Retinoic acid inhibits angiogenesis and tumor growth of thyroid cancer cells

Molecular signatures of angiogenesis inhibitors: a single-embryo untargeted metabolomics approach in zebrafish

Angiogenesis is a key process in embryonic development, a disruption of this process can lead to severe developmental defects, such as limb malformations. The identification of molecular perturbations representative of antiangiogenesis in zebrafish embryo (ZFE) may guide the assessment of developmental toxicity from an endpoint- to a mechanism-based approach, thereby improving the extrapolation of findings to humans. Thus, the aim of the study was to discover molecular changes characteristic of antiangiogenesis and developmental toxicity. We exposed ZFEs to two antiangiogenic drugs (SU4312, sorafenib) and two developmental toxicants (methotrexate, rotenone) with putative antiangiogenic action. Molecular changes were measured by performing untargeted metabolomics in single embryos. The metabolome response was accompanied by the occurrence of morphological alterations. Two distinct metabolic effect patterns were observed. The first pattern comprised common effects of two specific angiogenesis inhibitors and the known teratogen methotrexate, strongly suggesting a shared mode of action of antiangiogenesis and developmental toxicity. The second pattern involved joint effects of methotrexate and rotenone, likely related to disturbances in energy metabolism. The metabolites of the first pattern, such as phosphatidylserines, pterines, retinol, or coenzyme Q precursors, represented potential links to antiangiogenesis and related developmental toxicity. The metabolic effect pattern can contribute to biomarker identification for a mechanism-based toxicological testing.

Increasing adipocyte number and reducing adipocyte size: the role of retinoids in adipose tissue development and metabolism

The rising prevalence of obesity is a grave public health threat. In response to excessive energy intake, adipocyte hypertrophy impairs cellular function and leads to metabolic dysfunctions while de novo adipogenesis leads to healthy adipose tissue expansion. Through burning fatty acids and glucose, the thermogenic activity of brown/beige adipocytes can effectively reduce the size of adipocytes. Recent studies show that retinoids, especially retinoic acid (RA), promote adipose vascular development which in turn increases the number of adipose progenitors surrounding the vascular vessels. RA also promotes preadipocyte commitment. In addition, RA promotes white adipocyte browning and stimulates the thermogenic activity of brown/beige adipocytes. Thus, vitamin A is a promising anti-obesity micronutrient.

Histopathological prognosis of papillary thyroid carcinoma associated with nutritional status of vitamins A and E

BACKGROUND/OBJECTIVES

Experimental and clinical studies have shown that vitamins A and E can inhibit cancer formation and progression. The unfavourable status of these vitamins can represent risk factors for the disease. This study aimed to evaluate the associations between the nutritional status of vitamins A and E (serum levels and dietary intake) and histopathological outcomes in Papillary Thyroid Carcinoma (PTC) patients.

SUBJECTS/METHODS

We applied a cross-sectional study (2017-2018) and quantified retinol (ROH) and α-tocopherol (TOH) serum levels and vitamins dietary intake of 46 PTC patients. Serum vitamins were quantified by high efficiency liquid chromatography and vitamins dietary intake was analyzed by 24-hr dietary recalls.

RESULTS

Patients with lower ROH serum levels were more likely to present lymph node metastasis and/or angiolymphatic invasion (p = 0.025). In addition, higher vitamin A and vitamin E intake are related to the absence of extrathyroidal extension (p = 0.013) and lymph node metastasis (p = 0.007), respectively. Our findings suggest that a ROH serum level greater than 2.65 μmol/L in PTC patients may be a protective factor against the presence of lymph node metastasis and angiolymphatic invasion. In addition, vitamin A and E intake may protect against extrathyroidal extension and lymph node metastasis.

CONCLUSIONS

A favourable nutritional status (higher serum levels and/or intake) of vitamin A and E may be associated with less aggressive tumours in PTC patients.

Translational Research in Retinopathy of Prematurity: From Bedside to Bench and Back Again

Retinopathy of prematurity (ROP), a vascular proliferative disease affecting preterm infants, is a leading cause of childhood blindness. Various studies have investigated the pathogenesis of ROP. Clinical experience indicates that oxygen levels are strongly correlated with ROP development, which led to the development of oxygen-induced retinopathy (OIR) as an animal model of ROP. OIR has been used extensively to investigate the molecular mechanisms underlying ROP and to evaluate the efficacy of new drug candidates. Large clinical trials have demonstrated the efficacy of anti-vascular endothelial growth factor (VEGF) agents to treat ROP, and anti-VEGF therapy is presently becoming the first-line treatment worldwide. Anti-VEGF therapy has advantages over conventional treatments, including being minimally invasive with a low risk of refractive error. However, long-term safety concerns and the risk of late recurrence limit this treatment. There is an unmet medical need for novel ROP therapies, which need to be addressed by safe and minimally invasive therapies. The recent progress in biotechnology has contributed greatly to translational research. In this review, we outline how basic ROP research has evolved with clinical experience and the subsequent emergence of new drugs. We discuss previous and ongoing trials and present the candidate molecules expected to become novel targets.

Isotretinoin does not alter VEGF-A and VEGF-C levels: do retinoids behave differently in dose-dependent and/or in vivo/in vitro conditions?

BACKGROUND

It is seen that various forms of retinoids have different results on VEGF-A and VEGF-C levels when tested at different dosages, in different diseases and under different conditions such as in vivo or in vitro.

OBJECTIVE

To evaluate the effects of isotretinoin on VEGF-A and VEGF-C levels in humans.

METHODS

Blood samples at the third month of the patient group and blood samples of the control group were compared in terms of VEGF-A and VEGF-C concentrations.

RESULTS

No statistically significant difference was observed between the patient group and the control group in terms of VEGF-A and VEGF-C levels.

LIMITATIONS

Most of the patients discontinued treatment and could not reach the required number, the study was converted to case-control.

CONCLUSIONS

We think that 0.5 mg/kg/day isotretinoin has no effect on blood concentrations of VEGF-A and VEGF-C in humans. Therefore, there is a need for studies using isotretinoin in different doses and durations in humans in order to better evaluate its effects.

Retinoic acid signaling in vascular development

Formation of the vasculature is an essential developmental process, delivering oxygen and nutrients to support cellular processes needed for tissue growth and maturation. Retinoic acid (RA) and its downstream signaling pathway is vital for normal pre- and post-natal development, playing key roles in the specification and formation of many organs and tissues. Here, we review the role of RA in blood and lymph vascular development, beginning with embryonic yolk sac vasculogenesis and remodeling and discussing RA's organ-specific roles in angiogenesis and vessel maturation. In particular, we highlight the multi-faceted role of RA signaling in CNS vascular development and acquisition of blood-brain barrier properties.

Expression and regulation of Angiopoietins and their receptor Tie-2 in sika deer antler

The cartilage vascularization and chondrocyte survival are essential for endochondral ossification which occurs in the process of antler growth. Angiopoietins (Ang) is a family of major angiogenic growth factors and involved in regulating the vascularization. However, the expression and regulation of Angs in the antler are still unknown. The aim of this study is to localize the expression of Ang-1, Ang-2 and their receptor Tie-2 in sika deer antler using in situ hybridization and focused on analyzing the regulation of testosterone, estrogen, all-trans-retinoic acid (ATRA) and 9cRA on their expression in antler chondrocytes. The results showed that Ang-1, Ang-2 and Tie-2 were highly expressed in antler chondrocytes. Administration of testosterone to antler chondrocytes led to a notable increase in the expression of Ang-1 and Tie-2, and a reduction in the expression of Ang-2. The similar result was also observed after estrogen treatment. In contrast, ATRA and 9cRA could inhibit the expression of Ang-1 in antler chondrocytes and heighten the expression of Ang-2. Simultaneously, ATRA could downregulate the expression of Tie-2 in antler chondrocytes at 12 and 24 h, while 9cRA upregulate the expression of Tie-2 at 3 and 6 h. Collectively, Ang-1, Ang-2 and Tie-2 are expressed in antler chondrocytes and their expression can be affected by testosterone, estrogen, ATRA and 9cRA.

Restoring Retinoic Acid Attenuates Intestinal Inflammation and Tumorigenesis in APCMin/+ Mice

Chronic intestinal inflammation accompanies familial adenomatous polyposis (FAP) and is a major risk factor for colorectal cancer in patients with this disease, but the cause of such inflammation is unknown. Because retinoic acid (RA) plays a critical role in maintaining immune homeostasis in the intestine, we hypothesized that altered RA metabolism contributes to inflammation and tumorigenesis in FAP. To assess this hypothesis, we analyzed RA metabolism in the intestines of patients with FAP as well as APC^Min/+ mice, a model that recapitulates FAP in most respects. We also investigated the impact of intestinal RA repletion and depletion on tumorigenesis and inflammation in APC^Min/+ mice. Tumors from both FAP patients and APC^Min/+ mice displayed striking alterations in RA metabolism that resulted in reduced intestinal RA. APC^Min/+ mice placed on a vitamin A-deficient diet exhibited further reductions in intestinal RA with concomitant increases in inflammation and tumor burden. Conversely, restoration of RA by pharmacologic blockade of the RA-catabolizing enzyme CYP26A1 attenuated inflammation and diminished tumor burden. To investigate the effect of RA deficiency on the gut immune system, we studied lamina propria dendritic cells (LPDC) because these cells play a central role in promoting tolerance. APC^Min/+ LPDCs preferentially induced Th17 cells, but reverted to inducing Tregs following restoration of intestinal RA in vivo or direct treatment of LPDCs with RA in vitro These findings demonstrate the importance of intestinal RA deficiency in tumorigenesis and suggest that pharmacologic repletion of RA could reduce tumorigenesis in FAP patients. Cancer Immunol Res; 4(11); 917-26. ©2016 AACR.

Identification of compounds that modulate retinol signaling using a cell-based qHTS assay

In vertebrates, the retinol (vitamin A) signaling pathway (RSP) controls the biosynthesis and catabolism of all-trans retinoic acid (atRA), which regulates transcription of genes essential for embryonic development. Chemicals that interfere with the RSP to cause abnormal intracellular levels of atRA are potential developmental toxicants. To assess chemicals for the ability to interfere with retinol signaling, we have developed a cell-based RARE (Retinoic Acid Response Element) reporter gene assay to identify RSP disruptors. To validate this assay in a quantitative high-throughput screening (qHTS) platform, we screened the Library of Pharmacologically Active Compounds (LOPAC) in both agonist and antagonist modes. The screens detected known RSP agonists, demonstrating assay reliability, and also identified novel RSP agonists including kenpaullone, niclosamide, PD98059 and SU4312, and RSP antagonists including Bay 11-7085, LY294002, 3,4-Methylenedioxy-β-nitrostyrene, and topoisomerase inhibitors (camptothecin, topotecan, amsacrine hydrochloride, and idarubicin). When evaluated in the P19 pluripotent cell, these compounds were found to affect the expression of the Hoxa1 gene that is essential for embryo body patterning. These results show that the RARE assay is an effective qHTS approach for screening large compound libraries to identify chemicals that have the potential to adversely affect embryonic development through interference with retinol signaling.

Preparing normal tissue cells for space flight experiments

Deterioration of health is a problem in modern space flight business. In order to develop countermeasures, research has been done on human bodies and also on single cells. Relevant experiments on human cells in vitro are feasible when microgravity is simulated by devices such as the Random Positioning Machine or generated for a short time during parabolic flights. However, they become difficult in regard to performance and interpretation when long-term experiments are designed that need a prolonged stay on the International Space Station (ISS). One huge problem is the transport of living cells from a laboratory on Earth to the ISS. For this reason, mainly rapidly growing, rather robust human cells such as cancer cells, embryonic cells, or progenitor cells have been investigated on the ISS up to now. Moreover, better knowledge on the behavior of normal mature cells, which mimic the in vivo situation, is strongly desirable. One solution to the problem could be the use of redifferentiable cells, which grow rapidly and behave like cancer cells in plain medium, but are reprogrammed to normal cells when substances like retinoic acid are added. A list of cells capable of redifferentiation is provided, together with names of suitable drugs, in this review.

Modeling pain in vitro using nociceptor neurons reprogrammed from fibroblasts

Reprogramming somatic cells from one cell fate to another can generate specific neurons suitable for disease modeling. To maximize the utility of patient-derived neurons, they must model not only disease-relevant cell classes, but also the diversity of neuronal subtypes found in vivo and the pathophysiological changes that underlie specific clinical diseases. We identified five transcription factors that reprogram mouse and human fibroblasts into noxious stimulus-detecting (nociceptor) neurons. These recapitulated the expression of quintessential nociceptor-specific functional receptors and channels found in adult mouse nociceptor neurons, as well as native subtype diversity. Moreover, the derived nociceptor neurons exhibited TrpV1 sensitization to the inflammatory mediator prostaglandin E2 and the chemotherapeutic drug oxaliplatin, modeling the inherent mechanisms underlying inflammatory pain hypersensitivity and painful chemotherapy-induced neuropathy. Using fibroblasts from patients with familial dysautonomia (hereditary sensory and autonomic neuropathy type III), we found that the technique was able to reveal previously unknown aspects of human disease phenotypes in vitro.

Targeting vascular endothelial growth factor (VEGF) pathway in iodine-refractory differentiated thyroid carcinoma (DTC): from bench to bedside

Thyroid cancer is the most common endocrine malignancy, representing 1% of all human malignancies; its incidence has been escalating worldwide during the last decades. In recent years important molecular pathways contributing to tumor progression and worse survival rates have been identified in iodine-refractory differentiated thyroid carcinoma (DTC) with the consequent development of molecular therapeutics to target these specific oncogenic pathways. For example, a positive correlation has been found between expression of vascular endothelial growth factor (VEGF) and a more aggressive phenotype of DTC. This has led to the widespread adoption of VEGF-targeted therapeutics in the preclinical and clinical settings. In this review we will provide an overview of the different aspects of the use of VEGF-pathway-oriented treatments in iodine-refractory DTC with particular focus on future prospects.

CRABP1 provides high malignancy of transformed mesenchymal cells and contributes to the pathogenesis of mesenchymal and neuroendocrine tumors

CRABP1 (cellular retinoic acid binding protein 1) belongs to the family of fatty acid binding proteins. Retinoic acid binding is the only known functional activity of this protein. The role of CRABP1 in human carcinogenesis remains poorly understood. Here, for the first time we demonstrated pro-metastatic and pro-tumorigenic activity of CRABP1 in mesenchymal tumors. Further functional analysis revealed that the pro-tumorigenic effect of CRABP1 does not depend on retinoic acid binding activity. These results suggest that CRABP1 could have an alternative intracellular functional activity that contributes to the high malignancy of transformed mesenchymal cells. Microarray analysis detected CRABP1-mediated alterations in the expression of about 100 genes, including those encoding key regulatory proteins. CRABP1 is ubiquitously expressed in monophasic synovial sarcomas, while in biphasic synovial sarcomas it is expressed uniquely by the spindle cells of the aggressive mesenchymal component. High level of CRABP1 expression is associated with lymph node metastasis and poor differentiation/high grade of pancreatic neuroendocrine tumors (pNETs). Presented data suggest CRABP1 as a promising biomarker of pNETs' clinical behavior. Our results give the first evidence of pro-tumorigenic and pro-metastatic activity of CRABP1 in mesenchymal and neuroendocrine tumors.

TL-118 and gemcitabine drug combination display therapeutic efficacy in a MYCN amplified orthotopic neuroblastoma murine model--evaluation by MRI

Neuroblastoma (NB) is the most common extra-cranial pediatric solid tumor with up to 50% of NB patients classified as having high-risk disease with poor long-term survival rates. The poor clinical outcome and aggressiveness of high-risk NB strongly correlates with enhanced angiogenesis, suggesting anti-angiogenic agents as attractive additions to the currently insufficient therapeutics. TL-118, a novel drug combination has been recently developed to inhibit tumor angiogenesis. In the current study, we used the SK-N-BE (2) cell line to generate orthotopic NB tumors in order to study the combinational therapeutic potential of TL-118 with either Gemcitabine (40 mg/kg; IP) or Retinoic acid (40 mg/kg; IP). We show that TL-118 treatment (n = 9) significantly inhibited tumor growth, increased cell apoptosis, reduced proliferation and extended mouse survival. Moreover, the reciprocal effect of TL-118 and Gemcitabine treatment (n = 10) demonstrated improved anti-tumor activity. The synergistic effect of these drugs in combination was more effective than either TL or Gemcitabine alone (n = 9), via significantly reduced cell proliferation (p<0.005), increased apoptosis (p<0.05) and significantly prolonged survival (2-fold; p<0.00001). To conclude, we demonstrate that the novel drug combination TL-118 has the ability to suppress the growth of an aggressive NB tumor. The promising results with TL-118 in this aggressive animal model may imply that this drug combination has therapeutic potential in the clinical setting.

Unravelling the blood supply to the zebrafish pharyngeal jaws and teeth

We describe the vascular supply to the pharyngeal jaws and teeth in zebrafish, from larval stages to juveniles, using serial high quality semithin sections and 3D reconstructions. We have identified that the arterial blood supply to the last pair of branchial arches, which carries the teeth, issues from the hypobranchial artery. Surprisingly, the arteries supplying the pharyngeal jaws show an asymmetric branching pattern that is modified over ontogeny. Moreover, the blood vessel pattern that serves each jaw can best be described as a sinusoidal cavity encircling the bases of both the functional and replacement teeth. Capillaries branching from this sinusoidal cavity enter the pulp and constitute the intrinsic blood supply to the attached teeth. The role of these blood vessels during tooth development (whether instructive or nutritive) remains to be determined and requires further study. However, we have provided a firm morphological basis that will aid in the interpretation of experiments addressing this question.

Pretherapeutic drug evaluation by tumor xenografting in anaplastic thyroid cancer

BACKGROUND

Despite various attempts at modifying usual treatment modalities, anaplastic thyroid cancer (ATC) is still associated with unfavorable prognosis. Results of preclinical investigations are often of limited transferability to clinical tumor biology. Individualized multimodal treatment regimens, including novel growth-inhibiting drugs, might be a future option.

METHODS

Tumor tissue, freshly prepared from a patient operated for ATC, was xenotransplanted to nude mice. While the patient obtained a hyperfractionated external beam radiation, mice carrying xenotransplanted tumors were randomized (n = 6) and treated by multikinase inhibitors (sorafenib [S]: vascular endothelial growth factor receptor [VEGF-R], platelet derived growth factor receptor, RET; vandetanib [V]: VEGF-R, endothelial growth factor receptor [EGF-R]; and MLN8054 [M]: Aurora kinases [AK]). Antiproliferative, antiangiogenic, and proapoptotic effects were evaluated.

RESULTS

Treatment of successfully xenotransplanted fresh ATC tumor tissue by multikinase inhibitors and aurora kinase inhibitor reduced the tumor volume up to 61% depending on the drug and time of application (3 wk of treatment: 46% [M], 34% [V], 30% [S]; 5 wk of treatment: 61% [S]). Tumor cell proliferation (BrdU) was reduced between 34% and 58% [S] and [V]. Reduction of tumor vascularity was between 67% [V] and 33% [S] and was accompanied by decreased EGF-R/VEGF-R2 receptor activity [V/V,S]. Tumor cell apoptosis (caspase 3 activity) increased up to 2.4-fold [S].

CONCLUSIONS

Successful in vivo evaluation of novel drugs in xenotransplanted fresh tumor tissue allows in-time (while patient receives standard treatment) prospective analysis for possible additional clinical application. However, technical specifications have to be taken into account to obtain stable in vivo tumor growth. Based on the individual results, a tailored clinical drug application seems possible.

Retinoids: novel immunomodulators and tumour-suppressive agents?

Retinoids play important roles in the transcriptional activity of normal, degenerative and tumour cells. Retinoid analogues may be promising therapeutic agents for the treatment of immune disorders as different as type I diabetes and systemic lupus erythematosus. In addition, the use of retinoids in cancer treatment has progressed significantly in the last two decades; thus, numerous retinoid compounds have been synthesized and tested. In this paper, the actual or potential use of retinoids as immunomodulators or tumour-suppressive agents is discussed.

Prenatal retinoic acid improves lung vascularization and VEGF expression in CDH rat

OBJECTIVE

We sought to investigate the effects of antenatal retinoic acid on the pulmonary vasculature and vascular endothelial growth factor (VEGF) and VEGF receptors (VEGFR) expression in a nitrofen-induced congenital diaphragmatic hernia (CDH) model.

STUDY DESIGN

Rat fetuses were exposed to nitrofen at gestational day 9.5 and/or all-trans retinoic acid (ATRA) at gestational days 18.5-20.5. We assessed lung growth, airway, and vascular morphometry. VEGF, VEGFR1, and VEGFR2 expression was analyzed by Western blotting and immunohistochemistry. Continuous data were analyzed by analysis of variance and Kruskal-Wallis test.

RESULTS

CDH decreased lung to body weight ratio, increased mean linear intercept and mean transection length/airspace, and decreased mean airspace cord length. ATRA did not affect lung growth or morphometry. CDH increased proportional medial wall thickness of arterioles while ATRA reduced it. ATRA recovered expression of VEGF and receptors, which were reduced in CDH.

CONCLUSION

Retinoic acid and VEGF may provide pathways for preventing pulmonary hypertension in CDH.

Retinoic acid suppresses growth of lesions, inhibits peritoneal cytokine secretion, and promotes macrophage differentiation in an immunocompetent mouse model of endometriosis

OBJECTIVE

To determine the effects of all-trans-retinoic acid (RA) on establishment and growth of endometrial lesions, peritoneal interleukin-6 (IL-6) and macrophage chemotactic factor-1 (MCP-1) concentrations, and CD38, CD11b, and F4/80 expression on peritoneal macrophages in an immunocompetent mouse model of endometriosis.

DESIGN

Experimental transplantation study using mice.

SETTING

Academic medical center.

ANIMAL(S)

C57BL/6 recipient mice and syngeneic green fluorescent protein transgenic (GFP+) mice.

INTERVENTION(S)

Recipient mice were inoculated with GFP+ minced uterine tissue to induce endometriosis and treated with RA (400 nmol/day) or vehicle for 17 days (3 days before to 14 days after tissue injection).

MAIN OUTCOME MEASURE(S)

Total number of GFP+ implants in recipient mice, number of implants showing visible blood vessels, total volume of established lesions per mouse, concentrations of IL-6 and MCP-1 in peritoneal fluid, and expression of CD11b, F4/80, and CD38 on peritoneal macrophages.

RESULT(S)

Retinoic acid treatment for 17 days reduced the number of implants versus controls and decreased the frequency of lesions with vessels. Peritoneal washings in RA-treated animals had lower concentrations of IL-6 and MCP-1 than controls 3 days after endometrial inoculation and lower levels of IL-6 on day 14 after inoculation. Concomitant with these effects on day 14, CD38, CD11b, and F4/80 were higher on macrophages from RA-treated mice versus controls.

CONCLUSION(S)

The development of endometriotic implants is inhibited by RA. This effect may be caused, at least in part, by reduced IL-6 and MCP-1 production and enhanced differentiation of peritoneal macrophages.

Bexarotene via CBP/p300 induces suppression of NF-κB-dependent cell growth and invasion in thyroid cancer

PURPOSE

Retinoic acid (RA) treatment has been used for redifferentiation of metastatic thyroid cancer with loss of radioiodine uptake. The aim of this study was to improve the understanding of RA resistance and investigate the role of bexarotene in thyroid cancer cells.

EXPERIMENTAL DESIGN

A model of thyroid cancer cell lines with differential response to RA was used to evaluate the biological effects of retinoid and rexinoid and to correlate this with RA receptor levels. Subsequently, thyroid cancer patients were treated with 13-cis RA and bexarotene and response evaluated on radioiodine uptake reinduction on posttherapy scan and conventional imaging.

RESULTS

In thyroid cancer patients, 13-cis RA resistance can be bypassed in some tumors by bexarotene. A decreased tumor growth without differentiation was observed confirming our in vitro data. Indeed, we show that ligands of RARs or RXRs exert different effects in thyroid cancer cell lines through either differentiation or inhibition of cell growth and invasion. These effects are associated with restoration of RARβ and RXRγ levels and downregulation of NF-κB targets genes. We show that bexarotene inhibits the transactivation potential of NF-κB in an RXR-dependent manner through decreased promoter permissiveness without interfering with NF-κB nuclear translocation and binding to its responsive elements. Inhibition of transcription results from the release of p300 coactivator from NF-κB target gene promoters and subsequent histone deacetylation.

CONCLUSION

This study highlights dual mechanisms by which retinoids and rexinoids may target cell tumorigenicity, not only via RARs and RXRs, as expected, but also via NF-κB pathway.

Targeting the proteasome as a promising therapeutic strategy in thyroid cancer

BACKGROUND AND OBJECTIVES

Targeting the ubiquitin-proteasome system by using proteasome inhibitors represents a novel approach for cancer therapy. Anaplastic thyroid cancer (ATC), a subtype of thyroid cancer (TC), fails to respond to conventional TC treatment. Here we investigated the effects of bortezomib on TC in vitro. Further, the study aimed to evaluate its potential for TC treatment in vivo.

METHODS

Three anaplastic (Hth74, C643, Kat4), one follicular (FTC133), and one papillary (TPC1) TC cell lines were used. Antiproliferative, proapoptotic, and transcriptional effects of bortezomib treatment were analyzed in vitro and growth inhibition of ATC xenografts in vivo. Tumor samples were analyzed by Ki67, CD31, caspase-3, and NF-κB immunohistochemistry.

RESULTS

In vitro, bortezomib inhibited proliferation of TC cells (IC(50) 4-10 nM), increased caspase-3 activity and induced cell cycle arrest. NF-κB activity was affected differently. In vivo, bortezomib treatment was effective in reducing tumor volume (up to 74%), accompanied by reduced proliferation (Ki67) and 57% reduced tumor vascularity.

CONCLUSION

Proteasome inhibition is effective in reducing cell growth and inducing apoptosis of ATC in vitro and inhibiting tumor growth and vascularity in vivo. However, the impact on nuclear transcription remains controversial. Clinical evaluation of bortezomib treatment in ATC is warranted.

Emerging therapeutics for advanced thyroid malignancies: rationale and targeted approaches

INTRODUCTION

Thyroid cancer is an emerging public health concern. In the USA, its incidence has doubled in the past decade, making it the eighth most commonly diagnosed neoplasm in 2010. Despite this alarming increase, most thyroid cancer patients benefit from conventional approaches (surgery, radioiodine, radiotherapy, TSH suppression with levothyroxine) and are often cured. Nevertheless, a minority have aggressive tumors resistant to cytotoxic and other historical therapies; these patients sorely need new treatment options.

AREAS COVERED

Herein the biology and molecular characteristics of the common histological types of thyroid cancer are reviewed to provide context for subsequent discussion of recent developments and emerging therapeutics for advanced thyroid cancers.

EXPERT OPINION

Several kinase inhibitors, especially those targeting VEGFR and/or RET, have already demonstrated promising activity in differentiated and medullary thyroid cancers (DTC, MTC). Although of minimal benefit in DTC and MTC, cytotoxic chemotherapy with anti-microtubule agents and/or anthracyclines in combination with intensity-modulated radiation therapy appears to extend survival for patients with locoregionally confined anaplastic thyroid cancer (ATC), but to have only modest benefit in metastatic ATC. Further discovery and development of novel agents and combinations of agents will be critical to further progress in treating advanced thyroid cancers of all histotypes.

Tumor angiogenesis as a target for dietary cancer prevention

Between 2000 and 2050, the number of new cancer patients diagnosed annually is expected to double, with an accompanying increase in treatment costs of more than $80 billion over just the next decade. Efficacious strategies for cancer prevention will therefore be vital for improving patients' quality of life and reducing healthcare costs. Judah Folkman first proposed antiangiogenesis as a strategy for preventing dormant microtumors from progressing to invasive cancer. Although antiangiogenic drugs are now available for many advanced malignancies (colorectal, lung, breast, kidney, liver, brain, thyroid, neuroendocrine, multiple myeloma, myelodysplastic syndrome), cost and toxicity considerations preclude their broad use for cancer prevention. Potent antiangiogenic molecules have now been identified in dietary sources, suggesting that a rationally designed antiangiogenic diet could provide a safe, widely available, and novel strategy for preventing cancer. This paper presents the scientific, epidemiologic, and clinical evidence supporting the role of an antiangiogenic diet for cancer prevention.

Alternative medical treatment for radioiodine-refractory thyroid cancers

Thyroid cancer is one of the most rapidly increasing cancers in many countries. Although most thyroid cancers are differentiated cancers and easily treated with radioiodine (RI), a portion of differentiated and undifferentiated cancers is refractory not only to RI therapy, but also to radiotherapy and chemotherapy. Thus, various alternative therapies have been tested in RI-refractory thyroid cancers. These alternative therapies include two major categories: redifferentiation therapy and recent molecular target therapy. Several clinical trials have investigated these therapies. They demonstrated potential effects of the therapies, although the results have been somewhat limited so far. Thus, the future strategy for undifferentiated thyroid cancers will involve individualized, lesion-specific, and combined therapy. In this review, the basic mechanism of each redifferentiation and molecular target therapy is discussed, and results of recent clinical trials using these therapeutic agents are summarized.

Follow-up of patients treated with retinoic acid for the control of radioiodine non-responsive advanced thyroid carcinoma

During thyroid tumor progression, cellular de-differentiation may occur and it is commonly accompanied by metastatic spread and loss of iodine uptake. Retinoic acid (RA) administration might increase iodine uptake in about 40% of patients, suggesting that RA could be a promising therapeutic option for radioiodine non-responsive thyroid carcinoma, although a prospective study with a long-term follow-up has not been reported. This was a clinical prospective study assessing the value of 13-cis-RA in patients with advanced thyroid carcinoma and its impact on major outcomes such as tumor regression and cancer-related death with a long-term follow-up of patients submitted to radioiodine (¹³¹I) therapy after RA administration. Sixteen patients with inoperable disease and no significant radioiodine uptake on post-therapy scan were selected. Patients were treated orally with 13-cis-RA at a dose of 1.0 to 1.5 mg·kg⁻¹·day⁻¹ for 5 weeks and then submitted to radioiodine therapy (150 mCi) after thyroxine withdrawal. A whole body scan was obtained 5 to 7 days after the radioactive iodine therapy. RECIST criteria were used to evaluate the response. An objective partial response rate was observed in 18.8%, a stable disease rate in 25% and a progression disease rate in 56.2%. Five patients died (62.5%) in the group classified as progression of disease. Progression-free survival rate (PFS) ranged from 72 to 12 months, with a median PFS of 26.5 months. RA may be an option for advanced de-differentiated thyroid cancer, due to the low rate of side effects.

Proteomic approach reveals novel targets for retinoic acid-mediated therapy of thyroid carcinoma

Our previous studies demonstrated that retinoic acid (RA)-induced reduction of both, the key glycolytic enzyme ENO1 and proliferation-promoting c-Myc, resulted in decreased vitality and invasiveness of the follicular thyroid carcinoma cell lines FTC-133 and FTC-238. By employing two-dimensional electrophoresis and mass spectrometry, we identified proteins affected by RA treatment. In addition to previously reported decrease in ENO1 expression, we found that RA led to significantly reduced levels of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), pyruvate kinase isoenzymes M1/M2 (PKM1/M2), peptidyl-prolyl cis-trans isomerase A (PPIA), transketolase (TKT), annexin A2 (ANXA2), glutathione S-transferase P (GSTP1) and peroxiredoxin 2 (PRDX2) as compared to untreated control. The same proteins investigated on thyroid tissues were found to be significantly up-regulated in follicular, papillary and undifferentiated thyroid carcinomas when compared with goiter and adenoma tissues. These findings identify new target proteins for RA-mediated anti-tumor and re-differentiation therapies and provide novel insights into treatments for thyroid carcinoma.

Ardipusilloside I purified from Ardisia pusilla competitively binds VEGFR and induces apoptosis in NCI-H460 cells

The present study was to evaluate the effects of Ardipusilloside I isolated from Ardisia pusilla on the growth, vascular endothelial growth factor receptor (VEGFR) expression and apoptosis of NCI-H460 cell line by MTT, ELISA and flow cytometer, respectively. The docking assay between Ardipusilloside I and VEGFR was studied by Sybyl/Sketch module. The change of microstructure was observed by transmission electron microscope (TEM). DNA fragmentation was visualized by agarose gel electrophoresis. The protein expression of Bax and Bcl-2 was detected by immunohistochemistry (IHC). A series of changes were observed in NCI-H460 cell treated by Ardipusilloside I, including microstructure, DNA fragmentation, protein expression of VEGFR, Bax and Bcl-2. The results showed Ardipusilloside I had a good docking with VEGFR and could inhibit growth and induce apoptosis of NCI-H460 cell in a dose-dependent manner. Cell cycle was significantly stopped at the G(1) phase. Under electronic microscope, the morphology of NCI-H460 cell treated with Ardipusilloside I showed nuclear karyopycnosis, chromatin agglutination and typical apoptotic body. VEGFR and Bcl-2 expression were decreased and Bax expression was increased. In conclusion, all these results demonstrate that Ardipusilloside I has a good docking with VEGFR and has an inhibitory effect on growth of NCI-H460 cell and can induce its apoptosis.

Retinoic acid is a cofactor for translational regulation of vascular endothelial growth factor in human endometrial stromal cells

Vascular endothelial growth factor (VEGF) and endometrial angiogenesis play a critical role in successful embryonic implantation. Despite many studies of the effects of estrogen and progesterone on VEGF expression, its focal regulation at the site of implantation is unknown. Retinoic acid (RA) has been reported to regulate VEGF in a variety of cell types. Because localized RA synthesis occurs within the periimplantation endometrium, we tested the possibility that RA regulates VEGF production in endometrial stromal cells. Using primary and telomerase-immortalized human endometrial stromal cells, we determined that RA alone did not alter constitutive levels of VEGF production, but markedly amplified secretion when the cells were cotreated with activators of VEGF gene transcription (12-O-tetradecanoyl phorbol-13-acetate, TPA; TGF-beta; and IL-1beta). Whereas TPA or TGF-beta alone stimulated VEGF promoter activity and up-regulated mRNA levels, significant protein secretion was detected only after RA was added to the culture systems. Analysis of retinoids in secretory phase endometrial biopsies indicated that endogenous RA accumulated at concentrations sufficient to induce VEGF secretion. Polyribosome profile analysis showed that the addition of RA to transcriptional activators of VEGF shifted the translational suppressed VEGF mRNA transcripts into larger polyribosome complexes engaged in active translation. Although the precise mechanism(s) of the RA effect remains to be defined, it appears to be mediated by reactive oxygen species; the antioxidant N-acetylcysteine inhibited RA+TPA-stimulated secretion of VEGF by more than 80%. Together, our results demonstrate that in human endometrial stromal cells, RA can combine with transcriptional activators of VEGF to augment VEGF secretion through a translational mechanism of action mediated by reactive oxygen species. These findings suggest a link between the spatiotemporal changes of retinoid synthesis in the periimplantation stroma and the capacity to quickly up-regulate focal VEGF secretion needed to induce early angiogenic events of pregnancy.

Vascular endothelial growth factor expression in invasive papillary thyroid carcinoma

BACKGROUND

The vascular endothelial growth factor (VEGF) is a major promoter of endothelial growth and migration. Some studies have shown a correlation between expression of this growth factor and prognosis in several cancers, including well-differentiated thyroid cancer.

AIM

We studied VEGF expression, local invasiveness, and other prognostic factors in papillary thyroid carcinoma (PTC) to test the hypothesis that the expression of VEGF is correlated with the degree of invasion of PTC.

PATIENTS AND METHODS

Clinical and pathological data of 76 patients with PTC were retrospectively reviewed. Group 1 consisted of patients with gross locally invasive tumors, group 2 consisted of patients with only invasion of the thyroid capsule, and group 3 consisted of patients with noninvasive PTC.

RESULTS

VEGF expression was noted within the tumor in all groups of PTC patients but was absent in the surrounding normal tissue. Older patients had higher expression of VEGF than younger patients. The age of patients with strong reaction to VEGF was 46 +/- 14 (mean +/- standard deviation), and that in patients with a weaker reaction was 39 +/- 16 (p < 0.05). Only 20% of patients with a follicular variant of PTC had a strong reaction to VEGF compared with 68% of patients with classical PTC (p < 0.01).

CONCLUSIONS

VEGF expression appears to be an early event in the development of PTC. Whether VEGF expression promotes the progression of PTC is not known, but the answer to this question may be important in view of its greater expression in older patients, a group whose prognosis in PTC is worse.

Anti-angiogenic activity of triptolide in anaplastic thyroid carcinoma is mediated by targeting vascular endothelial and tumor cells

Triptolide is confirmed to suppress angiogenesis of anaplastic thyroid carcinoma. Here we further expound the precise mechanism involved in this activity. Triptolide downregulated nuclear factor kappa B (NF-kappaB) pathway and its targeting genes associated with endothelial cell mobilization in human umbilical vein endothelial cells (HUVECs) and impaired VEGF expression in thyroid carcinoma TA-K cells. Furthermore, both triptolide and the conditioned medium from triptolide-treated TA-K cells (CMT) significantly attenuated proliferation, migration and tube formation of HUVECs. In vivo, triptolide inhibited TA-K cell-induced tumor growth, vascular formation and VEGF expression. Our data establish that triptolide inhibits tumor angiogenesis by the dual action on vascular endothelial cells and tumor cells, thus providing a novel and overall explanation for the anti-angiogenesis action of triptolide. The multicellular targets emphasize triptolide as a high-performance and potential angiogenesis inhibitor.

Nicotinic acid-mediated activation of both membrane and nuclear receptors towards therapeutic glucocorticoid mimetics for treating multiple sclerosis

Acute attacks of multiple sclerosis (MS) are most commonly treated with glucocorticoids, which can provide life-saving albeit only temporary symptomatic relief. The mechanism of action (MOA) is now known to involve induction of indoleamine 2,3-dioxygenase (IDO) and interleukin-10 (IL-10), where IL-10 requires subsequent heme oxygenase-1 (HMOX-1) induction. Ectopic expression studies reveal that even small changes in expression of IDO, HMOX-1, or mitochondrial superoxide dismutase (SOD2) can prevent demyelination in experimental autoimmune encephalomyelitis (EAE) animal models of MS. An alternative to glucocorticoids is needed for a long-term treatment of MS. A distinctly short list of endogenous activators of both membrane G-protein-coupled receptors and nuclear peroxisome proliferating antigen receptors (PPARs) demonstrably ameliorate EAE pathogenesis by MOAs resembling that of glucocorticoids. These dual activators and potential MS therapeutics include endocannabinoids and the prostaglandin 15-deoxy-Δ^12,14-PGJ₂. Nicotinamide profoundly ameliorates and prevents autoimmune-mediated demyelination in EAE via maintaining levels of nicotinamide adenine dinucleotide (NAD), without activating PPAR nor any G-protein-coupled receptor. By comparison, nicotinic acid provides even greater levels of NAD than nicotinamide in many tissues, while additionally activating the PPARγ-dependent pathway already shown to provide relief in animal models of MS after activation of GPR109a/HM74a. Thus nicotinic acid is uniquely suited for providing therapeutic relief in MS. However nicotinic acid is unexamined in MS research. Nicotinic acid penetrates the blood brain barrier, cures pellagric dementia, has been used for over 50 years clinically without toxicity, and raises HDL concentrations to a greater degree than any pharmaceutical, thus providing unparalleled benefits against lipodystrophy. Summary analysis reveals that the expected therapeutic benefits of high-dose nicotinic acid administration far outweigh any known adverse risks in consideration for the treatment of multiple sclerosis.

New perspectives on the treatment of differentiated thyroid cancer

Even though differentiated thyroid carcinoma is a slow growing and usually curable disease, recurrence occurs in 20-40% and cellular dedifferentiation in up to 5% of cases. Conventional chemotherapy and radiotherapy have just a modest effect on advanced thyroid cancer. Therefore, dedifferentiated thyroid cancer represents a therapeutic dilemma and a critical area of research. Targeted therapy, a new generation of anticancer treatment, is planned to interfere with a specific molecular target, typically a protein that is believed to have a critical role in tumor growth or progression. Since many of the tumor-initiation events have already been identified in thyroid carcinogenesis, targeted therapy is a promising therapeutic tool for advanced thyroid cancer. Several new drugs are currently being tested in in vitro and in vivo studies and some of them are already being used in clinical trials, like small molecule tyrosine kinase inhibitors. In this review, we discuss the bases of targeted therapies, the principal drugs already tested and also options of redifferentiation therapy for thyroid carcinoma.

Thyroid-stimulating hormone/cAMP-mediated proliferation in thyrocytes

Current research on thyrotropin-activated proliferation in the thyrocyte needs to be aimed at a better understanding of crosstalk and negative-feedback mechanisms with other proliferative pathways, especially the insulin/IGF-1-induced phosphoinositol-3 kinase pathway and the serum-induced MAPK or Wnt pathways. Convergence of proliferative pathways in mTOR is a hotspot of current research, and combined treatment using double class inhibitors for thyroid cancer may bring some success. New thyroid-stimulating hormone receptor (TSHR)-interacting proteins, a better picture of cAMP targets, a deeper knowledge of the action of the protein kinase A regulatory subunits, especially their interactions with the replication machinery, and a further understanding of mechanisms that lead to cell cycle progression through G₁/S and G₂/M checkpoints are areas that need further elucidation. Finally, massive information coming from microarray data analysis will prompt our understanding of thyroid-stimulating hormone-promoted thyrocyte proliferation in health and disease.

Taspine isolated from Radix et Rhizoma Leonticis inhibits growth of human umbilical vein endothelial cell (HUVEC) by inducing its apoptosis

The present study was to evaluate the effects of taspine isolated from Radix et Rhizoma Leonticsi on the growth and apoptosis of human umbilical vein endothelial cell (HUVEC) line by MTT and flow cytometer, respectively. At the same time, a series of changes were observed in HUVEC treated by taspine, including microstructure, protein expression of bax, bcl-2 and VEGF. The change of microstructure was observed by transmission electron microscope (TEM). The protein expression of bax and bcl-2 was detected by immunohistochemistry (IHC), and VEGF protein secreted was determined by enzyme-linked immunosorbent assay (ELISA). The results showed taspine could inhibit growth and induce apoptosis of HUVEC in a dose-dependent manner. Cell cycle was significantly stopped at the S phase. Under electronic microscope, the morphology of HUVEC treated with taspine showed nuclear karyopycnosis, chromatin agglutination and typical apoptotic body. Bcl-2 and VEGF expressions were decreased and bax expression was increased. All these results demonstrate that taspine has an inhibitory effect on growth of HUVEC and can induce its apoptosis.