Retinoic acid and retinoid receptors: potential chemopreventive and therapeutic role in cervical cancer

Reverse pharmacology based clinical protocols for noninvasive integrative management of low grade cervical precancer lesions: Rationale and outcomes

Prevention is the most efficient and cost-effective method to combat cervical cancer for which High Risk Human Papilloma Virus (HR-HPV) infection is identified as the major causative factor. HPV vaccination is for primary prevention whereas surgical ablation of precancer is for secondary prevention after HPV infection has occurred. Screening of women for early detection of Squamous Intraepithelial Lesions (SILs) with Papanicolou smear (Pap smear) is a desirable pre-requisite. Surgical ablation which invites invasive procedures is not accessible nor affordable to the larger section of the population. We propose here a non-invasive integrative management approach for the early phase of cervical pre-cancer. In tune with the reverse pharmacology approach, 'experience-exploration- experimentation', we have conducted five clinical studies related to Turmeric extracts for chemo-preventive activity and non-surgical feasibility. We were able to achieve arrest or regression in Low-grade SILs in all 41 women participating in these studies. The unique features of this integrative management approach were i) Avoidance of surgery-associated trauma, cost and complications ii) Standard of care for associated genital infections iii) Feasibility when surgery was not accessible iv) Scope for repeating the noninvasive treatment.

A Scoping Review of Complementary and Alternative Medicine for Human Papillomavirus Infections and Cervical Dysplasia

OBJECTIVE

The goal of this scoping review is to synthesize clinically relevant scientific literature on current complementary and alternative medications that address human papillomavirus (HPV) infections and cervical dysplasia.

MATERIALS AND METHODS

A systematic search of published studies was performed December 2021 for the following concepts: human papilloma virus, cervical dysplasia, and complementary and alternative medicine (CAM). Relevant publications were identified by searching Ovid MEDLINE ALL, Embase, Cochrane Library, AMED, and MEDLINE databases, in addition to clinical trial databases. Data were extracted based on specific study selection criteria and analyzed by 3 authors independently using Covidence software.

RESULTS

A total of 2324 studies were identified of which 56 met inclusion criteria. Treatment outcomes measured regression of HPV, improvement of cervical cytology, and/or regression of histopathology with varied definitions of success across all studies. The CAM therapies found to have the most clinical benefit and best supporting data via randomized control trials were topical mushroom ( Coriolus versicolor) gel, oral and topical selenium therapies, and oral indol-3-carbinol. Adverse events were reported in only 28/56 (50%) of included studies.

CONCLUSIONS

The evidence for treating HPV and cervical dysplasia with CAM is of low quality because of lack of standardized, clinically relevant treatment outcomes, lack of standardization of products, and minimal reporting on adverse and long-term effects. Future large, randomized control trials are needed to further assess efficacy and safety of CAM therapies to address HPV and cervical dysplasia.

Single-cell transcriptomics dissects epithelial heterogeneity in HPV+ cervical adenocarcinoma

The intra- and intertumoral heterogeneity of epithelial cells in human papillomavirus (HPV⁺ ) cervical adenocarcinoma (CEAD) remains largely unknown. To investigate this issue, we performed single-cell RNA sequencing on 19 229 epithelial cells sorted from three tumor samples of three patients with HPV⁺ CEAD. Six epithelial subclusters (Epi1-Epi6) were identified that showed distinct gene expression. Among these, Epi1 and Epi4 had apparent tumor hallmarks and metabolic activities. Epi1 was highly enriched in hallmarks of hypoxia, IL2/STAT5 signaling, retinol metabolism, glycolysis, and arachidonic acid metabolism, while Epi4 was highly enriched in hallmarks of G2M checkpoint, E2F targets, DNA repair, PI3K/AKT/MTOR signaling, glycolysis, fatty acid degradation, TCA cycle, and glutathione metabolism. We also investigated intertumoral epithelial heterogeneity and found that Patient 1 was highly enriched for KRAS signaling and angiogenesis, while Patient 2 was highly enriched for epithelial-mesenchymal transition and TGF-β signaling, and Patient 3 was highly enriched for hypoxia, DNA repair, G2M checkpoint, and E2F targets. Using single-cell RNA sequencing, we revealed the intra- and intertumoral heterogeneity of epithelial cells in HPV⁺ CEAD, providing insights into the importance of personalized treatment for patients with HPV⁺ CEAD.

Novel Self-Assembled Micelles With Increased Tumor Penetration and Anti-Tumor Efficiency Against Breast Cancer

PURPOSE

Recently, docetaxel (DTX) micelles based on retinoic acid derivative surfactants showed lower systemic toxicity and bioequivalence to polysorbate-solubilized docetaxel (Taxotere®) in a phase II clinical study. However, the poor stability of these surfactants in vitro and in vivo led to extremely harsh storage conditions with methanol, and the formed micelles were quickly disintegrated with rapid drug burst release in vivo. To further enhance the stability and accumulation in tumors of DTX micelles, a novel surfactant based on acitretin (ACMeNa) was synthesized and used to prepare DTX micelles to improve anti-tumor efficiency.

METHODS

Novel micelle-forming excipients were synthesized, and the micelles were prepared using the thin film hydration technique. The targeting effect in vitro, distribution in the tumor, and its mechanism were observed. Pharmacokinetics and anti-tumor effect were further investigated in rats and tumor-bearing female mice, respectively.

RESULTS

The DTX-micelles prepared with ACMeNa (ACM-DTX) exhibited a small size (21.9 ± 0.3 nm), 39% load efficiency, and excellent stability in vitro and in vivo. Long circulation time, sustained and steady accumulation, and strong penetration in the tumor were observed in vivo, contributing to a better anti-tumor effect and lower adverse effects.

CONCLUSIONS

The micelles formed by ACMeNa showed a better balance between anti-tumor and adverse effects. It is a promising system for delivering hydrophobic molecules for cancer therapy.

Investigation of miR-21-5p Key Target Genes and Pathways in Head and Neck Squamous Cell Carcinoma Based on TCGA Database and Bioinformatics Analysis

Aim: Head and neck squamous cell carcinoma (HNSCC) is the sixth most commonly diagnosed malignancy worldwide. Overexpressed of microRNA-21-5p (miR-21-5p) has been reported to be involved in the development of HNSCC. However, the role of miR-21-5p in HNSCC is still not fully elucidated. The purpose of this study was to explore the underlying molecular mechanisms of miR-21-5p in HNSCC. Methods: RT-qPCR was used to determine the differential expression levels of miR-21-5p in tissue samples of HNSCC patients. Meta-analysis was performed based on miRNA expression data collected from the Gene Expression Omnibus (GEO) database, The Cancer Genome Atlas (TCGA), and published articles to evaluate the expression of miR-21-5p in HNSCC. We investigated the biological function of miR-21-5P by gene ontology enrichment and target prediction analysis. Furthermore, RT-qPCR and IHC were conducted to verify the expression of target genes. Finally, Kaplan–Meier survival analysis was performed to assessed the prognostic value of the putative miR-21-5p target genes. Results: MiR-21-5p was significantly overexpressed in HNSCC compared to healthy tissues (P < .05) and showed potent predictive power with a summary receiver operating characteristic of 0.90. Meanwhile, the expression of miR-21-5p was significantly correlated with tumor stage, T stage and smoking in HNSCC (P < .05). A total of 71 down-regulated genes, both HNSCC-related and miR-21-p5-related, were obtained from the analytical integration. Two predicted genes (ADH7, RDH12) were down-regulated in HNSCC, and significantly negatively correlated with miR-21-5p. IHC and RT-qPCR demonstrated that the expression of ADH7 and RDH12 in HNSCC samples was significantly lower than control. And high expression of ADH7 was associated with better DFS of HNSCC patients. Conclusions: miR-21-5p may target at ADH7, RDH12 and participate in regulation of retinol metabolism, which might affect the prognosis of HNSCC. High expression of ADH7 may indicate better prognosis in HNSCC patients.

A Comprehensive Review of the Use of Antioxidants and Natural Products in Cancer Patients Receiving Anticancer Therapy

Cancer is the leading cause of mortality and morbidity worldwide. The side effects of cancer treatment affect the quality of life. Cancer patients search for antioxidant dietary supplements and natural products during or after conventional cancer treatment for the alleviation of side effects, improvement of the benefits of treatment, and promotion of well-being. However, the efficacy and safety of these products remain controversial; moreover, previous data do not support the standardized use of those alternative treatments in clinics. The current study reviewed the manuscripts reporting the administration of antioxidants and natural products during cancer treatment and revised preclinical and clinical studies on various types of cancer. Most of the positive results were obtained from experimental animal models; however, human clinical studies are discouraging in this regard. Therefore, further precise and distinguishable studies are required regarding antioxidant dietary supplementation. Future studies are also needed to clarify dietary supplements' mechanism of action and pharmacokinetics in a suitable cancer patient population that will benefit the therapeutic regimens. Despite the popularity of dietary supplements, clinicians and patients should always consider their potential benefits and risks. Patients should discuss with their physician before taking any dietary antioxidant supplements or natural products.

Low-Dose Acitretin for Secondary Prevention of Keratinocyte Carcinomas in Solid-Organ Transplant Recipients

BACKGROUND

Keratinocyte carcinomas, particularly squamous cell carcinoma (SCC), occur more frequently and aggressively in solid-organ transplant recipients (SOTRs) than in the general population. Systemic retinoids are effective in secondary prevention of keratinocyte carcinomas in this population, but their use is limited by adverse effects including a rebound effect in cases of treatment discontinuation.

OBJECTIVE

Our aim was to determine whether low-dose acitretin is efficient in the secondary prevention of keratinocyte carcinomas in SOTRs.

METHODS

This retrospective case-crossover study was conducted at a specialized dermatology clinic for SOTRs in a large transplantation center in 2010-2017. Patients with at least 1 previous keratinocyte carcinoma who were treated with acitretin 10 mg/day for 2 years were included. The main outcome was the difference in the number of new keratinocyte carcinomas diagnosed during treatment compared to during the 2-year pretreatment period.

RESULTS

The cohort included 34 SOTRs. A significant reduction in the mean number of new keratinocyte carcinomas during treatment relative to the pretreatment period was observed (1.7 vs. 3.6, -53% p = 0.002). Similar results were noted on analysis by tumor type, for both SCC and basal cell carcinoma.

CONCLUSION

This study of SOTRs demonstrated positive results for low-dose acitretin as a chemoprevention of keratinocyte carcinomas in this population.

Retinoic Acid Inhibits Tumor-Associated Mesenchymal Stromal Cell Transformation in Melanoma

Bone marrow mesenchymal stem/stromal cells (BMSCs) can be transformed into tumor-associated MSCs (TA-MSCs) within the tumor microenvironment to facilitate tumor progression. However, the underline mechanism and potential therapeutic strategy remain unclear. Here, we explored that interleukin 17 (IL-17) cooperating with IFNγ transforms BMSCs into TA-MSCs, which promotes tumor progression by recruiting macrophages/monocytes and myeloid-derived suppressor cells (MDSCs) in murine melanoma. IL-17 and IFNγ transformed TA-MSCs have high expression levels of myelocyte-recruiting chemokines (CCL2, CCL5, CCL7, and CCL20) mediated by activated NF-κB signaling pathway. Furthermore, retinoic acid inhibits NF-κB signaling, decreases chemokine expression, and suppresses the tumor-promoting function of transformed TA-MSCs by prohibiting the recruitment of macrophages/monocytes and MDSCs in the tumor microenvironment. Overall, our findings demonstrate that IL-17 collaborating with IFNγ to induce TA-MSC transformation, which can be targeted by RA for melanoma treatment.

ADH7, miR-3065 and LINC01133 are associated with cervical cancer progression in different age groups

The aim of the present study was to identify potential therapeutic targets that serve crucial roles in the progression of cervical cancer. Clinical data, RNA sequencing (RNAseq)-counts and micro (mi)RNA data regarding cervical squamous cell carcinoma were retrieved from The Cancer Genome Atlas, and analyses were performed using the University of California Santa Cruz database. RNAseq and miRNA data were stratified into 3 groups (according to the patients' age), and genes were re-annotated and preprocessed prior to Mfuzz time clustering analysis. Subsequently, enrichment analyses were performed in order to identify differentially expressed mRNAs (DEmRNAs) and a protein-protein interaction analysis network was constructed. miRNA-gene, miRNA-lncRNA, and long non-coding (lnc)RNA-mRNA pairs were collected and the lncRNA-miRNA-mRNA competing endogenous (ce)RNA network was established. Further enrichment analyses were performed in order to identify crucial mRNAs in the ceRNA network. Finally, survival and drug association analyses were implemented. A total of 269 DEmRNAs [including alcohol dehydrogenase 7 (ADH7), vestigial-like family member 3 (VGLL3) and cytochrome P450, family 26, subfamily B, polypeptide 1 (CYP26B1)], 274 DElncRNAs (including LINC01133) and 16 DEmiRNAs (including miR-3065 and miR-330) were identified. There were 102 lncRNAs, 15 miRNAs, 15 mRNAs and 522 interaction pairs in the ceRNA network. In particular, ADH7 was regulated by miR-3065, and miR-3065 interacted with LINC01133 in the ceRNA network. Furthermore, ADH7 and CYP26B1 were enriched in the retinoic acid metabolic process and the retinol metabolism pathway. ADH7 and VGLL3 were significantly associated with the cervical cancer survival rate. ADH7, VGLL3, CYP26B1, miR-3065, miR-330, miR-499a and LINC01133 play pivotal roles in the progression of cervical cancer in different age groups.

Targeting Angiogenesis by Blocking the ATM-SerRS-VEGFA Pathway for UV-Induced Skin Photodamage and Melanoma Growth

Retinoic acid (RA) has been widely used to protect skin from photo damage and skin carcinomas caused by solar ultraviolet (UV) irradiation, yet the mechanism remains elusive. Here, we report that all-trans retinoic acid (tRA) can directly induce the expression of a newly identified potent anti-angiogenic factor, seryl tRNA synthetase (SerRS), whose angiostatic role can, however, be inhibited by UV-activated ataxia telangiectasia mutated (ATM) kinase. In both a human epidermal cell line, HaCaT, and a mouse melanoma B16F10 cell line, we found that tRA could activate SerRS transcription through binding with the SerRS promoter. However, UV irradiation induced activation of ATM-phosphorylated SerRS, leading to the inactivation of SerRS as a transcriptional repressor of vascular endothelial growth factor A (VEGFA), which dampened the effect of tRA. When combined with ATM inhibitor KU-55933, tRA showed a greatly enhanced efficiency in inhibiting VEGFA expression and a much better protection of mouse skin from photo damage. Also, we found the combination greatly inhibited tumor angiogenesis and growth in mouse melanoma xenograft in vivo. Taken together, tRA combined with an ATM inhibitor can greatly enhance the anti-angiogenic activity of SerRS under UV irradiation and could be a better strategy in protecting skin from angiogenesis-associated skin damage and melanoma caused by UV radiation.

Binding partners of NRF2: Functions and regulatory mechanisms

NRF2 is a redox-sensitive transcription factor that plays an important role in protecting organisms against diverse types of electrophiles or oxidants. The level of NRF2 is maintained low in normal cells, but highly elevated in cancer provoking chemoresistance or radioresistance. It is now recognized that NRF2 does not merely maintain the redox balance, but also plays significant roles in autophagy, apoptosis, cell cycle progression, and stem cell differentiation, all of which could be possibly attributable to the existence of multiple binding proteins. In the present manuscript, we summarize direct binding partners of NRF2 and illustrate how they bind to NRF2 and regulate its stability or activity.

Immune Signature-Based Subtypes of Cervical Squamous Cell Carcinoma Tightly Associated with Human Papillomavirus Type 16 Expression, Molecular Features, and Clinical Outcome

Substantial heterogeneity exists within cervical cancer that is generally infected by human papillomavirus (HPV). However, the most common histological subtype of cervical cancer, cervical squamous cell carcinoma (CSCC), is poorly characterized regarding the association between its heterogeneity and HPV oncoprotein expression. We filtered out 138 CSCC samples with infection of HPV16 only as the first step; then we compressed HPV16 E6/E7 expression as HPV_pca and correlated HPV_pca with the immunological profiling of CSCC based on supervised clustering to discover subtypes and to characterize the differences between subgroups in terms of the HPV_pca level, pathway activity, epigenetic dysregulation, somatic mutation frequencies, and likelihood of responding to chemo/immunotherapies. Supervised clustering of immune signatures revealed two HPV16 subtypes (namely, HPV16-IMM and HPV16-KRT) that correlated with HPV_pca and clinical outcomes. HPV16-KRT is characterized by elevated expression of genes in keratinization, biological oxidation, and Wnt signaling, whereas HPV16-IMM has a strong immune response and mesenchymal features. HPV16-IMM exhibited much more epigenetic silencing and significant mutation at FBXW7, while MUC4 and PIK3CA were mutated frequently for HPV16-KRT. We also imputed that HPV16-IMM is much more sensitive to chemo/immunotherapy than is HPV16-KRT. Our characterization tightly links the expression of HPV16 E6/E7 with biological and clinical outcomes of CSCC, providing valuable molecular-level information that points to decoding heterogeneity. Together, these results shed light on stratifications of CSCC infected by HPV16 and shall help to guide personalized management and treatment of patients.

The success and the challenge of all-trans retinoic acid in the treatment of cancer

All-trans retinoic acid (ATRA), an active metabolite of vitamin A, plays important roles in cell proliferation, cell differentiation, apoptosis, and embryonic development. The effects of ATRA are mediated by nuclear retinoid receptors as well as non-genomic signal pathway, such as MAPK and PKA. The great success of differentiation therapy with ATRA in acute promyelocytic leukemia (APL) not only improved the prognosis of APL but also spurred the studies of ATRA in the treatment of other tumors. Since the genetic and physiopathological simplicity of APL is not common in human malignancies, the combination of ATRA with other agents (chemotherapy, epigenetic modifiers, and arsenic trioxide, etc) had been extensively investigated in a variety of tumors. In this review, we will discuss in details about ATRA and its role in cancer treatment.

The Thyroid Na+/I- Symporter: Molecular Characterization and Genomic Regulation

Iodide (I-) is an essential constituent of the thyroid hormones triiodothyronine (T₃) and thyroxine (T₄), and the iodide concentrating mechanism of the thyroid gland is essential for the synthesis of these hormones. In addition, differential uptake of iodine isotopes (radioiodine) is a key modality for the diagnosis and therapy of thyroid cancer. The sodium dependent iodide transport activity of the thyroid gland is mainly attributed to the functional expression of the Na+/I- Symporter (NIS) localized at the basolateral membrane of thyrocytes. In this paper, we review and summarize current data on molecular characterization, on structure and function of NIS protein, as well as on the transcriptional regulation of NIS encoding gene in the thyroid gland. We also propose that a better and more precise understanding of NIS gene regulation at the molecular level in both healthy and malignant thyroid cells may lead to the identification of small molecule candidates. These could then be translated into clinical practice for better induction and more effective modulation of radioiodine uptake in dedifferentiated thyroid cancer cells and in their distant metastatic lesions.

Retinoic acid metabolism proteins are altered in trichoblastomas induced by mouse papillomavirus 1

Skin cancer burden is significant as treatment costs have skyrocketed to $8.1 million annually and some forms metastasize, such as cutaneous squamous cell carcinoma (cSCC) and melanoma. cSCC is caused by altered growth factor signaling induced by chemical carcinogens, ultraviolet light (UV) exposure, and infections with papillomaviruses (PVs). One of the few options for preventing cSCC in high-risk patients is oral retinoids. While much is understood about retinoid treatments and metabolism in mouse models of chemically and UV exposure induced cSCC, little is known about the role of retinoids in PV-induced cSCC. To better understand how retinoid metabolism is altered in cSCC, we examined the expression of this pathway in the newly discovered mouse papillomavirus (MmuPV1), which produces trichoblastomas in dorsal skin but not cSCC. We found significant increases in a rate-limiting enzyme involved in retinoic acid synthesis and retinoic acid binding proteins, suggestive of increased RA synthesis, in MmuPV1-induced tumors in B6.Cg-Foxn1(nu)/J mice. Similar increases in these proteins were seen after acute UVB exposure in Crl:SKH1-Hr(hr) mice and in regressing pre-cancerous lesions in a chemically-induced mouse model, suggesting a common mechanism in limiting the progression of papillomas to full blown cSCC.

Identification of biomarkers regulated by rexinoids (LGD1069, LG100268 and Ro25-7386) in human breast cells using Affymetrix microarray

Retinoids possess anti-proliferative properties, which suggests that they possess chemopreventive and therapeutic potential against cancer. In the current study, genes modulated by rexinoids (retinoid X receptor (RXR)-pan agonists, LGD1069 and LG100268; and the RXRα agonist, Ro25-7386) were identified using an Affymetrix microarray in normal and malignant breast cells. It was observed that LGD1069, LG100268 and Ro25-7386 suppressed the growth of breast cells. Secondly, several rexinoid-regulated genes were identified, which are involved in cell death, cell growth/maintenance, signal transduction and response to stimulus. These genes may be associated with the growth-suppressive activity of rexinoids. Therefore, the identified genes may serve as biomarkers and novel molecular targets for the prevention and treatment of breast cancer.

Retinoic acid receptors: from molecular mechanisms to cancer therapy

Retinoic acid (RA), the major bioactive metabolite of retinol or vitamin A, induces a spectrum of pleiotropic effects in cell growth and differentiation that are relevant for embryonic development and adult physiology. The RA activity is mediated primarily by members of the retinoic acid receptor (RAR) subfamily, namely RARα, RARβ and RARγ, which belong to the nuclear receptor (NR) superfamily of transcription factors. RARs form heterodimers with members of the retinoid X receptor (RXR) subfamily and act as ligand-regulated transcription factors through binding specific RA response elements (RAREs) located in target genes promoters. RARs also have non-genomic effects and activate kinase signaling pathways, which fine-tune the transcription of the RA target genes. The disruption of RA signaling pathways is thought to underlie the etiology of a number of hematological and non-hematological malignancies, including leukemias, skin cancer, head/neck cancer, lung cancer, breast cancer, ovarian cancer, prostate cancer, renal cell carcinoma, pancreatic cancer, liver cancer, glioblastoma and neuroblastoma. Of note, RA and its derivatives (retinoids) are employed as potential chemotherapeutic or chemopreventive agents because of their differentiation, anti-proliferative, pro-apoptotic, and anti-oxidant effects. In humans, retinoids reverse premalignant epithelial lesions, induce the differentiation of myeloid normal and leukemic cells, and prevent lung, liver, and breast cancer. Here, we provide an overview of the biochemical and molecular mechanisms that regulate the RA and retinoid signaling pathways. Moreover, mechanisms through which deregulation of RA signaling pathways ultimately impact on cancer are examined. Finally, the therapeutic effects of retinoids are reported.

Addition of all-trans-retinoic acid to omeprazole and sucralfate therapy improves the prognosis of gastric dysplasia

OBJECTIVE

To investigate the efficacy of all-trans retinoic acid (ATRA) in human gastric dysplasia.

METHODS

In this double-blind study, patients with precancerous gastric dysplasia with or without intestinal metaplasia (IM) received either conventional treatment consisting of omeprazole and sucralfate (control group) or conventional treatment plus ATRA. Gastric mucosal biopsies were performed before and after drug treatment and were analysed histologically; expression of retinoblastoma (Rb) protein and HER2 protein in gastric mucosa were measured using immunohistochemistry.

RESULTS

A total of 122 patients were included in the study, 63 in the ATRA group and 59 in the control group. In the ATRA group, dysplasia was attenuated in 43 out of 63 patients (68%) compared with 22 out of 59 patients (37%) in the control group; however, IM was not affected by treatment in either group. ATRA treatment was associated with significantly increased Rb expression and decreased HER2 expression in gastric mucosa.

CONCLUSIONS

The use of conventional therapy plus ATRA for gastric dysplasia was associated with improved efficacy compared with conventional therapy alone. It was also accompanied by increased Rb expression and decreased HER2 expression in gastric mucosa. The addition of ATRA to conventional therapy for gastritis may improve the prognosis of gastric dysplasia.

High-throughput screen of natural product libraries for hsp90 inhibitors

Hsp90 has become the target of intensive investigation, as inhibition of its function has the ability to simultaneously incapacitate proteins that function in pathways that represent the six hallmarks of cancer. While a number of Hsp90 inhibitors have made it into clinical trials, a number of short-comings have been noted, such that the search continues for novel Hsp90 inhibitors with superior pharmacological properties. To identify new potential Hsp90 inhibitors, we have utilized a high-throughput assay based on measuring Hsp90-dependent refolding of thermally denatured luciferase to screen natural compound libraries. Over 4,000 compounds were screen with over 100 hits. Data mining of the literature indicated that 51 compounds had physiological effects that Hsp90 inhibitors also exhibit, and/or the ability to downregulate the expression levels of Hsp90-dependent proteins. Of these 51 compounds, seven were previously characterized as Hsp90 inhibitors. Four compounds, anthothecol, garcinol, piplartine, and rottlerin, were further characterized, and the ability of these compounds to inhibit the refolding of luciferase, and reduce the rate of growth of MCF7 breast cancer cells, correlated with their ability to suppress the Hsp90-dependent maturation of the heme-regulated eIF2α kinase, and deplete cultured cells of Hsp90-dependent client proteins. Thus, this screen has identified an additional 44 compounds with known beneficial pharmacological properties, but with unknown mechanisms of action as possible new inhibitors of the Hsp90 chaperone machine.

Targeting of histone deacetylases to reactivate tumour suppressor genes and its therapeutic potential in a human cervical cancer xenograft model

Aberrant histone acetylation plays an essential role in the neoplastic process via the epigenetic silencing of tumour suppressor genes (TSGs); therefore, the inhibition of histone deacetylases (HDAC) has become a promising target in cancer therapeutics. To investigate the correlation of histone acetylation with clinicopathological features and TSG expression, we examined the expression of acetylated H3 (AcH3), RARβ2, E-cadherin, and β-catenin by immunohistochemistry in 65 cervical squamous cell carcinoma patients. The results revealed that the absence of AcH3 was directly associated with poor histological differentiation and nodal metastasis as well as reduced/negative expression of RARβ2, E-cadherin, and β-catenin in clinical tumour samples. We further demonstrated that the clinically available HDAC inhibitors valproic acid (VPA) and suberoylanilide hydroxamic acid (SAHA), in combination with all-trans retinoic acid (ATRA), can overcome the epigenetic barriers to transcription of RARβ2 in human cervical cancer cells. Chromatin immunoprecipitation analysis showed that the combination treatment increased the enrichment of acetylated histone in the RARβ2-RARE promoter region. In view of these findings, we evaluated the antitumor effects induced by combined VPA and ATRA treatment in a xenograft model implanted with poorly differentiated human squamous cell carcinoma. Notably, VPA restored RARβ2 expression via epigenetic modulation. Additive antitumour effects were produced in tumour xenografts by combining VPA with ATRA treatment. Mechanistically, the combination treatment reactivated the expression of TSGs RARβ2, E-cadherin, P21 (CIP1) , and P53 and reduced the level of p-Stat3. Sequentially, upregulation of involucrin and loricrin, which indicate terminal differentiation, strongly contributed to tumour growth inhibition along with partial apoptosis. In conclusion, targeted therapy with HDAC inhibitors and RARβ2 agonists may represent a novel therapeutic approach for patients with cervical squamous cell carcinoma.

[Off-label use of alitretinoin]

Oral alitretinoin (9-cis retinoic acid) is an endogenous retinoid related to vitamin A. Studies have shown that oral alitretinoin is effective and well-tolerated in the treatment of severe chronic hand eczema, so that it is approved for this indication. This review summarizes new studies and clinical experience on the off-label use of alitretinoin.

Enhancement of all-trans retinoic acid-induced differentiation by pH-sensitive nanoparticles for solid tumor cells

Cancer differentiation therapy is an attractive concept and has been clinically used to treat leukemia. However, it is limited to date for solid tumors. In this study, the pH-sensitive nanoparticles based on poly(amidoamine) (PAMAM) dendrimers are synthesized by coupling 3,4,5,6-tetrahydrophthalic anhydride with the first generation PAMAM. The modified dendrimers can self-assemble in aqueous solution to form nanoparticles with a diameter of 125-435 nm. The nanoparticles are relatively stable at physiological pH (pH 7.4) but dissociated in acidic environments (pH 5.0 or 6.0). The present studies show that the proliferation inhibition and albumin secretion of hepatoma carcinoma cells are enhanced with all-trans retinoic acid (ATRA) encapsulated in the nanoparticles. The enhancement of induced differentiation is due to the high internalization of ATRA in the cells by the nanoparticles. These experimental results demonstrate that pH-sensitive nanoparticles may be efficient for improving the differentiation therapy for solid tumor.

A disease-drug-phenotype matrix inferred by walking on a functional domain network

Protein domains are classified as units of structure, evolution and function, and thus form the molecular backbone of biosphere. Although functional networks at the protein level have been reported to be of value in predicting diseases (phenotypes or drugs), they have not previously been applied at the sub-protein resolution (protein domain in this case). We herein introduce a domain network with a functional perspective. This network has nodes consisting of protein domains (at the superfamily/evolutionary level), with edges weighted by the semantic similarity according to domain-centric Gene Ontology (dcGO) annotations, which henceforth we call "dcGOnet". By globally exploring this network via a random walk, we demonstrate its predictive value on disease, drug, or phenotype-related ontologies. On cross-validation recovering ontology labels for domains, we achieve an overall area under the ROC curve of 89.0% for drugs, 87.3% for diseases, 87.6% for human phenotypes and 88.2% for mouse phenotypes. We show that the performance using global information from this network is significantly better than using local information, and also illustrate that the better performance is not sensitive to network size, or the choice of algorithm parameters, and is universal to different ontologies. Based on the dcGOnet and its global properties, we further develop an approach to build a disease-drug-phenotype matrix. The predicted interconnections are statistically supported using a novel randomization procedure, and are also empirically supported by inspection for biological relevance. Most of the high-ranking predictions recover connections that are well known, but others uncover connections that have only suggestive or obscure support in the literature; we show that these are missed by simpler methods, in particular for drug-disease connections. The value of this work is threefold: we describe a general methodology and make the software available, we provide the functional domain network itself, and the ranked drug-disease-phenotype matrix provides rich targets for investigation. All three can be found at .

Retinoid receptors in gastric cancer: expression and influence on prognosis

BACKGROUND

Gastric cancer is frequently lethal despite aggressive multimodal therapies, and new treatment approaches are therefore needed. Retinoids are potential candidate drugs: they prevent cell differentiation, proliferation and malignant transformation in gastric cancer cell lines. They interact with nuclear retinoid receptors (the retinoic acid receptors [RARs] and retinoid X receptors [RXRs]), which function as transcription factors, each with three subclasses, α, β and γ. At present, little is known about retinoid expression and influence on prognosis in gastric cancers.

PATIENTS AND METHODS

We retrospectively analyzed the expression of the subtypes RARα, RARβ, RARγ, RXRα, RXRβ, RXRγ by immunohistochemistry in 147 gastric cancers and 51 normal gastric epithelium tissues for whom clinical follow-up data were available and correlated the results with clinical characteristics. In addition, we quantified the expression of retinoid receptor mRNA using real- time PCR (RT-PCR) in another 6 gastric adenocarcinoma and 3 normal gastric tissues. From 2008 to 2010, 80 patients with gastric cancers were enrolled onto therapy with all-trans-retinoic acid (ATRA).

RESULTS

RARα, RARβ, RARγ and RXRγ positively correlated with each other (p<0.001) and demonstrated significantly lower levels in the carcinoma tissue sections (p<0.01), with lower RARβ, RARγ and RXRα expression significantly related to advanced stages (p<=0.01). Tumors with poor histopathologic grade had lower levels of RARα and RARβ in different histological types of gastric carcinoma (p<0.01). Patients whose tumors exhibited low levels of RARa expression had significantly lower overall survival compared with patients who had higher expression levels of this receptor (p<0.001, HR=0.42, 95.0% CI 0.24-0.73), and patients undergoing ATRA treatment had significantly longer median survival times (p=0.007, HR=0.41, 95.0% CI 0.21-0.80).

CONCLUSIONS

Retinoic acid receptors are frequently expressed in epithelial gastric cancer with a decreased tendency of expression and RARa may be an indicator of a positive prognosis. This study provides a molecular basis for the therapeutic use of retinoids against gastric cancer.

Enzymes of the AKR1B and AKR1C Subfamilies and Uterine Diseases

Endometrial and cervical cancers, uterine myoma, and endometriosis are very common uterine diseases. Worldwide, more than 800,000 women are affected annually by gynecological cancers, as a result of which, more than 360,000 die. During their reproductive age, about 70% of women develop uterine myomas and 10-15% suffer from endometriosis. Uterine diseases are associated with aberrant inflammatory responses and concomitant increased production of prostaglandins (PG). They are also related to decreased differentiation, due to low levels of protective progesterone and retinoic acid, and to enhanced proliferation, due to high local concentrations of estrogens. The pathogenesis of these diseases can thus be attributed to disturbed PG, estrogen, and retinoid metabolism and actions. Five human members of the aldo-keto reductase 1B (AKR1B) and 1C (AKR1C) superfamilies, i.e., AKR1B1, AKR1B10, AKR1C1, AKR1C2, and AKR1C3, have roles in these processes and can thus be implicated in uterine diseases. AKR1B1 and AKR1C3 catalyze the formation of PGF2α, which stimulates cell proliferation. AKR1C3 converts PGD2 to 9α,11β-PGF2, and thus counteracts the formation of 15-deoxy-PGJ2, which can activate pro-apoptotic peroxisome-proliferator-activated receptor γ. AKR1B10 catalyzes the reduction of retinal to retinol, and thus lessens the formation of retinoic acid, with potential pro-differentiating actions. The AKR1C1-AKR1C3 enzymes also act as 17-keto- and 20-ketosteroid reductases to varying extents, and are implicated in increased estradiol and decreased progesterone levels. This review comprises an introduction to uterine diseases and AKR1B and AKR1C enzymes, followed by an overview of the current literature on the AKR1B and AKR1C expression in the uterus and in uterine diseases. The potential implications of the AKR1B and AKR1C enzymes in the pathophysiologies are then discussed, followed by conclusions and future perspectives.

Tributyltin-induced imposex in marine gastropods involves tissue-specific modulation of the retinoid X receptor

Despite the large number of studies on the phenomenon of imposex, the mechanism underlying the abnormal growth of male sexual characters onto females in numerous gastropod species is yet to be fully elucidated. Although several hypotheses have been raised over the years, a convincing body of evidence indicates that tributyltin-induced imposex involves the abnormal modulation of the retinoid X receptor (RXR). Here, we investigate the RXR gene transcription at different timings and tissues upon exposure to environmentally relevant concentrations of tributyltin (TBT) (100 ng Sn/L TBT) in both genders of the imposex susceptible gastropod Nucella lapillus. RXR gene transcription was determined at two time-points (i.e., before and after imposex initiation) by quantitative Real Time PCR in potential target tissues: the central nervous system (CNS), penis/penis forming area (PFA), gonads and digestive gland. TBT-exposure altered transcription of RXR gene in a tissue and sex specific manner. In the CNS, a significant down-regulation was observed in females both before and after imposex initiation (P≤0.01 and P≤0.05, respectively). A similar trend was observed in male CNS at the first time-point, although differences between control and the TBT-exposed group were just above significance (P=0.059). The penis/PFA showed no differences in transcription of RXR gene between control and TBT exposed female snails before imposex induction, or before and after imposex initiation for males. However, male penis showed higher transcription of RXR gene in comparison to the PFA of females. After imposex has been induced, a significant (P≤0.001) increase in transcription of RXR gene was observed in penis of females with vas deference sequence index (VDS) levels of 3-4 in comparison with the PFA of both control and imposex females with VDS 1-2. At advanced stages of imposex, females displayed RXR transcription patterns in penis identical to those of males, which points to a functional role of RXR in the penis of both genders. In the other tissues, gonads and digestive gland, RXR gene transcription was not affected by TBT, at any of the analysed time-points. These patterns of RXR gene transcription upon TBT exposure highlight the pivotal involvement of the CNS in the mechanism of imposex induction. We integrate the results in a conceptual model, and discuss the central role of RXR and the retinoic acid signalling pathways in imposex and male genitalia formation in gastropods.

No association between endogenous retinoic acid and human papillomavirus clearance or incident cervical lesions in Brazilian women

Although oncogenic human papillomavirus (HPV) infections have been established as the necessary cause of cervical cancer, most HPV infections are transient and rarely progress to squamous cervical lesions. The activity of HPV is tightly associated with epithelial cell differentiation; therefore, regulators of differentiation, such as retinoic acid (RA), have been considered targets for the prevention of HPV-associated squamous intraepithelial lesion (SIL) development. The purpose of this study was to determine the association between circulating RA and early events in cervical carcinogenesis, specifically type-specific HPV clearance and SIL detection. Archived blood samples from 643 women participating in the Ludwig-McGill Cohort in São Paulo, Brazil, were analyzed by high-pressure liquid chromatography for three RA isomers (all-trans, 13-cis, and 9-cis-RA). A type-specific HPV clearance event was defined as two consecutive visits negative for an HPV type during follow-up for 364 HPV-positive women. Among the 643 women in this analysis, 78 were diagnosed with incident SIL. The probability of clearing an oncogenic HPV infection was not significantly different across RA isomer quartiles. There was a suggestion that increasing all-trans-RA increased the rate of nononcogenic HPV clearance (P-trend = 0.05). There was no association observed between serum RA levels and incident SIL. Our results suggest that elevated circulating RA isomer levels do not increase the rate of HPV clearance or reduce the risk of incident SIL. The role of RA in the inhibition of HPV-induced carcinogenesis, as shown in vitro, lacks confirmatory evidence within epidemiologic studies among women.

Enhancement of ATRA-induced differentiation of neuroblastoma cells with LOX/COX inhibitors: an expression profiling study

BACKGROUND

We performed expression profiling of two neuroblastoma cell lines, SK-N-BE(2) and SH-SY5Y, after combined treatment with all-trans retinoic acid (ATRA) and inhibitors of lipoxygenases (LOX) and cyclooxygenases (COX). This study is a continuation of our previous work confirming the possibility of enhancing ATRA-induced cell differentiation in these cell lines by the application of LOX/COX inhibitors and brings more detailed information concerning the mechanisms of the enhancement of ATRA-induced differentiation of neuroblastoma cells.

METHODS

Caffeic acid, as an inhibitor of 5-lipoxygenase, and celecoxib, as an inhibitor on cyclooxygenase-2, were used in this study. Expression profiling was performed using Human Cancer Oligo GEArray membranes that cover 440 cancer-related genes.

RESULTS

Cluster analyses of the changes in gene expression showed the concentration-dependent increase in genes known to be involved in the process of retinoid-induced neuronal differentiation, especially in cytoskeleton remodeling. These changes were detected in both cell lines, and they were independent of the type of specific inhibitors, suggesting a common mechanism of ATRA-induced differentiation enhancement. Furthermore, we also found overexpression of some genes in the same cell line (SK-N-BE(2) or SH-SY5Y) after combined treatment with both ATRA and CA, or ATRA and CX. Finally, we also detected that gene expression was changed after treatment with the same inhibitor (CA or CX) in combination with ATRA in both cell lines.

CONCLUSIONS

Obtained results confirmed our initial hypothesis of the common mechanism of enhancement in ATRA-induced cell differentiation via inhibition of arachidonic acid metabolic pathway.

Combined low doses of PPARgamma and RXR ligands trigger an intrinsic apoptotic pathway in human breast cancer cells

Ligand activation of peroxisome proliferator-activated receptor (PPAR)gamma and retinoid X receptor (RXR) induces antitumor effects in cancer. We evaluated the ability of combined treatment with nanomolar levels of the PPARgamma ligand rosiglitazone (BRL) and the RXR ligand 9-cis-retinoic acid (9RA) to promote antiproliferative effects in breast cancer cells. BRL and 9RA in combination strongly inhibit of cell viability in MCF-7, MCF-7TR1, SKBR-3, and T-47D breast cancer cells, whereas MCF-10 normal breast epithelial cells are unaffected. In MCF-7 cells, combined treatment with BRL and 9RA up-regulated mRNA and protein levels of both the tumor suppressor p53 and its effector p21(WAF1/Cip1). Functional experiments indicate that the nuclear factor-kappaB site in the p53 promoter is required for the transcriptional response to BRL plus 9RA. We observed that the intrinsic apoptotic pathway in MCF-7 cells displays an ordinated sequence of events, including disruption of mitochondrial membrane potential, release of cytochrome c, strong caspase 9 activation, and, finally, DNA fragmentation. An expression vector for p53 antisense abrogated the biological effect of both ligands, which implicates involvement of p53 in PPARgamma/RXR-dependent activity in all of the human breast malignant cell lines tested. Taken together, our results suggest that multidrug regimens including a combination of PPARgamma and RXR ligands may provide a therapeutic advantage in breast cancer treatment.

Studies on Multifunctional Effect of All-Trans Retinoic Acid (ATRA) on Matrix Metalloproteinase-2 (MMP-2) and Its Regulatory Molecules in Human Breast Cancer Cells (MCF-7)

Background. Vitamin A derivative all-trans retinoic acid (ATRA) is considered as a potent chemotherapeutic drug for its capability of regulating cell growth and differentiation. We studied the effect of ATRA on MMP-2 in MCF-7, human breast cancer cells, and the probable signaling pathways which are affected by ATRA on regulating pro-MMP-2 activity and expression. Methods. Gelatin zymography, RT-PCR, ELISA, Western blot, Immunoprecipitation, and Cell adhesion assay are used. Results. Gelatin zymography showed that ATRA caused a dose-dependent inhibition of pro-MMP-2 activity. ATRA treatment downregulates the expression of MT1-MMP, EMMPRIN, FAK, NF-kB, and p-ERK. However, expression of E-cadherin, RAR, and CRABP increased upon ATRA treatment. Binding of cells to extra cellular matrix (ECM) protein fibronectin reduced significantly after ATRA treatment. Conclusions. The experimental findings clearly showed the inhibition of MMP-2 activity upon ATRA treatment. This inhibitory effect of ATRA on MMP-2 activity in human breast cancer cells (MCF-7) may result due to its inhibitory effect on MT1-MMP, EMMPRIN, and upregulation of TIMP-2. This study is focused on the effect of ATRA on MMP, MMP-integrin-E-cadherin interrelationship, and also the effect of the drug on different signaling molecules which may involve in the progression of malignant tumor development.

Modulation of plasma all-trans retinoic acid concentrations by the consumption of carotenoid-rich vegetables

OBJECTIVE

A human intervention trial was conducted to determine the effects of consumption of carotenoid-rich vegetables on levels of retinol (ROL) and the active vitamin A metabolite all-trans retinoic acid (ATRA).

METHODS

The study was divided into four periods, each lasting 2 wk: weeks 1-2, a low carotenoid period; weeks 3-4, daily consumption of 330 mL of tomato juice; weeks 5-6, 330 mL of carrot juice daily; and weeks 7-8, 10 g of dried spinach powder daily. ROL and ATRA concentrations were measured after each 2-wk study period.

RESULTS AND CONCLUSION

This study shows that consumption of carrot juice containing high concentrations of the pro-vitamin A carotenoid beta-carotene results in slightly, non-significantly increased plasma ROL concentrations and strong, significantly increased (almost double, from 1.2 +/- 0.3 to 2.0 +/- 0.31 ng/mL) plasma concentrations of ATRA, whereas consumption of tomato juice and spinach powder results in no significant alteration in concentrations of plasma ROL and ATRA.

Chemotherapeutic/chemopreventive role of retinoids in chemically induced skin carcinogenesis in albino mice

OBJECTIVE

To determine the chemotherapeutic effect of retinoids on albino mouse skin.

METHODS

Eighty albino mice were selected for this study and were divided into four groups (A-D, 20 mice in each group). 7,12-Dimethylbenz(a)anthracene (DMBA) and tetradecanoylphorbal-13-acetate (TPA) were given for 15 weeks to produce tumors. Retinoids were given topically and orally after the development of tumors for the following 15 weeks.

RESULTS

Of the 80 mice, 69 (86.25%) developed different types of lesion and 11 (13.75%) remained lesion free. Of the 69 mice that developed lesions, 50 (62.50%) developed benign lesions and 19 (23.75%) developed malignant lesions. In all groups of mice, treatment with retinoids was effective against all benign lesions and the early stages of carcinogenesis of the skin. The chemotherapeutic effect against malignant tumors was not satisfactory.

CONCLUSION

This study demonstrates that retinoids are effective as chemopreventive agents in premalignant lesions of the skin, but have a very weak chemotherapeutic role in malignant neoplasms. If retinoids are given at an early stage, they can cause regression of premalignant lesions of the skin. They are best administered both orally and parenterally. These agents should be recommended as they reduce the potential effects of carcinogenesis.

Retinol activates tyrosine hydroxylase acutely by increasing the phosphorylation of serine40 and then serine31 in bovine adrenal chromaffin cells

Tyrosine hydroxylase is the rate-limiting enzyme in the biosynthesis of the catecholamines. It has been reported that retinol (vitamin A) modulates tyrosine hydroxylase activity by increasing its expression through the activation of the nuclear retinoid receptors. In this study, we observed that retinol also leads to an acute activation of tyrosine hydroxylase in bovine adrenal chromaffin cells and this was shown to occur via two distinct non-genomic mechanisms. In the first mechanism, retinol induced an influx in extracellular calcium, activation of protein kinase C and serine40 phosphorylation, leading to tyrosine hydroxylase activation within 15 min. This effect then declined over time. The retinol-induced rise in intracellular calcium then led to a second slower mechanism; this involved an increase in reactive oxygen species, activation of extracellular signal-regulated kinase 1/2 and serine31 phosphorylation and the maintenance of tyrosine hydroxylase activation for up to 2 h. No effects were observed with retinoic acid. These results show that retinol activates tyrosine hydroxylase via two sequential non-genomic mechanisms, which have not previously been characterized. These mechanisms are likely to operate in vivo to facilitate the stress response, especially when vitamin supplements are taken or when retinol is used as a therapeutic agent.

Uterine leiomyomas express a molecular pattern that lowers retinoic acid exposure

OBJECTIVE

To analyze expression of the retinoic acid signaling pathway genes that are involved in retinol metabolism, transport, transcriptional activation, and transcriptional products in spontaneous human leiomyomas.

DESIGN

Laboratory study of human leiomyoma and patient-matched myometrial tissue.

PATIENT(S)

Eight women undergoing hysterectomy for symptomatic leiomyomas.

INTERVENTION(S)

Confirmation of an altered retinoic acid pathway analyzed by microarray, real time reverse transcription-polymerase chain reaction, Western blot, immunohistochemistry, and high-performance liquid chromatography (HPLC).

MAIN OUTCOME MEASURE(S)

Gene and protein expression.

RESULT(S)

Regardless of patient demographics and leiomyoma location and size, we found decreased expression of the major genes involved in retinoic acid pathway including alcohol dehydrogenase-1 (-3.97- +/- 0.03-fold), aldehyde dehydrogenase-1 (-3.1- +/- 0.07-fold), cellular retinol binding protein-1 (-2.62- +/- 0.04-fold), and cellular retinoic acid binding protein-1 (-2.42- +/- 0.20-fold). Cytochrome P450 (CYP 26A1), which is responsible for retinoic acid metabolism, was highly up-regulated in leiomyomas (+5.4- +/- 0.53-fold). Nuclear receptors demonstrated a complex pattern of under-expression (RARalpha, RARbeta, RXRalpha, RXRgamma) and over-expression (RARgamma, RXRbeta) at both the mRNA and protein level. Differences in protein amounts were confirmed by Western blot. Finally, a reduced amount of cellular ATRA and 9-cis retinoic acid was confirmed by HPLC in leiomyomas compared with myometrial tissues.

CONCLUSION(S)

Molecular alterations in the retinoic acid pathway of leiomyomata result in a decrease in retinoic acid exposure.

The discovery of new coding alleles of human CYP26A1 that are potentially defective in the metabolism of all-trans retinoic acid and their assessment in a recombinant cDNA expression system

OBJECTIVES

Retinoic acid (RA) is a critical regulator of gene expression during embryonic development and in the maintenance of adult epithelial tissues. This study was undertaken to identify genetic polymorphisms of CYP26A1 which might affect these processes. We sequenced CYP26A1 in racially diverse individuals and assessed the metabolism of retinoic acid by newly identified coding alleles of CYP26A1 in a recombinant system.

METHODS

CYP26A1 was sequenced in 24 Caucasians, 24 African-Americans, 24 Asians, and 20 individuals of unknown racial origin. cDNA constructs for wild-type and coding alleles of CYP26A1 were constructed in a pcDNA3.1 expression vector and expressed in Cos-1 cells. A FLAG tag at the C-terminal end of the cDNA was used to quantitate the recombinant CYP26A1 proteins.

RESULTS

A total of 13 single nucleotide polymorphisms (SNPs) were identified in CYP26A1. Three SNPs produced coding changes: R173S, F186L, and C358R. These alleles were termed as CYP26A1*2, CYP26A1*3, and CYP26A1*4, respectively, by the Human Cytochrome P450 (CYP) Allele Nomenclature Committee at http://www.cypalleles.ki.se/. Wild type CYP26A1 protein metabolized all-trans-retinoic acid (at-RA) to 4-oxo-RA, 4-OH-RA as well as water-soluble metabolites. CYP26A1.3 (F186L) and CYP26A1.4 (C358R) allelic proteins exhibited significantly lower metabolism (40-80%) of at-RA than wild-type CYP26A1.1 protein.

CONCLUSION

This is the first study to identify coding alleles of CYP26A1. Two coding alleles, CYP26A1*3 and CYP26A1*4, are predicted to be defective based on the metabolism of at-RA by the recombinant proteins. These studies suggest the need for future clinical studies of polymorphisms of CYP26A1 in embryonic development.

Involvement of apoptotic cell death and cell cycle perturbation in retinoic acid-induced cleft palate in mice

Retinoic acid (RA), a metabolite of vitamin A, plays a key role in a variety of biological processes and is essential for normal embryonic development. On the other hand, exogenous RA could cause cleft palate in offspring when it is given to pregnant animals at either the early or late phases of palatogenesis, but the pathogenetic mechanism of cleft palate caused by excess RA remains not fully elucidated. The aim of the present study was to investigate the effects of excess of RA on early palatogenesis in mouse fetuses and analyze the teratogenic mechanism, especially at the stage prior to palatal shelf elevation. We gave all-trans RA (100 mg/kg) orally to E11.5 ICR pregnant mice and observed the changes occurring in the palatal shelves of their fetuses. It was found that apoptotic cell death increased not only in the epithelium of the palatal shelves but also in the tongue primordium, which might affect tongue withdrawal movement during palatogenesis and impair the horizontal elevation of palatal shelves. In addition, RA was found to prevent the G(1)/S progression of palatal mesenchymal cells through upregulation of p21(Cip1), leading to Rb hypophospholylation. Thus, RA appears to cause G(1) arrest in palatal mesenchymal cells in a similar manner as in various cancer and embryonic cells. It is likely that apoptotic cell death and cell cycle disruption are involved in cleft palate formation induced by RA.

Down-regulation of retinol binding protein 5 is associated with aggressive tumor features in hepatocellular carcinoma

PURPOSE

Acyclic retinoid (ACR) has been shown to be a promising chemopreventive agent for hepatocellular carcinoma (HCC) after curative resection. The effects of retinoid are mediated by retinol-binding proteins (RBPs) through regulating cell proliferation and differentiation.

PATIENTS AND METHODS

This study investigated the clinical significance of RBP5 in HCC. RBP5 mRNA level was examined by real-time quantitative PCR on 52 matched tumor and adjacent non-tumor liver tissues, and on ten normal livers. Expression of RBP5 protein was examined using Western blotting analysis and immunohistochemistry.

RESULTS

Down-regulation of RBP5 was found in HCC tissues at both mRNA and protein levels. Decreased RBP5 level was closely related to poor differentiation (P=0.02) and large tumor size (P=0.01). Low level of RPB5 was associated with poor overall survival (P=0.02), and was an independent prognostic factor for HCC.

CONCLUSIONS

Our study revealed that RBP5 down-regulation in HCC was associated with aggressive tumor features, suggesting an important role of RPB5 in HCC progression.

Inhibition of 13-cis retinoic acid-induced gene expression of homeobox B7 by thalidomide

Thalidomide and 13-cis retinoic acid (RA) show anticancer effects as sole agents or in combination with other drugs. However, induction of homeobox (HOX) gene expression by 13-cis RA may contribute to tumor progression thereby potentially limiting its efficacy. The purpose was to test if thalidomide can inhibit 13-cis RA-induced HOXB7 expression and whether thalidomide may enhance the antiproliferative effect of 13-cis RA in U343MG glioblastoma cells. Quantitative real-time PCR showed significant inhibition of 13-cis RA-induced HOXB7 expression by thalidomide with IC(50) approximately 0.1-0.2 microg/ml when given simultaneously with 13-cis RA but not when administered 18 h later (p < 0.0001). 13-cis RA alone inhibited proliferation and colony formation in a concentration-dependent manner whereas growth inhibition by thalidomide alone at 5-100 microg/ml was constant at 80-90% of controls. At 10% serum concentration, growth inhibition by a combination of the 2 drugs was additive but at 1% serum, growth inhibition was synergistic. It is concluded that thalidomide inhibits the RA-induced HOXB7 expression in glioblastoma cells and that 13-cis RA/thalidomide combinations can in principle enhance cytotoxicity. The improved cell kill induced by thalidomide is attributed to downregulation of growth stimulatory factors induced by 13-cis RA. Implications for the modus operandi of thalidomide in embryogenesis are noted.

An armamentarium of wart treatments

Patients and clinicians experience the frustration of cutaneous viral warts caused by infection with the human papilloma virus (HPV).Warts appear in various forms on different sites of the body and include common warts (verruca vulgaris), plane or flat warts, myrmecia, plantar warts, coalesced mosaic warts, filiform warts, periungual warts, anogenital warts (venereal or condyloma acuminata), oral warts and respiratory papillomas. Cervical infection with HPV is now known to cause cervical cancer if untreated. A review of the medical literature reveals a huge armamentarium of wart monotherapies and combination therapies. Official evidence-based guidelines exist for the treatment of warts, but very few of the reported treatments have been tested by rigorous blinded, randomized controlled trials.Therefore, official recommendations do not often include treatments with reportedly high success rates, but they should not be ignored when considering treatment options. It is the purpose of this review to provide a comprehensive overview of the wart treatment literature to expand awareness of the options available to practitioners faced with patients presenting with problematic warts.

Apoptotic and anti-proliferative effects of all-trans retinoic acid. Adenine nucleotide translocase sensitizes HeLa cells to all-trans retinoic acid

We examined the apoptotic and anti-proliferative effects of all-trans retinoic acid (atRA) in HeLa cells. Our results demonstrated that HeLa cells were more sensitive to the anti-proliferative effects of atRA than to its apoptotic effects. Furthermore, we demonstrated that caspase inhibition attenuates cell death but does not alter the atRA-dependent reduction in cell proliferation, which suggests that atRA-induced apoptosis is independent of the arrest in cell proliferation. To check whether ANT proteins mediated these atRA effects, we transiently transfected cells with expression vectors encoding for individual ANT (adenine nucleotide translocase 1-3). Our results revealed that ANT1 and ANT3 over-expressing HeLa cells increased their atRA sensitivity. Thus, our results not only demonstrate the different functional activities of ANT isoforms, but also contribute to a better understanding of the properties of atRA as an anti-tumoral agent used in cancer therapy.