF as well as more aggressive forms of epidermotropic T-cell lymphoma.

Clinical outcomes and biomarker profiles of elderly pretreated NSCLC patients from the BATTLE trial

BACKGROUND

Treating elderly non-small-cell lung cancer (NSCLC) patients in the salvage setting is challenging because of concerns of intolerance to therapy. Here we report outcomes (survival and toxicity) of elderly patients on the Biomarker-Integrated Approaches of Targeted Therapy for Lung Cancer Elimination (BATTLE) trial.

METHODS

Two hundred and fifty-five chemorefractory NSCLC patients received tumor molecular analysis, and were randomized to erlotinib, erlotinib-bexarotene, vandetanib, or sorafenib. Retrospective subgroup analyses were conducted comparing outcomes among age groups (< 65 versus ≥ 65 years; < 70 versus ≥ 70 years; < 75 versus ≥ 75 years), treatments, and sex.

RESULTS

Median age was 62 years (range, 26-84); 38% were aged 65 years or more. No significant differences among age groups were seen in rates of biopsy-related pneumothorax, treatment-related death, compliance, grade 3 to 4 hematologic toxicities, response rate, nor overall survival. However, older women aged 65 years or more had more grade 3 to 4 nonhematologic toxicities (p = 0.05). Elderly men aged 65 years or more (p = 0.008) had a higher disease-control rate at 8 weeks and a better progression-free survival (PFS) (p = 0.0068). Elderly women aged 70 years or more had a trend toward higher 8-week disease-control rate (p = 0.06). Older men aged 65 years or more treated with vandetanib had a better median PFS (p = 0.03) whereas PFS of older women aged 70 years or more was worse (p = 0.03) compared with younger patients. Elderly men aged 70 years or more treated with sorafenib had a higher overall survival compared with younger men (p = 0.04). Tumor tissue biomarkers show distinct differences by sex and age.

CONCLUSION

Fit elderly NSCLC patients should be considered for salvage targeted therapy. In this subset of patients, older men seem to have significant clinical benefit from certain agents. Tumor biomarker analysis demonstrates sex and age variations, and is hypothesis-generating.

Angiopoietin-like 4 mediates PPAR delta effect on lipoprotein lipase-dependent fatty acid uptake but not on beta-oxidation in myotubes

Peroxisome proliferator-activated receptor (PPAR) delta is an important regulator of fatty acid (FA) metabolism. Angiopoietin-like 4 (Angptl4), a multifunctional protein, is one of the major targets of PPAR delta in skeletal muscle cells. Here we investigated the regulation of Angptl4 and its role in mediating PPAR delta functions using human, rat and mouse myotubes. Expression of Angptl4 was upregulated during myotubes differentiation and by oleic acid, insulin and PPAR delta agonist GW501516. Treatment with GW501516 or Angptl4 overexpression inhibited both lipoprotein lipase (LPL) activity and LPL-dependent uptake of FAs whereas uptake of BSA-bound FAs was not affected by either treatment. Activation of retinoic X receptor (RXR), PPAR delta functional partner, using bexarotene upregulated Angptl4 expression and inhibited LPL activity in a PPAR delta dependent fashion. Silencing of Angptl4 blocked the effect of GW501516 and bexarotene on LPL activity. Treatment with GW501516 but not Angptl4 overexpression significantly increased palmitate oxidation. Furthermore, Angptl4 overexpression did not affect the capacity of GW501516 to increase palmitate oxidation. Basal and insulin stimulated glucose uptake, glycogen synthesis and glucose oxidation were not significantly modulated by Angptl4 overexpression. Our findings suggest that FAs-PPARdelta/RXR-Angptl4 axis controls the LPL-dependent uptake of FAs in myotubes, whereas the effect of PPAR delta activation on beta-oxidation is independent of Angptl4.

Modeling, synthesis and biological evaluation of potential retinoid X receptor-selective agonists: novel halogenated analogues of 4-[1-(3,5,5,8,8-pentamethyl-5,6,7,8-tetrahydro-2-naphthyl)ethynyl]benzoic acid (bexarotene)

The synthesis of halogenated analogues of 4-[1-(3,5,5,8,8-pentamethyl-5,6,7,8-tetrahydro-2-naphthyl)ethynyl]benzoic acid (1), known commonly as bexarotene, and their evaluation for retinoid X receptor (RXR)-specific agonist performance is described. Compound 1 is FDA approved to treat cutaneous T-cell lymphoma (CTCL); however, bexarotene treatment can induce hypothyroidism and elevated triglyceride levels, presumably by disrupting RXR heterodimer pathways for other nuclear receptors. The novel halogenated analogues in this study were modeled and assessed for their ability to bind to RXR and stimulate RXR homodimerization in an RXRE-mediated transcriptional assay as well as an RXR mammalian-2-hybrid assay. In an array of eight novel compounds, four analogues were discovered to promote RXR-mediated transcription with EC(50) values similar to that of 1 and are selective RXR agonists. Our approach also uncovered a periodic trend of increased binding and homodimerization of RXR when substituting a halogen atom for a proton ortho to the carboxylic acid on 1.