Recent advances in the use of vitamin A (retinoids) in the prevention and treatment of cancer

Supplement Use and Increased Risks of Cancer: Unveiling the Other Side of the Coin

There is a rising trend in the consumption of dietary supplements, especially among adults, with the purpose of improving health. While marketing campaigns tout the potential health benefits of using dietary supplements, it is critical to evaluate the potential harmful effects associated with these supplements as well. The majority of the scarce research on the potential harmful effects of vitamins focuses on the acute or chronic toxicities associated with the use of dietary supplements. Quality research is still required to further investigate the risks of long-term use of dietary supplements, especially the risk of developing cancers. The present review concentrates on studies that have investigated the association between the risk of developing cancers and associated mortality with the risk of dietary supplements. Such an association has been reported for several vitamins, minerals, and other dietary supplements. Even though several of these studies come with their own shortcomings and critics, they must draw attention to further investigate long-term adverse effects of dietary supplements and advise consumers and healthcare providers to ponder the extensive use of dietary supplements.

Emerging Roles of Aldehyde Dehydrogenase Isoforms in Anti-cancer Therapy Resistance

Aldehyde dehydrogenases (ALDHs) are a family of detoxifying enzymes often upregulated in cancer cells and associated with therapeutic resistance. In humans, the ALDH family comprises 19 isoenzymes active in the majority of mammalian tissues. Each ALDH isoform has a specific differential expression pattern and most of them have individual functional roles in cancer. ALDHs are overexpressed in subpopulations of cancer cells with stem-like features, where they are involved in several processes including cellular proliferation, differentiation, detoxification and survival, participating in lipids and amino acid metabolism and retinoic acid synthesis. In particular, ALDH enzymes protect cancer cells by metabolizing toxic aldehydes in less reactive and more soluble carboxylic acids. High metabolic activity as well as conventional anticancer therapies contribute to aldehyde accumulation, leading to DNA double strand breaks (DSB) through the generation of reactive oxygen species (ROS) and lipid peroxidation. ALDH overexpression is crucial not only for the survival of cancer stem cells but can also affect immune cells of the tumour microenvironment (TME). The reduction of ROS amount and the increase in retinoic acid signaling impairs immunogenic cell death (ICD) inducing the activation and stability of immunosuppressive regulatory T cells (Tregs). Dissecting the role of ALDH specific isoforms in the TME can open new scenarios in the cancer treatment. In this review, we summarize the current knowledge about the role of ALDH isoforms in solid tumors, in particular in association with therapy-resistance.

Dietary components and the risk of non-melanoma skin cancer: A systematic review of epidemiological studies

Non-melanoma skin cancer (NMSC) is the most common cancer among white-skinned people. The main environmental risk factor for all types of skin cancer is ultraviolet (UV) exposure to the sun. However, significant modifiable risk factors, such as diet, have been studied about NMSC risk. Several original studies have been conducted on the link between various dietary components and the risk of NMSC in the past decade, but have not been systematically reviewed. This review focuses on the potential impact of dietary components in the prevention of NMSC and evaluates the findings of epidemiologic evidence for dietary factors. We conducted a systematic search of three databases, including Scopus, ISI Web of Science, and PubMed, to identify relevant epidemiological studies published between 2000 and July 6, 2021. Finally, forty-three articles were included. Because of the inherent limitations of epidemiological studies, no definitive conclusions can be drawn; however, the links between folate, citrus, caffeine, and alcohol with BCC are notable; thus, high dietary folate intake, as well as citrus and alcohol consumption, are associated with an increased risk of basal cell carcinoma (BCC), whereas caffeine is associated with a lower risk. More research is required to reach a definitive conclusion.

Nutritional Interventions for Patients with Melanoma: From Prevention to Therapy-An Update

Melanoma is an aggressive skin cancer, whose incidence rates have increased over the past few decades. Risk factors for melanoma are both intrinsic (genetic and familiar predisposition) and extrinsic (environment, including sun exposure, and lifestyle). The recent advent of targeted and immune-based therapies has revolutionized the treatment of melanoma, and research is focusing on strategies to optimize them. Obesity is an established risk factor for several cancer types, but its possible role in the etiology of melanoma is controversial. Body mass index, body surface area, and height have been related to the risk for cutaneous melanoma, although an 'obesity paradox' has been described too. Increasing evidence suggests the role of nutritional factors in the prevention and management of melanoma. Several studies have demonstrated the impact of dietary attitudes, specific foods, and nutrients both on the risk for melanoma and on the progression of the disease, via the effects on the oncological treatments. The aim of this narrative review was to summarize the main literature results regarding the preventive and therapeutic role of nutritional schemes, specific foods, and nutrients on melanoma incidence and progression.

An Updated Comprehensive Review on Vitamin A and Carotenoids in Breast Cancer: Mechanisms, Genetics, Assessment, Current Evidence, and Future Clinical Implications

Vitamin A and carotenoids are fat-soluble micronutrients that play important role as powerful antioxidants modulating oxidative stress and cancer development. Breast cancer is the most common malignancy in women. As the risk of breast cancer is dependent on various lifestyle factors such as dietary modifications, there is increasing interest surrounding the anti-cancerous properties of vitamin A and carotenoids. Despite the suggested protective roles of vitamin A and carotenoids in breast cancer development, their clinical application for the prevention and treatment of breast cancer is limited. In this narrative review, we discuss the roles of vitamin A and carotenoids along with the evaluation method of vitamin A status. We also exhibit the association of genetic variations involved in metabolism of vitamin A and carotenoids with cancers and other diseases. We demonstrate the epidemiological evidence for the relationship of vitamin A and carotenoids with breast cancer risk, their effects on cancer mechanism, and the recent updates in clinical practice of vitamin A or carotenoids as a potential therapeutic agent against breast cancer. This review provides insight into the preventive and therapeutic roles of vitamin A and carotenoids in breast cancer development and progression.

Boman B. Retinoids in Treatment of Colorectal Cancer

Retinoids are vitamin A metabolites best known for their role in embryonic development. Indeed, retinoid acid (RA) signaling plays a key role in regulating the development of the embryo body-plan by controlling embryonic stem cells (SCs). Retinoids function through their ability to induce cellular differentiation. Mutations in RA signaling pathway genes occur in most human cancers. The classic example is the chromosomal translocation involving RA receptor alpha in acute promyelocytic leukemia (APL). Because all-trans retinoic acid (ATRA) is a highly effective and often curative treatment for APL patients, determining if retinoids are efficacious for other cancer types is imperative. We review the current research on retinoids in colorectal cancer (CRC) and provide bioinformatics analyses of RA signaling. Our results show that most RA pathway genes are overexpressed and often mutated in CRC. Moreover, aberrant expression of many RA signaling proteins predicts decreased CRC patient survival. We also review aldehyde dehydrogenase (ALDH) expression in CRC because ALDH is a key enzyme in RA signaling, which regulates colonic SCs. Further investigation of RA signaling mechanisms that regulate colon SCs and how dysregulation contributes to the SC overpopulation that drives CRC growth should provide insight into strategies for designing new SC-targeted therapies for CRC.

Current Therapeutic Strategies of Xeroderma Pigmentosum

Xeroderma pigmentosum (XP) is an autosomal recessive genetic disease caused by a defect in the DNA repair system, exhibiting skin cancer on sun exposure. As it is an incurable disease, therapeutic strategies of this disease are critical. This review article takes an attempt to explore the current therapeutic advancements in XP. Different approaches including sun avoidance; surgical removal of cancerous lesions; laser and photodynamic therapy; use of retinoid, 5-fluorouracil, imiquimod, photolyase, and antioxidant; interferon therapy and gene therapy are chosen by doctors and patients to lessen the adverse effects of this disease. Among these options, sun avoidance, use of 5-fluorouracil and imiquimod, and interferon therapy are effective. However, some approaches including laser and photodynamic therapy, and the use of retinoids are effective against skin cancer having severe side effects. Furthermore, surgical removal of cancerous lesions and use of antioxidants are considered to be effective against this disease; however, efficacies of these are not experimentally determined. In addition, some approaches including oral vismodegib, immunotherapy, nicotinamide, acetohexamide, glimepiride-restricted diet are found to be effective to minimize the complications secondary to defects in the nucleotide excision repair (NER) system and also enhance the NER, which are under experimental level yet. Besides these, gene therapy, including the introduction of missing genes and genome edition, may be a promising approach to combat this disease, which is also not well established now. In the near future, these approaches may be effective tools to manage XP.

Therapeutic strategies and potential implications of silver nanoparticles in the management of skin cancer

Skin cancer (SC) is the most common carcinoma affecting 3 million people annually in the United States and millions of people worldwide. It is classified as melanoma SC (MSC) and non-melanoma SC (NMSC). NMSC represents approximately 80% of SC and includes squamous cell carcinoma and basal cell carcinoma. MSC, however, has a higher mortality rate than SC because of its ability to metastasize. SC is a major health problem in the United States with significant morbidity and mortality in the Caucasian population. Treatment options for SC include cryotherapy, excisional surgery, Mohs surgery, curettage and electrodessication, radiation therapy, photodynamic therapy, immunotherapy, and chemotherapy. Treatment is chosen based on the type of SC and the potential for side effects. Novel targeted therapies are being used with increased frequency for large tumors and for metastatic disease. A scoping literature search on PubMed, Google Scholar, and Cancer Registry websites revealed that traditional chemotherapeutic drugs have little effect against SC after the cancer has metastasized. Following an overview of SC biology, epidemiology, and treatment options, this review focuses on the mechanisms of advanced technologies that use silver nanoparticles in SC treatment regimens.

Radiation-induced curcumin release from curcumin–chitosan polymer films

The probability of human exposure to damaging radiation is increased in activities associated with long-term space flight, medical radiation therapies, and responses to nuclear accidents. However, the development of responsive countermeasures to combat radiation damage to biological tissue is lagging behind rates of human exposure. Herein, we report a radiation-responsive drug delivery system that releases doses of curcumin from a chitosan polymer/film in response to low level gamma radiation exposure. As a fibrous chitosan–curcumin polymer, 1 Gy gamma irradiation (¹³⁷Cs) released 5 ± 1% of conjugated curcumin, while 6 Gy exposure releases 98 ± 1% of conjugated curcumin. The same polymer was formed into a film through solvent casting. The films showed similar, albeit attenuated behavior in water (100% released) and isopropyl alcohol (32% released) with statistically significant drug release following 2 Gy irradiation. ATR FT-IR studies confirmed glycosidic bond cleavage in the chitosan–curcumin polymer in response to gamma radiation exposure. Similar behavior was noted upon exposure of the polymer to 20 cGy (1 GeV amu⁻¹, at 20 cGy min⁻¹) high linear energy transfer (LET) ⁵⁶Fe radiation based on FTIR studies. Density Functional Theory calculations indicate homolytic bond scission as the primary mechanism for polymer disintegration upon radiation exposure. Films did not change in thickness during the course of radiation exposure. The successful demonstration of radiation-triggered drug release may lead to new classes of radio-protective platforms for developing countermeasures to biological damage from ionizing radiation.

The probability of human exposure to damaging radiation is increased in activities associated with long-term space flight, medical radiation therapies, and responses to nuclear accidents.

Assessing Autophagy During Retinoid Treatment of Breast Cancer Cells

Retinoids are derived from vitamin A through a multi-step process. Within a target cell, retinoids regulate gene expression by activating the retinoid acid receptors (RAR) and retinoid x receptors (RXR), which are ligand-dependent transcription factors. Besides its therapeutic use in dermatological disorders, all-trans retinoic acid (ATRA) is successfully utilized to treat acute promyelocytic leukemia (APL) patients. The use of ATRA in APL patients is the first example of clinically useful differentiation therapy. Therapeutic strategies aiming at cancer cell differentiation have great potential for solid tumors, including breast cancer. The few clinical studies conducted with ATRA in breast cancer are rather disappointing. However, these studies did not take into account the heterogeneity of the disease and were conducted on unselected cohorts of patients.We recently showed that ATRA treatment of breast cancer cells induces autophagy, a highly conserved process aiming at degrading and recycling superfluous or harmful cellular components. In addition, autophagy inhibition significantly increases the therapeutic activity of ATRA. This finding is of fundamental importance, since autophagy has a dual role in cancer. Whereas autophagy may be a protective mechanism during the initial phases of cancer development, it may support cancer cell survival in already established tumors. Furthermore, autophagy can lower or enhance therapeutic efficiency, depending on the tumor type and the anticancer agent considered. Therefore, it is important to investigate the role of autophagy in the context of specific tumors and therapeutic approaches. Accurate autophagy studies are challenging given the dynamic nature of the process and the difficulty of measuring the rate of autophagosome degradation (autophagic flux). In this chapter, we provide protocols for a careful assessment of the autophagic flux in ATRA treated 2D and 3D breast cancer cultures.

ALDH as a Stem Cell Marker in Solid Tumors

Aldehyde dehydrogenase (ALDH) is an enzyme that participates in important cellular mechanisms as aldehyde detoxification and retinoic acid synthesis; moreover, ALDH activity is involved in drug resistance, a characteristic of cancer stem cells (CSCs). Even though ALDH is found in stem cells, CSCs and progenitor cells, this enzyme has been successfully used to identify and isolate cell populations with CSC properties from several tumor origins. ALDH is allegedly involved in cell differentiation through its product, retinoic acid. However, direct or indirect ALDH inhibition, using specific inhibitors or retinoic acid, has shown a reduction in ALDH activity, along with the loss of stem cell traits, reduction of cell proliferation, invasion, and drug sensitization. For these reasons, ALDH and retinoic acid are promising therapeutic targets. This review summarizes the current evidence for ALDH as a CSCs marker in solid tumors, as well as current knowledge about the functional roles of ALDH in CSCs. We discuss the controversy of ALDH activity to maintain CSC stemness, or conversely, to promote cell differentiation. Finally, we review the advances in using ALDH inhibitors as anti-cancer drugs.

Red meat and processed meat intake and risk for cutaneous melanoma in white women and men: Two prospective cohort studies

BACKGROUND

Red and processed meat consumption has been associated with increased risk for several cancers, but the association with cutaneous melanoma risk has been inconclusive.

OBJECTIVE

To investigate the association between red and processed meat intake and melanoma risk.

METHODS

Dietary information was assessed by using food frequency questionnaires in 2 prospective cohorts: 75,263 women from the Nurses' Health Study (1984-2010) and 48,523 men from the Health Professionals Follow-up Study (1986-2010). Melanoma cases were confirmed by reviewing pathology records. Pooled multivariable hazard ratios and 95% confidence intervals were estimated by using Cox proportional hazards models.

RESULTS

A total of 679 female and 639 male melanoma cases were documented during follow-up. Red and processed meat intake was inversely associated with melanoma risk (P = .002 for trend); the pooled hazard ratios (95% confidence intervals) of the 2 cohorts were 1.00 (reference), 1.00 (0.87-1.14), 0.98 (0.86-1.13), 0.89 (0.77-1.02), and 0.81 (0.70-0.95) for increasing quintiles of intake.

LIMITATIONS

Findings might have limited generalizability, considering that the cohorts were limited to white health professionals.

CONCLUSION

Red and processed meat intake was inversely associated with melanoma risk in these 2 cohorts.

Why Differentiation Therapy Sometimes Fails: Molecular Mechanisms of Resistance to Retinoids

Retinoids represent a popular group of differentiation inducers that are successfully used in oncology for treatment of acute promyelocytic leukemia in adults and of neuroblastoma in children. The therapeutic potential of retinoids is based on their key role in the regulation of cell differentiation, growth, and apoptosis, which provides a basis for their use both in cancer therapy and chemoprevention. Nevertheless, patients treated with retinoids often exhibit or develop resistance to this therapy. Although resistance to retinoids is commonly categorized as either acquired or intrinsic, resistance as a single phenotypic feature is usually based on the same mechanisms that are closely related or combined in both of these types. In this review, we summarize the most common changes in retinoid metabolism and action that may affect the sensitivity of a tumor cell to treatment with retinoids. The availability of retinoids can be regulated by alterations in retinol metabolism or in retinoid intracellular transport, by degradation of retinoids or by their efflux from the cell. Retinoid effects on gene expression can be regulated via retinoid receptors or via other molecules in the transcriptional complex. Finally, the role of small-molecular-weight inhibitors of altered cell signaling pathways in overcoming the resistance to retinoids is also suggested.

Pilosebaceous targeting by isotretenoin-loaded invasomal gel for the treatment of eosinophilic pustular folliculitis: optimization, efficacy and cellular analysis

CONTEXT

Eosinophilic pustular folliculitis is a secondary symptom associated with HIV infection appears as levels of CD4 lymphocyte cells and T4 lymphocyte cell. Isotretinoin, an analog of vitamin A (retinoid) alters the DNA transcription mechanism and interferes in the process of DNA formation. It also inhibits the eosinophilic chemotactic factors present in sebaceous lipids and in the stratum corneum of patients suffering from this ailment.

OBJECTIVE

The present research was aimed to formulate isotretenoin-loaded invasomal gel to deliver and target the drug to pilosebaceous follicular unit.

METHODS

Nine invasomal formulations (F1-F9) were prepared applying 3² factorial designs and characterized.

RESULTS

Formulation F9 was selected as optimized formulation due to optimum results and highest %CDP of 85.94 ± 1.86% in 8 h. Transmission electron microscopy (TEM) suggested uniformity in vesicles shape and size in F9 and developed as invasomal gel (IG).

LIMITATIONS

Clinical phase-I, phase-II, and phase-III studies will be required before using on human patients.

CONCLUSION

Confocal laser scanning microscopy (CLSM) validates that IG successfully reaches the pilosebaceous follicular unit and further studied on cell line (SZ-95) exhibited IC50 of ≤8 (25 μM of isotretenoin). Cell cycle analysis confirmed IG arrested the cell growth up to 82% with insignificant difference to pure isotretenion.

Biomarkers of Nutrition for Development (BOND)-Vitamin A Review

The Biomarkers of Nutrition for Development (BOND) project is designed to provide evidence-informed advice to anyone with an interest in the role of nutrition in health. The BOND program provides information with regard to selection, use, and interpretation of biomarkers of nutrient exposure, status, function, and effect, which will be especially useful for readers who want to assess nutrient status. To accomplish this objective, expert panels are recruited to evaluate the literature and to draft comprehensive reports on the current state of the art with regard to specific nutrient biology and available biomarkers for assessing nutritional status at the individual and population levels. Phase I of the BOND project includes the evaluation of biomarkers for 6 nutrients: iodine, folate, zinc, iron, vitamin A, and vitamin B-12. This review of vitamin A is the current article in this series. Although the vitamin was discovered >100 y ago, vitamin A status assessment is not trivial. Serum retinol concentrations are under homeostatic control due in part to vitamin A's use in the body for growth and cellular differentiation and because of its toxic properties at high concentrations. Furthermore, serum retinol concentrations are depressed during infection and inflammation because retinol-binding protein (RBP) is a negative acute-phase reactant, which makes status assessment challenging. Thus, this review describes the clinical and functional indicators related to eye health and biochemical biomarkers of vitamin A status (i.e., serum retinol, RBP, breast-milk retinol, dose-response tests, isotope dilution methodology, and serum retinyl esters). These biomarkers are then related to liver vitamin A concentrations, which are usually considered the gold standard for vitamin A status. With regard to biomarkers, future research questions and gaps in our current understanding as well as limitations of the methods are described.

Supplementation with vitamin A enhances oxidative stress in the lungs of rats submitted to aerobic exercise

Exercise training induces reactive oxygen species production and low levels of oxidative damage, which are required for induction of antioxidant defenses and tissue adaptation. This process is physiological and essential to improve physical conditioning and performance. During exercise, endogenous antioxidants are recruited to prevent excessive oxidative stress, demanding appropriate intake of antioxidants from diet or supplements; in this context, the search for vitamin supplements that enhance the antioxidant defenses and improve exercise performance has been continuously increasing. On the other hand, excess of antioxidants may hinder the pro-oxidant signals necessary for this process of adaptation. The aim of this study was to investigate the effects of vitamin A supplementation (2000 IU/kg, oral) upon oxidative stress and parameters of pro-inflammatory signaling in lungs of rats submitted to aerobic exercise (swimming protocol). When combined with exercise, vitamin A inhibited biochemical parameters of adaptation/conditioning by attenuating exercise-induced antioxidant enzymes (superoxide dismutase and glutathione peroxidase) and decreasing the content of the receptor for advanced glycation end-products. Increased oxidative damage to proteins (carbonylation) and lipids (lipoperoxidation) was also observed in these animals. In sedentary animals, vitamin A decreased superoxide dismutase and increased lipoperoxidation. Vitamin A also enhanced the levels of tumor necrosis factor alpha and decreased interleukin-10, effects partially reversed by aerobic training. Taken together, the results presented herein point to negative effects associated with vitamin A supplementation at the specific dose here used upon oxidative stress and pro-inflammatory cytokines in lung tissues of rats submitted to aerobic exercise.

Photodecomposition, photomutagenicity and photocytotoxicity of retinyl palmitate under He-Ne laser photoirradiation and its effects on photodynamic therapy of cancer cells in vitro

OBJECTIVE

Our aim was to study photodecomposition, photomutagenicity and cytotoxicity of retinyl palmitate (RP), a principal storage form of vitamin A in humans and animals, under He-Ne laser photoirradiation. Moreover, the effect of different concentrations and timing protocol of antioxidants on photodynamic therapy (PDT) is contradictory, so the effect of RP (as antioxidant) on the PDT cytotoxicity was studied.

METHODS

Photomutagenicity was tested by Ames test. Photodecomposition was studied by UV-vis spectroscopy. Cytotoxicity was measured with MTT-assay. Moreover, the effect of PDT, using hematoporphyrin derivatives (HpD) as photosensitizer under He-Ne laser irradiation (10 J/cm(2)), was studied on HeLa cells either with or without RP (1-100 μM) which incubated with the cells for short or long incubation period (1 h or 24 h) prior to PDT.

RESULTS

No photodecomposition of RP alone was obseved whereas there is a little photodecomposition of RP only in presence of HpD under irradiation with He-Ne laser. Moreover, no photomutagenicity was observed in Salmonella typhimurium strains under laser irradiation in presence or absence of HpD. RP alone (1-100 μM) significantly decrease the viability of HeLa cells. Laser irradiation of HeLa cells pre-incubated with RP alone for 24 h showed further significant decrease in viability of the cells. While RP incubations for 1 h before PDT had slight effect on the cells, 24 h incubation before PDT enhanced the cytotoxicity of PDT on HeLa cells.

CONCLUSIONS

RP can be used 24 h before PDT to enhance its effects. RP is not mutagenic under irradiation with He-Ne laser.

Vitamins and Melanoma

A tremendous amount of information was published over the past decades in relation to the role of vitamins in various neoplastic diseases. In particular, several studies showed an inverse relationship between selected vitamins intake and cancer risk. In this review we will focus on the role played by vitamins in melanoma with particular regard to vitamin A, D, K, E and C. Given that vitamin supplementation is easy, convenient, and readily accepted by patients, in the future the use of vitamins in chemoprevention and therapy of melanoma could be encouraged if supported by pre-clinical and clinical evidence.

Xeroderma pigmentosa: three new cases with an in depth review of the genetic and clinical characteristics of the disease

Xeroderma pigmentosum (XP) is a rare autosomal recessive disorder characterized by hypersensitivity of the skin and eyes to UV-radiation as a result of a defect in one of eight genes. Seven genes (XPA-XPG) have a defect in Nucletoide Excision Repair (NER), while the eighth gene XPV has a defect in polymerase η, which is responsible for replication of UV-damaged DNA to produce corrected daughter strands. We present the varied clinical courses of three African-American female patients with XP. Additionally, we present a review of the literature that focuses on the various clinical manifestations as well as the genetic and molecular mechanisms underlying this disease.

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.

Vitamin A intake and risk of melanoma: a meta-analysis

BACKGROUND

Mounting evidence from experimental and animal studies suggests that vitamin A may have a protective effect on melanoma, but the findings on the association of vitamin A intake with risk of melanoma have been inconsistently reported in epidemiologic studies. We attempted to elucidate the association by performing a meta-analysis.

METHODS

Eligible studies were identified by searching PubMed and EMBASE databases, as well as by reviewing the references of retrieved publications. Summary odds ratios (OR) with corresponding 95% confidence interval (CI) were computed with a random-effects model. Study-specific ORs and 95% CIs for the highest vs. lowest categories of vitamin A intake were pooled.

RESULTS

A total of 8 case-control studies and 2 prospective studies comprising 3,328 melanoma cases and 233,295 non-case subjects were included. The summary OR for the highest compared with the lowest intake of total vitamin A, retinol and beta-carotene was 0.86 (95% CI = 0.59-1.25), 0.80 (95% CI = 0.69-0.92) and 0.87 (95%CI = 0.62-1.20), respectively. Significant heterogeneity was observed among studies on vitamin A and beta-carotene intake, but not among studies on retinol intake. Subgroup and sensitivity analyses confirmed these findings. There was no indication of publication bias.

CONCLUSION

Findings from this meta-analysis suggest that intake of retinol, rather than of total vitamin A or beta-carotene, is significantly associated with reduced risk of melanoma.

Retinoic acid signaling pathways in development and diseases

Retinoids comprise a group of compounds each composed of three basic parts: a trimethylated cyclohexene ring that is a bulky hydrophobic group, a conjugated tetraene side chain that functions as a linker unit, and a polar carbon-oxygen functional group. Biochemical conversion of carotenoid or other retinoids to retinoic acid (RA) is essential for normal regulation of a wide range of biological processes including development, differentiation, proliferation, and apoptosis. Retinoids regulate various physiological outputs by binding to nuclear receptors called retinoic acid receptors (RARs) and retinoid X receptors (RXRs), which themselves are DNA-binding transcriptional regulators. The functional response of RA and their receptors are modulated by a host of coactivators and corepressors. Retinoids are essential in the development and function of several organ systems; however, deregulated retinoid signaling can contribute to serious diseases. Several natural and synthetic retinoids are in clinical use or undergoing trials for treating specific diseases including cancer. In this review, we provide a broad overview on the importance of retinoids in development and various diseases, highlighting various retinoids in the drug discovery process, ranging all the way from retinoid chemistry to clinical uses and imaging.

Retinoids for preventing the progression of cervical intra-epithelial neoplasia

BACKGROUND

Invasive cervical carcinoma is preceded by a precancerous phase, cervical intra-epithelial neoplasia (CIN), which can be detected on cervical smears and confirmed by colposcopy and biopsy. Moderate and severe cases of intra-epithelial neoplasia (CIN2 and CIN3) are treated mainly with surgery to prevent progression to invasive carcinoma. Medical methods of preventing the progression or inducing the regression of CIN are needed. Retinoids are potent modulators of epithelial cell growth and differentiation that may have potential for the treatment of CIN.

OBJECTIVES

To ascertain whether retinoids can cause regression or prevent progression of CIN.

SEARCH METHODS

We searched the Cochrane Gynaecological Cancer Review Group's Specialised Register and Non-Trials Database, the Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 3, 2010), and MEDLINE and EMBASE (July 2010).For the 2013 update, the searches were re-run as follows: CENTRAL, Issue 3, 2013; MEDLINE, April, Week 2, 2013; and EMBASE, Week 16, 2013.

SELECTION CRITERIA

Randomized controlled trials (RCTs) and non-RCTs of retinoids for treating CIN in women.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data from the trials. Adverse effects information was also collected from the trials.

MAIN RESULTS

Five RCTs comparing the efficacy of four different retinoids were identified. Two studies examined the effects on CIN2 and CIN3 of the retinoids N-(4-hydroxyphenyl)retinamide (fenretinide) and 9-cis-retinoic acid (aliretinoin) given orally. Two examined the effect of all-trans-retinoic acid administered topically to the cervix. The fifth study investigated the use of 13-cis-retinoic acid (isotretinoin) given orally to human immunodeficiency virus (HIV)-positive participants with CIN1 and condyloma.Four studies reported no significant effect of retinoids on the progression to higher grades of CIN, and the fifth did not report data on progression. In all studies retinoids had no significant effect on regression of CIN3. Two studies reported that retinoids were associated with regression of CIN2. One reported a greater complete regression of CIN2 over that seen with placebo, which was of borderline statistical significance (odds ratio (OR) 0.5, 95% confidence interval (CI) 0.25 to 1.02). The other study reported a nonsignificant dose-related trend toward increased rates of complete and partial regression compared with placebo. One study reported significantly worse outcomes in women receiving retinoid (OR for regression 6.00, 95% CI 1.00 to 35.91). In general, the retinoid medications were well tolerated.In the 2010 review and in this update, no new studies were identified for inclusion.

AUTHORS' CONCLUSIONS

The retinoids studied are not effective in causing regression of CIN3 but may have some effect on CIN2. The data on CIN1 are inadequate. Retinoids are not effective in preventing progression of CIN of any grade. At the doses given for the duration of treatment studied, the retinoids were reasonably well tolerated.

Conformational Analysis of Retinoic Acids: Effects of Steric Interactions on Nonplanar Conjugated Polyenes

Retinoic acids and other vitamin A analogs contain a trimethylcyclohexenyl ring in conjugation with a polyene chain joined at carbon-6 (C6) and carbon-7 (C7). A MP2-SCS/cc-pVDZ// B3LYP/6-31G(d) 2-D potential energy surface was computed for all-trans retinoic acid, which had 6 minima (3 enantiomeric pairs). The global minima were distorted s-gauche enantiomers (_6-7 = 53°) with half-chair conformations of the ring. Distorted s-gauche enantiomers (_6-7 = 55°) with inverted half-chair ring conformations were 1.7 kJ/mol above the global minima. The s-trans enantiomers (_6-7 = 164°) were 11.3 kJ/mol above the global minima. Steric energies were computed by the method of Guo and Karplus to identify key structural elements in retinoic acids which determines their conformation. Small molecule crystal structures in the CCDC database with trimethylcyclohexenyl ring and exocyclic double bonds have ring-chain geometries near to one of the 6 energy minima of retinoic acids, except for retinaldehyde iminium cations.

Retinoic acid-induced HOXA5 expression is co-regulated by HuR and miR-130a

Retinoic acid (RA) has been used as a chemopreventive agent for breast cancer. It has been shown that HOXA5 is a critical mediator of RA-induced cell growth inhibition. However, the molecular mechanisms underlying RA-induced HOXA5 expression remain largely unknown. Here we report that in addition to transcriptional regulation, post-transcriptional regulation also contributes to RA-induced HOXA5 expression. miR-130a, a c-Myc responsive miRNA, represses HOXA5 cellular levels under unstressed condition. Upon RA treatment, c-Myc is quickly degraded via the proteasome-dependent pathway. This in turn decreases miR-130a levels and de-represses the translation of HOXA5. We also show that the de-repression of HOXA5 translation is dependent on the RNA-binding protein Human antigen R (HuR), which binds to 3'UTR of HOXA5 mRNA and increases its stability in response to RA treatment. Collectively, these results demonstrate that HuR and miR-130a dynamically regulate HOXA5 gene expression via modulating HOXA5 mRNA turnover and translation, respectively, thereby contributing to RA-induced growth inhibition.

All-trans retinoic acid protects hepatocellular carcinoma cells against serum-starvation-induced cell death by upregulating collagen 8A2

As a therapeutic or chemopreventative agent for various cancers, all-trans retinoic acid (atRA) has been reported to inhibit growth, induce apoptosis or cause differentiation. It was found that atRA could protect hepatocellular carcinoma (HCC) cells against cell death induced by serum starvation. Furthermore, it was found that atRA could enhance cell adhesion, but had no effect on the cell cycle and apoptosis. Using an Illumina Human HT-12 v4 expression microarray, 207 upregulated and 173 downregulated genes were identified in HepG2 cells treated with atRA. The most upregulated genes are cytochrome P450 family 26 subfamily A polypeptide 1 (CYP26A1), histidine triad nucleotide binding protein 3 (HINT3), miR-1282 and cytochrome P450 family 26 subfamily B polypeptide 1 (CYP26B1), which showed more than fivefold greater expression. Using Gene Ontology analysis, the greatest significance was found in extracellular-matrix-related molecular functions and the cellular component in upregulated genes. The upregulation of collagen 8A2 (COL8A2) was further confirmed using quantitative RT-PCR and western blotting. Knockdown of COL8A2 blocked enhancement in the early stage of cell adhesion by atRA treatment. Re-expression of COL8A2 in COL8A2-knocked-down HCC cells reversed the effect of small interfering RNA-COL8A2. In addition, COL8A2 could increase HCC cell migration and invasion. Thus, COL8A2 was identified as the key protein involved in the enhancement of cell adhesion of atRA under serum-free conditions. In conclusion, atRA protects HCC cells against serum-starvation-induced cell death by enhancing cell adhesion, and COL8A2 plays an important role in HCC cell migration and invasion.

Retinoic acid therapy in patients with radioiodine negative differentiated thyroid cancer and clinical or biochemical evidence of disease: An initial experience

BACKGROUND

Dedifferentiation of thyroid follicular cells renders radioiodine therapy ineffective in patients of differentiated thyroid cancer (DTC). An alternative therapy to treat the disease or reinduce radioiodine uptake is necessary.

MATERIALS AND METHODS

We evaluated the role of retinoic acid therapy in 13 cases of DTC with raised thyroglobulin and/or clinically evident disease. Retinoic acid was given in a dose of 1.5 mg/kg for a period ranging between 1.5 and 18 months.

RESULTS

Age of the patients was between 18 and 65 years with a median of 49 years. Ten patients had papillary while two had follicular and one patient had mixed papillary and follicular thyroid cancer. Mean radioiodine given before starting retinoic acid was 164 mCi. Mean duration of therapy was 6.4 months. Thyroglobulin decreased in 2 patients and increased in 11 patients at the end of therapy. Radioiodine uptake was demonstrable in six patients, though faintly, while 7 cases showed no uptake. Based on the clinical and biochemical parameters, four patients had progressive disease, eight had stable disease and one patient showed partial response. Of the six patients with reinduction of radioiodine uptake, three had biochemical progression and the other three had stable disease.

CONCLUSION

Our findings suggest that retinoic acid therapy may induce radioiodine uptake and reduce serum thyroglobulin levels in some patients with DTC, but whether this results in clinically significant response can only be ascertained on long-term follow-up.

Pharmacotherapy of actinic keratosis: an update

INTRODUCTION

Actinic keratosis (AK) represents the initial intraepidermal manifestation of abnormal keratinocyte proliferation, with the potential of progression to squamous cell carcinoma (SCC). Few visible AKs lead to the use of lesion-directed treatments, including ablative and/or surgical procedures. Multiple and/or the suspicion of subclinical (non-visible) AKs lead to the use of field-directed therapies, including topical and ablative treatments. Predicting which AK will progress to SCC is difficult, and so all are treated. The goals of treatment are to eliminate visible AKs and to treat subclinical (non-visible) AKs, minimizing their risk of progression to invasive SCC, while pursuing good cosmesis.

AREAS COVERED

This review discusses the prevention of AKs (such as ultraviolet light avoidance, sunscreen use, protective clothing, and frequent self-examinations, in addition to chemoprevention with retinoids, eflornithine, silymarin, and others). It also covers lesion-directed treatments (e.g., cryotherapy, electrodessication and curettage, and surgery). Field-directed treatments are also mentioned (including laser resurfacing, dermabrasion, chemical peels, topical immunomodulators (imiquimod and diclofenac), topical chemotherapeutic agents (5-fluorouracil and retinoids), and photodynamic therapy). Finally, newer and investigational treatments are discussed (including ingenol mebutate).

EXPERT OPINION

There is no panacea in the treatment of AKs. The current best approach is the sequential treatment with a lesion-directed and a field-directed therapy. Several combinations seem to work well; they just need to be selected based on the evidence and adjusted to patient needs, preferences and dermatologist expertise.

Skin cancer of the head and neck

The majority of skin cancers of the head and neck are nonmelanoma skin cancers (NMSC). Basal cell carcinoma and squamous cell carcinoma are the most frequent types of NMSC. Malignant melanoma is an aggressive neoplasm of skin, and the ideal adjuvant therapy has not yet been found, although various options for treatment of skin cancer are available to the patient and physician, allowing high cure rate and excellent functional and cosmetic outcomes. Sunscreen protection and early evaluation of suspicious areas remain the first line of defense against skin cancers.

L-NAME co-treatment prevent oxidative damage in the lung of adult Wistar rats treated with vitamin A supplementation

Based on the fact that vitamin A in clinical doses is a potent pro-oxidant agent to the lungs, we investigated here the role of nitric oxide (NO•) in the disturbances affecting the lung redox environment in vitamin A-treated rats (retinol palmitate, doses of 1000-9000 IU•kg(-1)•day(-1)) for 28 days. Lung mitochondrial function and redox parameters, such as lipid peroxidation, protein carbonylation and the level of 3-nytrotyrosine, were quantified. We observed, for the first time, that vitamin A supplementation increases the levels of 3-nytrotyrosine in rat lung mitochondria. To determine whether nitric oxide (NO •) or its derivatives such as peroxynitrite (ONOO-) was involved in this damage, animals were co-treated with the nitric oxide synthase inhibitor L-NAME (30 mg•kg(-1), four times a week), and we analysed if this treatment prevented (or minimized) the biochemical disturbances resulting from vitamin A supplementation. We observed that L-NAME inhibited some effects caused by vitamin A supplementation. Nonetheless, L-NAME was not able to reverse completely the negative effects triggered by vitamin A supplementation, indicating that other factors rather than only NO• or ONOO- exert a prominent role in mediating the redox effects in the lung of rats that received vitamin A supplementation.

Food consumption pattern in cervical carcinoma patients and controls

Background:

The uterine cervix is the second most common site of cancer among Indian women.Though the human papillomavirus has been demonstrated to be a causative agent for this cancer, a variety of other risk factors are in play, such as sexual and reproductive patterns, socioeconomic, hygienic practices, and diet. The accumulated evidence suggests that cervical cancer is preventable and is highly suitable for primary prevention. The dietary intake of antioxidants and vitamins like vitamin A, carotenoids, vitamin C, folacin and tocopherol is found to have protective effects against cancer of the cervix. Dietary data regarding cervical cancer are still scanty.

Objective:

The present study was therefore undertaken to study the dietary pattern among uterine cervical cancer patients and normal controls.

Materials and Methods:

A total of 60 consecutive patients and 60 controls were enrolled from a referral hospital during the year 2004. A schedule inclusive of the food frequency pattern and 24-h dietary recall along with the general information was administered to all the enrolled subjects to describe findings on the food consumption pattern along with other important factors.

Results:

The mean intake of energy, protein, vitamins, etc., between the cases and controls was not significantly different except for the vitamin C level. Serum vitamin E was found to have lower average in patients as compared to controls. The nutrient intake of cervical cancer patients and controls was grossly deficient in the socioeconomic group studied. With regard to the macronutrient intake, calorie and protein intakes showed a deficit of around 50% when compared to RDA.

Conclusion:

The food consumption profile was not significantly different between cervical cancer patients and normal controls.

Dose response of retinol and isotretinoin in the prevention of nonmelanoma skin cancer recurrence

Using data from a randomized, double blind, study of the efficacy of retinol or isotretinoin vs. placebo on recurrence of nonmelanoma skin cancer in high-risk subjects, a reanalysis of the original intent to treat analysis was performed in a dose-response format. Cox proportional hazards models describe the relationship between dose quartiles of isotretinoin and retinol use and time to first occurrence of squamous cell carcinoma (SCC) or basal cell carcinoma (BCC) in crude and adjusted models. Neither the isotretinoin nor retinol models showed any significance at any quartile for reduction in first BCC or SCC occurrence. Crude and adjusted retinol models show a statistically significant increase in risk of developing an SCC in the first quartile, whereas only the crude model shows a statistically significant increase in risk in the first quartile of the isotretinoin model. For retinol and SCC, hazard ratios (HRs) for the first quartile were as follows: HR = 2.92, 95% confidence interval (CI) = 1.67-5.10 crude; HR = 1.95, 95% CI = 1.00-3.80 adjusted. For isotretinoin and SCC, HRs for the first quartile were as follows: HR = 2.38, 95% CI = 1.35-4.19 crude; HR = 1.69, 95% CI = 0.87-3.31 adjusted. Test for trend was not significant in any of the models. These analyses confirm the results of the original intent to treat analyses and raise an interesting question related to the potential for increased risk for patients in the first quartile of retinol dose.

Broad-spectrum antiviral activity including human immunodeficiency and hepatitis C viruses mediated by a novel retinoid thiosemicarbazone derivative

Aromatic aldehyde-derived thiosemicarbazones 4-6, the S-substituted modified thiosemicarbazones 7/8, and a vitamin A-derived (retinoid) thiosemicarbazone derivative 12 were investigated as inhibitors of human hepatitis C virus (HCV) subgenomic RNA replicon Huh7 ET (luc-ubi-neo/ET) replication. Compounds 4-6 and 12 were found to be potent suppressors of HCV RNA replicon replication. The trifluoromethoxy-substituted thiosemicarbazone 6 and the retinoid thiosemicarbazone derivative 12 were even superior in selectivity to the included reference agent recombinant human alpha-interferon-2b, showing potencies in the nanomolar range of concentration. In addition, compounds 5, 6, 8 and 12 were tested as inhibitors of cytopathic effect (CPE) induced by human varicella-zoster virus (VZV) and/or human cytomegalovirus (HCMV). Compounds 4-6, 8 and 12 were additionally examined as inhibitors of CPE induced by cowpox virus and vaccinia virus. Thiosemicarbazone 4 was inhibitory on cowpox and vaccinia virus replication comparable in potency and selectivity to the reference agent cidofovir. Retinoid thiosemicarbazone derivative 12 was active as micromolar inhibitor of VZV, HCMV, and, in addition, human immunodeficiency virus type 1 (HIV-1) replication. These results indicate that thiosemicarbazone derivatives are appropriate lead structures to be evaluated in targeted antiviral therapies for hepatitis C (STAT-C), and that the vitamin A-related thiosemicarbazone derivative 12 emerges as a broad-spectrum antiviral agent, co-suppressing the multiplication of important RNA and DNA viruses.

Non-surgical treatments of primary, non-melanoma eyelid malignancies: a review

The diagnosis and management of periocular cutaneous malignancies are essential components of an ophthalmologist's practice. Skin cancers comprise nearly one-third of newly diagnosed malignancies. Furthermore, the incidence of skin cancer appears to be increasing. Multiple treatment modalities exist for periocular cutaneous malignancy. Surgical extirpation, often with the combined expertise of a Mohs micrographic surgeon, is typically the first line therapy and is often curative in the periocular region, depending on a variety of factors, including tumour histology, specific location, depth of invasion and surgical technique. However, there are instances where a less invasive, non-surgical treatment option is warranted, including patients who are poor surgical risks or those with diffuse disease. The purpose of this article is to review the literature and describe the non-surgical treatment options, indications and efficacies for non-melanoma primary eyelid malignancies.

Retinoic acid: a key player in immunity

For the past 100 years, vitamin A has been implicated as an essential dietary component in host resistance to infectious disease. However, only recently have studies begun to elucidate the cellular and molecular mechanisms of how vitamin A regulates cell-mediated and humoral-mediated immunity. In this review, we present an overview of the recent discoveries of the role that vitamin A and its metabolite, retinoic acid (RA), play in the regulation of immune cells. How RA impacts on leukocyte growth, differentiation, and homing is discussed with special attention to inflammatory responses and solid tumor microenvironment.

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.

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.

From carrot to clinic: an overview of the retinoic acid signaling pathway

Vitamin A is essential for the formation and maintenance of many body tissues. It is also important for embryonic growth and development and can act as a teratogen at critical periods of development. Retinoic acid (RA) is the biologically active form of vitamin A and its signaling is mediated by the RA and retinoid X receptors. In addition to its role as an important molecule during development, RA has also been implicated in clinical applications, both as a potential anti-tumor agent as well as for the treatment of skin diseases. This review presents an overview of how dietary retinoids are converted to RA, hence presenting the major players in RA metabolism and signaling, and highlights examples of treatment applications of retinoids. Moreover, we discuss the origin and diversification of the retinoid pathway, which are important factors for understanding the evolution of ligand-specificity among retinoid receptors.

Activation of Multiple Molecular Mechanisms for Increasing Apoptosis in Human Glioblastoma T98G Xenograft

Glioblastoma is the most malignant brain tumor of astroglial origin. It renders poor response or resistance to existing therapeutics. We used all-trans retinoic acid (ATRA) and interferon gamma (IFN-γ) alone and in combination for controlling human glioblastoma T98G xenografted in nude mice. Histopathological examination showed astrocytic differentiation in ATRA group, some apoptosis in IFN-γ group, and occurrence of differentiation and enhancement of apoptosis in ATRA plus IFN-γ group. ATRA plus IFN-γ induced extrinsic pathway of apoptosis by activation of caspase-8 and cleavage of Bid to tBid and also down regulation of hTERT, c-IAP2, and survivin and upregulation of Smac/Diablo to promote apoptosis. Mitochondrial release of apoptosis-inducing factor (AIF) induced caspase-independent pathway and also upregulation of calpain and caspase-dependent pathways ultimately activated caspase-3 for apoptosis. Increased activities of calpain and caspase-3 degraded 270 kD α-spectrin at the specific sites to generate 145 kD spectrin breakdown product (SBDP) and 120 kD SBDP, respectively. In situ TUNEL and double immunofluorescent labelings detected apoptosis with increased expression of calpain, caspase-12, caspase-3, and AIF in tumors after treatment with IFN-γ and most effectively with ATRA plus IFN-γ. Results indicated that ATRA plus IFN-γ activated multiple molecular mechanisms for increasing apoptosis in human glioblastoma in vivo.

Nutrition and Orthomolecular Supplementation in Lung Cancer Patients

This article reviews updates and provides some data related to nutritional and orthomolecular supplementation in oncology patients with an emphasis on lung cancer, a commonly diagnosed tumor with significant nutritional disturbances. Cancer and its treatment play a significant role in nutritional imbalance which likely has negative impact on the patient both in terms of quality and quantity of life. Nutritional supplementation may correct these imbalances with significant clinical benefit both physiologically and psychologically. This review will help assist in providing clinically useful data to assess the cancer patient’s nutritional status and to guide nutritional intervention to assist these patients’ recovery.

Bexarotene: a promising anticancer agent

Retinoids are biologically active derivatives of vitamin A, which play essential roles in embryonic or adult cell behavior modulating cell proliferation, differentiation and apoptosis. The biologic effects of retinoids are mediated by two distinct families of intracellular receptors: retinoid acid receptors (RARs)-α, -β and -γ and retinoid X receptors (RXR)-α, -β and -γ. Bexarotene is a selective RXR agonist, which exerts its effects in blocking cell cycle progression, inducing apoptosis and differentiation, preventing multidrug resistance, and inhibiting angiogenesis and metastasis, making it a promising chemopreventive agent against cancer.