The promise of retinoids to fight against cancer

Hierarchical self-recognition and response in CSC and non-CSC micro-niches for cancer therapy

Cancer stem cells (CSCs) characterized by self-renewal, invasiveness, tumorigenicity and resistance to treatment are regarded as the thorniest issues in refractory tumors. We develop a targeted and hierarchical controlled release nano-therapeutic platform (SEED-NPs) that self-identifies and responds to CSC and non-CSC micro-niches of tumors. In non-CSC micro-niche, reactive oxygen species (ROS) trigger the burst release of the chemotherapeutic drug and photosensitizer to kill tumor cells and reduce tumor volume by combining chemotherapy and photodynamic therapy (PDT). In CSC micro-niche, the preferentially released differentiation drug induces CSC differentiation and transforms CSCs into chemotherapy-sensitive cells. SEED-NPs exhibit an extraordinary capacity for downregulating the stemness of CD44+/CD24- SP (side population) cell population both in vitro and in vivo, and reveal a 4-fold increase of tumor-targeted accumulation. Also, PDT-generated ROS promote the formation of tunneling nanotubes and facilitate the divergent network transport of drugs in deep tumors. Moreover, ROS in turn promotes CSC differentiation and drug release. This positive-feedback-loop strategy enhances the elimination of refractory CSCs. As a result, SEED-NPs achieve excellent therapeutic effects in both 4T1 SP tumor-bearing mice and regular 4T1 tumor-bearing mice without obvious toxicities and eradicate half of mice tumors. SEED-NPs integrate differentiation, chemotherapy and PDT, which proved feasible and valuable, indicating that active targeting and hierarchical release are necessary to enhance antitumor efficacy. These findings provide promising prospects for overcoming barriers in the treatment of CSCs.

Monitoring alterations of all-trans-retinal in human brain cancer cells by label-free confocal Raman imaging: regulation of the redox status of cytochrome c

This article has shown the impact of all-trans-retinal on human brain cancer, which is apparent in the shifts in the redox status of cytochrome c in a single cell. The connection between cytochrome c expression and its role in cancer development remains relatively unexplored. To assess this, we employed Raman spectroscopy and imaging to determine the redox state of the iron ion in cytochrome c across different cellular locations, including mitochondria, cytoplasm, lipid droplets, and the endoplasmic reticulum within human brain cancer cells. We have analyzed normal human astrocytes (NHA) and two brain cancer cell lines (astrocytoma - CRL-1718 and glioblastoma - U-87 MG) without and supplemented with all-trans-retinal. Our results confirmed that human brain cancer cells demonstrate varying redox status compared to normal cells based on the established correlation between the intensity of the cytochrome c Raman band at 1583 cm-1 and the malignancy grade of brain cancer cells. Our research unveiled that all-trans-retinal induces remarkable changes in the mitochondrial functional activity (redox status) of cancer cells, which were measured by confocal Raman spectroscopy and imaging.

Vitamin A Status Modulates Epithelial Mesenchymal Transition in the Lung: The Role of Furin

Vitamin A deficiency (VAD) induced TGF-β hyperactivation and reduced expression of cell adhesion proteins in the lung, suggesting that the disruption of retinoic acid (RA) signaling leads to epithelial-mesenchymal transition (EMT). To elucidate the role of lung vitamin A status in EMT, several EMT markers and the expression of the proprotein convertase furin, which activates TGF-β, were analyzed in two experimental models. Our in vivo model included control rats, VAD rats, and both control rats and VAD rats, treated with RA. For the in vitro studies, human bronchoalveolar epithelial cells treated with RA were used. Our data show that EMT and furin are induced in VAD rats. Furthermore, furin expression continues to increase much more markedly after treatment of VAD rats with RA. In control rats and cell lines, an acute RA treatment induced a significant increase in furin expression, concomitant with changes in EMT markers. A ChIP assay demonstrated that RA directly regulates furin transcription. These results emphasize the importance of maintaining vitamin A levels within the physiological range since both levels below and above this range can cause adverse effects that, paradoxically, could be similar. The role of furin in EMT is discussed.

Retinoids and EZH2 inhibitors cooperate to orchestrate anti-oncogenic effects on bladder cancer cells

The highly mutated nature of bladder cancers harboring mutations in chromatin regulatory genes opposing Polycomb-mediated repression highlights the importance of targeting EZH2 in bladder cancer. Furthermore, the critical role of the retinoic acid signaling pathway in the development and homeostasis of the urothelium, and the anti-oncogenic effects of retinoids are well established. Therefore, our aim is to simultaneously target EZH2 and retinoic acid signaling in bladder cancer to potentiate the therapeutic response. Here we report that this coordinated targeting strategy stimulates an anti-oncogenic profile, as reflected by inducing a synergistic reduction in cell viability that was associated with increased apoptosis and cell cycle arrest in a cooperative and orchestrated manner. This study characterized anti-oncogenic transcriptional reprogramming centered on the transcriptional regulator CHOP by stimulating the endoplasmic reticulum stress response. We further portrayed a molecular mechanism whereby EZH2 maintains H3K27me3-mediated repression of a subset of genes involved in unfolded protein responses, reflecting the molecular mechanism underlying this co-targeting strategy. These findings highlight the importance of co-targeting the EZH2 and retinoic acid pathway in bladder cancers and encourage the design of novel treatments employing retinoids coupled with EZH2 inhibitors in bladder carcinoma.

Micronutrients Importance in Cancer Prevention-Vitamins

The effect of nutrition in the development and prognosis of cancer has received a lot of attention. Research shows taking vitamins, which are powerful antioxidants, can significantly lower the risk of cancers. Nutritional supplements suited to a patient's background, genetics, diet, tumour histology, and therapy may be beneficial in some cases. A poor diet may have a negative impact on immunity and treatment tolerance, decreasing the efficacy of chemotherapy in destroying malignant cells. Most cancer patients now take vitamins to supplement regular treatment and/or to decrease side effects from the medicine as well as the underlying ailment. This is a new development in recent decades, whereas taking nutritional supplements while receiving cancer treatment may increase the success of chemotherapy. To enhance the quality of life, lengthen the survival rate, and sustain immunotherapy compliance, additional study into the use of micronutrients in medical treatment is required for cancer patients. The main purpose of this book chapter was to highlight the role of vitamins in cancer and to establish a solid foundation for future research on this exciting topic. The possible impact of some vitamins in various malignancies such as colorectal, breast, prostate, lung, pancreatic, and stomach cancers are investigated.

Exploring the interactions of antihistamine with retinoic acid receptor beta (RARB) by molecular dynamics simulations and genome-wide meta-analysis

Kaposi sarcoma (KS) is one of the most common AIDS-related malignant neoplasms, which can leave lesions on the skin among HIV patients. These lesions can be treated with 9-cis-retinoic acid (9-cis-RA), an endogenous ligand of retinoic acid receptors that has been FDA-approved for treatment of KS. However, topical application of 9-cis-RA can induce several unpleasant side effects, like headache, hyperlipidemia, and nausea. Hence, alternative therapeutics with less side effects are desirable. There are case reports associating over-the-counter antihistamine usage with regression of KS. Antihistamines competitively bind to H1 receptor and block the action of histamine, best known for being released in response to allergens. Furthermore, there are already dozens of antihistamines that are FDA-approved with less side effects than 9-cis-RA. This led our team to conduct a series of in-silico assays to determine whether antihistamines can activate retinoic acid receptors. First, we utilized high-throughput virtual screening and molecular dynamics simulations to model high-affinity interactions between antihistamines and retinoic acid receptor beta (RARβ). We then performed systems genetics analysis to identify a genetic association between H1 receptor itself and molecular pathways involved in KS. Together, these findings advocate for exploration of antihistamines against KS, starting with our two promising hit compounds, bepotastine and hydroxyzine, for experimental validation study in the future.

Human nutritional relevance and suggested nutritional guidelines for vitamin A5/X and provitamin A5/X

In the last century, vitamin A was identified that included the nutritional relevant vitamin A1 / provitamin A1, as well as the vitamin A2 pathway concept. Globally, nutritional guidelines have focused on vitamin A1 with simplified recommendations and calculations based solely on vitamin A. The vitamin A / provitamin A terminology described vitamin A with respect to acting as a precursor of 11-cis-retinal, the chromophore of the visual pigment, as well as retinoic acid(s), being ligand(s) of the nuclear hormone receptors retinoic acid receptors (RARs) α, β and γ. All-trans-retinoic acid was conclusively shown to be the endogenous RAR ligand, while the concept of its isomer 9-cis-retinoic acid, being "the" endogenous ligand of the retinoid-X receptors (RXRs), remained inconclusive. Recently, 9-cis-13,14-dihydroretinoic acid was conclusively reported as an endogenous RXR ligand, and a direct nutritional precursor was postulated in 2018 and further confirmed by Rühl, Krezel and de Lera in 2021. This was further termed vitamin A5/X / provitamin A5/X. In this review, a new vitamin A5/X / provitamin A5/X concept is conceptualized in parallel to the vitamin A(1) / provitamin A(1) concept for daily dietary intake and towards dietary guidelines, with a focus on the existing national and international regulations for the physiological and nutritional relevance of vitamin A5/X. The aim of this review is to summarize available evidence and to emphasize gaps of knowledge regarding vitamin A5/X, based on new and older studies and proposed future directions as well as to stimulate and propose adapted nutritional regulations.

Targeting the retinoic acid signaling pathway as a modern precision therapy against cancers

Retinoic acid (RA) is a vital metabolite derived from vitamin A. RA plays a prominent role during development, which helps in embryological advancement and cellular differentiation. Mechanistically, RA binds to its definite nuclear receptors including the retinoic acid receptor and retinoid X receptor, thus triggering gene transcription and further consequences in gene regulation. This functional heterodimer activation later results in gene activation/inactivation. Several reports have been published related to the detailed embryonic and developmental role of retinoic acids and as an anti-cancer drug for specific cancers, including acute promyelocytic leukemia, breast cancer, and prostate cancer. Nonetheless, the other side of all-trans retinoic acid (ATRA) has not been explored widely yet. In this review, we focused on the role of the RA pathway and its downstream gene activation in relation to cancer progression. Furthermore, we explored the ways of targeting the retinoic acid pathway by focusing on the dual role of aldehyde dehydrogenase (ALDH) family enzymes. Combination strategies by combining RA targets with ALDH-specific targets make the tumor cells sensitive to the treatment and improve the progression-free survival of the patients. In addition to the genomic effects of ATRA, we also highlighted the role of ATRA in non-canonical mechanisms as an immune checkpoint inhibitor, thus targeting the immune oncological perspective of cancer treatments in the current era. The role of ATRA in activating independent mechanisms is also explained in this review. This review also highlights the current clinical trials of ATRA in combination with other chemotherapeutic drugs and explains the future directional insights related to ATRA usage.

Does isotretinoin affect spermatogenesis in the long term? A rat model

OBJECTIVES

Spermatogenesis, in which cell regeneration continues, can be affected by environmental, chemical, psychological factors or various diseases. There is conflicting information in the literature about the effect of isotretinoin, which is widely used in acne treatment, on testes and spermatogenesis. Therefore, we planned a rat study to evaluate the long-term efficacy of oral isotretinoin on testicular tissues and spermatogenesis.

MATERIALS AND METHODS

The Group 1 (n = 6) 7.5 mg/kg/day and the Group 2 (n = 6) received isotretinoin at a dose of 30 mg/kg/day dissolved in sunflower oil, the Sham Group (n = 6) received only sunflower oil by gavage, and the control group (n = 6) received standard feed and water for four weeks. After the 4th week, all animals were fed with standard feed and water and followed for the next four weeks. At the end of the 8th week, all animals were sacrificed under deep anesthesia. Seminiferous tubule diameters, epithelial thickness, apoptotic index, sperm number and motility recorded Results: Sperm count, motility, vitality, diameter of seminiferous tubule and germinal epithelium thickness were decreased and apoptotic index increased in the groups received isotretinoin. There was no significant difference between the groups in terms of testosterone levels.

CONCLUSIONS

We consider that further comprehensive studies, including human clinical trials, should be conducted to examine the negative effects of isotretinoin on spermatogenesis in the long term especially when there is a need using isotretinoin in men for various reasons and to eliminate the contradictions in the literature in this regard.

Vitamin A: a key coordinator of host-microbe interactions in the intestine

The human intestine is home to a dense community of microbiota that plays a key role in human health and disease. Nutrients are essential regulators of both host and microbial physiology and function as key coordinators of host-microbe interactions. Therefore, understanding the specific roles and underlying mechanisms of each nutrient in regulating the host-microbe interactions will be essential in developing new strategies for improving human health through microbiota and nutrient intervention. This review will give a basic overview of the role of vitamin A, an essential micronutrient, on human health, and highlight recent findings on the mechanisms by which it regulates the host-microbe interactions. [BMB Reports 2023; 56(3): 133-139].

CAR T-cells to treat brain tumors

Tremendous success using CAR T therapy in hematological malignancies has garnered significant interest in developing such treatments for solid tumors, including brain tumors. This success, however, has yet to be mirrored in solid organ neoplasms. CAR T function has shown limited efficacy against brain tumors due to several factors including the immunosuppressive tumor microenvironment, blood-brain barrier, and tumor-antigen heterogeneity. Despite these considerations, CAR T-cell therapy has the potential to be implemented as a treatment modality for brain tumors. Here, we review adult and pediatric brain tumors, including glioblastoma, diffuse midline gliomas, and medulloblastomas that continue to portend a grim prognosis. We describe insights gained from different preclinical models using CAR T therapy against various brain tumors and results gathered from ongoing clinical trials. Furthermore, we outline the challenges limiting CAR T therapy success against brain tumors and summarize advancements made to overcome these obstacles.

A transgenic reporter mouse model for in vivo assessment of retinoic acid receptor transcriptional activation

Background: Vitamin A is essential for a wide range of life processes throughout embryogenesis to adult life. With the aim of developing an in vivo model to monitor retinoic acid receptor (RAR) transactivation real-time in intact animals, we generated transgenic mice carrying a luciferase (luc) reporter gene under the control of retinoic acid response elements (RAREs) consisting of three copies of a direct repeat with five spacing nucleotides (DR5). Methods: Transgenic mice carrying a RARE dependent luciferase reporter flanked with insulator sequence were generated by pronuclear injection. RARE dependent luciferase activity was detected by in vivo imaging or in tissue extracts following manipulations with RAR/retinoid X receptor (RXR) agonists, RAR antagonists or in vitamin A deficient mice. Results: We found a strong induction of luciferase activity in a time and dose dependent manner by retinoic acid as well as RAR agonists, but not by the RXR agonist (using n=4-6 per group; 94 mice). In addition, luciferase activity was strongly reduced in vitamin A-deficient mice (n=6-9; 30 mice). These observations confirm that luciferase activity was controlled by RAR activation in the RARE-luc mouse. Luciferase activity was detectable in various organs, with high activity especially in brain and testis, indicating strong retinoid signalling in these tissues. Conclusion: The RARE-luc transgenic mice, which enabled real-time in vivo assessment of RAR activation, will be useful in understanding the normal physiology of vitamin A, the role of retinoid signalling in pathologies as well as to evaluate pharmacological ligands for RARs.

Fruit and vegetable consumption, pesticide residue intake from consumption of fruits and vegetables, and risk of uterine fibroids

OBJECTIVE

To examine the association between consumption of fruits and vegetables and pesticide residue intake from consumption of fruits and vegetables and risk of ultrasound- or hysterectomy-confirmed fibroids. Only a few studies have evaluated the association of fruit and vegetable intake with uterine fibroids, with inconsistent results. No studies have examined pesticide exposure through fruits and vegetables with fibroid risk.

DESIGN

Prospective cohort study. Cox proportional hazards models were used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs).

SETTING

Not applicable.

PATIENT(S)

A total of 81,782 premenopausal participants from the Nurses' Health Study II cohort were followed from 1991 to 2009 for fruit and vegetable analysis, and 49,927 participants were followed from 1999 to 2009 for pesticide residue burden analysis. Their diet was assessed every 4 years with a food frequency questionnaire. Fruits and vegetables were classified into high- or low-pesticide residues using a validated method based on surveillance data from the US Department of Agriculture.

INTERVENTION(S)

Not applicable.

MAIN OUTCOME MEASURE(S)

Cases of ultrasound- or hysterectomy-confirmed fibroids were identified from self-reports to validated questionnaires.

RESULT(S)

From 1991 to 2009, 9,706 incident cases of ultrasound- or hysterectomy-confirmed fibroids were reported, and 4,195 incident cases were identified from 1999 to 2009. No association was observed between total fruit and vegetable consumption and uterine fibroid risk. Participants with the highest intake of total fruits (≥4/day) were 10% less likely to develop uterine fibroids compared with participants who consumed <1/day (95% CI = 0.80-1.01). No associations were observed with any other fruit or vegetable groups. An inverse association was observed between intake of high-pesticide-residue fruits and vegetables and fibroid risk (HR for 5th vs. 1st quintile = 0.87; 95% CI = 0.77-0.99), while no association with low-pesticide-residue fruits and vegetables was observed (HR for 5th vs. 1st quintile = 1.08; 95% CI = 0.95-1.23).

CONCLUSION(S)

Our findings suggest that pesticide residues on fruits and vegetables are not associated with a higher risk of uterine fibroids. Furthermore, our results suggest that intake of fruits may be associated with a lower risk of fibroids. Future research in this area should focus on dietary exposures across the life course as well as assessment of class-specific pesticides.

Epigenetic compounds targeting pharmacological target lysine specific demethylase 1 and its impact on immunotherapy, chemotherapy and radiotherapy for treatment of tumor recurrence and resistance

It has been proven that metastatic recurrence and therapeutic resistance are linked. Due to the variability of individuals and tumors, as well as the tumor's versatility in avoiding therapies, therapy resistance is more difficult to treat. Therapy resistance has significantly restricted the clinical feasibility and efficacy of tumor therapy, despite the discovery of novel compounds and therapy combinations with increasing efficacy. In several tumors, lysine specific demethylase 1 (LSD1) has been associated to metastatic recurrence and therapeutic resistance. For researchers to better comprehend how LSD1-mediated tumor therapy resistance occurs and how to overcome it in various tumors, this study focused on the role of LSD1 in tumor recurrence and therapeutic resistance. The importance of therapeutically targeted LSD1 was also discussed. Most gene pathway signatures are related to LSD1 inhibitor sensitivity. However, some gene pathway signatures, especially in AML, negatively correlate with LSD1 inhibitor sensitivity, but targeting LSD1 makes the therapy-resistant tumor sensitive to physiological doses of conventional therapy. We propose that combining LSD1 inhibitor with traditional tumor therapy can help patients attain a complete response and prevent cancer relapse.

ERK MAP Kinase Signaling Regulates RAR Signaling to Confer Retinoid Resistance on Breast Cancer Cells

Retinoic acid (RA) and its synthetic derivatives, retinoids, have been established as promising anticancer agents based on their ability to regulate cell proliferation and survival. Clinical trials, however, have revealed that cancer cells often acquire resistance to retinoid therapy. Therefore, elucidation of underlying mechanisms of retinoid resistance has been considered key to developing more effective use of retinoids in cancer treatment. In this study, we show that constitutive activation of ERK MAP kinase signaling, which is often caused by oncogenic mutations in RAS or RAF genes, suppresses RA receptor (RAR) signaling in breast cancer cells. We show that activation of the ERK pathway suppresses, whereas its inhibition promotes, RA-induced transcriptional activation of RAR and the resultant upregulation of RAR-target genes in breast cancer cells. Importantly, ERK inhibition potentiates the tumor-suppressive activity of RA in breast cancer cells. Moreover, we also reveal that suppression of RAR signaling and activation of ERK signaling are associated with poor prognoses in breast cancer patients and represent hallmarks of specific subtypes of breast cancers, such as basal-like, HER2-enriched and luminal B. These results indicate that ERK-dependent suppression of RAR activity underlies retinoid resistance and is associated with cancer subtypes and patient prognosis in breast cancers.

Novel pH-sensitive nanoparticles based on prodrug strategy to delivery All-Trans Retinoic Acid for breast cancer

Developing chemotherapy with nanoparticle-based prodrugs provides promising strategies for improving the safety and delivery of anti-cancer drugs therapeutics and effective cancer treatment. Herein, we developed a pH-sensitive prodrug delivery system (All-Trans-Retinoic Acid (ATRA) grafted poly (β-amino esters) (PBAE) copolymers, ATRA-g-PBAE) for delivery of ATRA with some physicochemical and biological properties. The in vitro release of ATRA-g-PBAE prodrug nanoparticles (PNPs) was sustained-release and pH-sensitive. The cytotoxicity and uptake of different preparations in vitro were evaluated on MCF-7 cells at pH 7.4 and 5.5. The carrier PBAE had no cytotoxicity, and ATRA-g-PBAE PNPs could significantly inhibit cell growth at pH 5.5. MCF-7 cells treated with Cy5.5 grafted PBAE (Cy5.5-PBAE) showed stronger fluorescence signals at pH 5.5. Meanwhile, ATRA-g-PBAE PNPs entered the cell via a clathrin-mediated endocytic pathway. Subsequently, PBAE protonation facilitated the escape of PNPs from the lysosome and released the drug. ATRA-g-PBAE seems promising as a novel pH-sensitive prodrug to overcome the limitations of ATRA for breast cancer therapy.

Neurospora crassa is a potential source of anti-cancer agents against breast cancer

Fungi are an excellent source of pharmaceuticals including anti-tumor agents. Neurospora crassa generates metabolites with diverse structural classes, however, its potential as an anti-tumor agent source has not been explored. The purpose of this study aimed to investigate the potential of Neurospora crassa mixture against breast cancer. The in vitro T-47D and MDA-MB-231 experiments showed that N. crassa mixture at the concentrations of both 1.7 and 0.85 µg/ml significantly inhibited tumor cell proliferation, migration and invasion, and 3D spheroid formation. However, the inhibition rates of MCF-10A ranged 10-20% at concentrations of 0.85 and 1.7 µg/ml. The mixture at the concentration of 0.85 µg/ml could significantly downregulate the expressions of transcription factors of E2F1 and E2F3, cancer stem cell-related genes of LIN28, HIWI, and CD133, and onco-lncRNA HOTAIR, and increase CASP3 activity in either T-47D or MDA-MD-231 breast cancer cell lines. In vivo breast cancer C3H mouse model results showed that N. crassa mixture significantly inhibited tumor growth. These findings suggest that N. crassa contains an antitumor component(s) against breast cancer invasiveness, which may inhibit the self-renewal and differentiation of breast cancer stem cells possibly by downregulating cancer stem cell-associated and/or transcription factor genes and oncogenes, and promoting apoptosis.

The Sin3A/MAD1 Complex, through Its PAH2 Domain, Acts as a Second Repressor of Retinoic Acid Receptor Beta Expression in Breast Cancer Cells

Retinoids are essential in balancing proliferation, differentiation and apoptosis, and they exert their effects through retinoic acid receptors (RARs) and retinoid X receptors (RXRs). RARβ is a tumor-suppressor gene silenced by epigenetic mechanisms such as DNA methylation in breast, cervical and non-small cell lung cancers. An increased expression of RARβ has been associated with improved breast cancer-specific survival. The PAH2 domain of the scaffold protein SIN3A interacts with the specific Sin3 Interaction Domain (SID) of several transcription factors, such as MAD1, bringing chromatin-modifying proteins such as histone deacetylases, and it targets chromatin for specific modifications. Previously, we have established that blocking the PAH2-mediated Sin3A interaction with SID-containing proteins using SID peptides or small molecule inhibitors (SMI) increased RARβ expression and induced retinoic acid metabolism in breast cancer cells, both in in vitro and in vivo models. Here, we report studies designed to understand the mechanistic basis of RARβ induction and function. Using human breast cancer cells transfected with MAD1 SID or treated with the MAD SID peptide, we observed a dissociation of MAD1, RARα and RARβ from Sin3A in a coimmunoprecipitation assay. This was associated with increased RARα and RARβ expression and function by a luciferase assay, which was enhanced by the addition of AM580, a specific RARα agonist; EMSA showed that MAD1 binds to E-Box, similar to MYC, on the RARβ promoter, which showed a reduced enrichment of Sin3A and HDAC1 by ChIP and was required for the AM580-enhanced RARβ activation in MAD1/SID cells. These data suggest that the Sin3A/HDAC1/2 complex co-operates with the classical repressors in regulating RARβ expression. These data suggest that SIN3A/MAD1 acts as a second RARβ repressor and may be involved in fine-tuning retinoid sensitivity.

The RIG-I-NRF2 axis regulates the mesenchymal stromal niche for bone marrow transplantation

Bone marrow-derived mesenchymal stem cells (BMSCs) support bone formation and constitute the stromal niche in regulating hematopoietic stem cells (HSCs). Stromal niche dysfunction affects HSC engraftment during transplantation; however, the underlying mechanisms remain elusive. In the present study, we found that all-trans retinoic acid (ATRA) and inflammation stress upregulated retinoic acid-inducible gene I (RIG-I) in BMSCs. Excess RIG-I expression damaged the clonogenicity, bone-forming ability of BMSCs and, particularly, their stromal niche function that supports HSC expansion in vitro and engraftment in vivo. Mechanistically, RIG-I elevation promoted the degradation of NRF2, a checkpoint for antioxidant cellular response, by altering the RIG-I-Trim25-Keap1-NRF2 complex, leading to reactive oxygen species (ROS) accumulation and BMSC damage. Genetic inhibition of RIG-I sustained NRF2 protein levels and reduced ROS levels in ATRA-treated BMSCs, thus preserving their clonogenicity, bone-forming ability, and stromal niche function in supporting HSC engraftment in mice. More importantly, RIG-I inhibition recovered the ATRA-treated stromal niche function, to enhance HSC engraftment and emergency myelopoiesis for innate immunity against the bacterium Listeria monocytogenes during transplantation. Overall, we identified a non-canonical role of RIG-I in the regulation of the stromal niche for HSC transplantation.

Cellular retinol binding protein-1 inhibits cancer stemness via upregulating WIF1 to suppress Wnt/β-catenin pathway in hepatocellular carcinoma

Background

CRBP-1, a cytosolic chaperone of vitamin A, is identified in a serious number of cancers; however, its biological role in hepatocellular carcinoma (HCC) needs to be further explored. The aim of our present study is to explore the roles and mechanisms of CRBP-1 in regulating liver cancer by using in vitro and in vivo biology approaches.

Methods

The expression level of CRBP-1 was detected using immunohistochemistry in HCC and matching adjacent non-tumorous liver tissues. Following established stable CRBP-1 overexpressed HCC cell lines, the cell growth and tumorigenicity were investigated both in vitro and in vivo. Intracellular retinoic acid was quantified by ELISA. The relationship between CRBP-1 and WIF1 was validated by using dual luciferase and ChIP analyses.

Results

The low expression of CRBP-1 was observed in HCC tissues compared to the normal liver tissues, while high CRBP-1 expression correlated with clinicopathological characteristics and increased overall survival in HCC patients. Overexpression of CRBP-1 significantly inhibited cell growth and tumorigenicity both in vitro and in vivo. Moreover, overexpression of CRBP-1 suppressed tumorsphere formation and cancer stemness related genes expression in HCC. Mechanically, CRBP-1 inhibited Wnt/β-catenin signaling pathway to suppress cancer cell stemness of HCC. Furthermore, our results revealed that CRBP-1 could increase the intracellular levels of retinoic acid, which induced the activation of RARs/RXRs leading to the transcriptional expression of WIF1, a secreted antagonist of the Wnt/β-catenin signaling pathway, by physically interacting with the region on WIF1 promoter.

Conclusion

Our findings reveal that CRBP-1 is a crucial player in the initiation and progression of HCC, which provide a novel independent prognostic biomarker and therapeutic target for the diagnosis and treatment of HCC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08967-2.

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.

Photodegradation of Bexarotene and Its Implication for Cytotoxicity

A detailed understanding of the stability of an active pharmaceutical ingredient and a pharmaceutical dosage form is essential for the drug-development process and for safe and effective use of medicines. Photostability testing as an inherent part of stability studies provides valuable knowledge on degradation pathways and structures of products generated under UV irradiation. Photostability is particularly important for topically administered drugs, as they are more exposed to UV radiation. Bexarotene is a more recent third-generation retinoid approved by the U.S. Food and Drug Administration and the European Medicines Agency as a topically applied anticancer agent. The present study aimed to assess bexarotene photostability, including the presence of UV filters, which have been permitted to be used in cosmetic products in Europe and the USA. The bexarotene photostability testing was performed in ethanol solutions and in formulations applied on PMMA plates. The UPLC-MS/MS technique was used to determine the tested substance. The presence of photocatalysts such as TiO₂ or ZnO, as well as the organic UV filters avobenzone, benzophenone-3, meradimate, and homosalate, could contribute to degradation of bexarotene under UV irradiation. Four photocatalytic degradation products of bexarotene were identified for the first time. The antiproliferative properties of the degradation products of bexarotene were assessed by MTT assay on a panel of human adherent cancer cells, and concentration-dependent growth inhibition was evidenced on all tested cell lines. The cytotoxicity of the formed products after 4 h of UV irradiation was significantly higher than that of the parent compound (p < 0.05). Furthermore non-cancerous murine fibroblasts exhibited marked concentration-dependent inhibition by bexarotene, while the degradation products elicited more pronounced antiproliferative action only at the highest applied concentration.

Reducing FASN expression sensitizes acute myeloid leukemia cells to differentiation therapy

Fatty acid synthase (FASN) is the only human lipogenic enzyme available for de novo fatty acid synthesis and is often highly expressed in cancer cells. We found that FASN mRNA levels were significantly higher in acute myeloid leukemia (AML) patients than in healthy granulocytes or CD34⁺ hematopoietic progenitors. Accordingly, FASN levels decreased during all-trans retinoic acid (ATRA)-mediated granulocytic differentiation of acute promyelocytic leukemia (APL) cells, partially via autophagic degradation. Furthermore, our data suggest that inhibition of FASN expression levels using RNAi or (-)-epigallocatechin-3-gallate (EGCG) accelerated the differentiation of APL cell lines and significantly re-sensitized ATRA refractory non-APL AML cells. FASN reduction promoted translocation of transcription factor EB (TFEB) to the nucleus, paralleled by activation of CLEAR network genes and lysosomal biogenesis. Together, our data demonstrate that inhibition of FASN expression in combination with ATRA treatment facilitates granulocytic differentiation of APL cells and may extend differentiation therapy to non-APL AML cells.

All-trans retinoic acid overcomes solid tumor radioresistance by inducing inflammatory macrophages

Radiotherapy (RT) is an important anti-cancer treatment modality that activates innate and adaptive immune responses. When all-trans retinoic acid (RA) was administered with radiation, we observed superior antitumor responses compared to ionizing radiation (IR) alone or RA alone. The superior antitumor effects of combination treatment were accompanied by a dramatic increase of TNF-α- and inducible nitric oxide synthase (iNOS)-producing inflammatory macrophages in local and distal non-irradiated (distal) tumors. Inflammatory macrophages are essential for the therapeutic efficacy of combination treatment by inducing effector T cell infiltration and enhancing the effector T cell to regulatory T cell ratio in local and distal tumors. T cells and T cell-derived IFN-γ are crucial for increasing inflammatory macrophage levels in IR and RA treated tumors. Notably, whereas CD8⁺ T cells are required for the antitumor response to IR, CD4⁺ T cells are required for the effectiveness of the IR and RA combination. Combination treatment with RA enhanced the abscopal response when radiation and PD-L1 blockade were used together. The synergistic positive feedback loop of inflammatory macrophages and adaptive immunity is required for the antitumor efficacy of IR plus RA combination treatment. Our findings provide a translational and relatively nontoxic strategy for enhancing the local and systemic antitumor effects of IR.

Mechanistic aspects of carotenoid health benefits - where are we now?

Dietary intake and tissue levels of carotenoids have been associated with a reduced risk of several chronic diseases, including cardiovascular diseases, type 2 diabetes, obesity, brain-related diseases and some types of cancer. However, intervention trials with isolated carotenoid supplements have mostly failed to confirm the postulated health benefits. It has thereby been speculated that dosing, matrix and synergistic effects, as well as underlying health and the individual nutritional status plus genetic background do play a role. It appears that our knowledge on carotenoid-mediated health benefits may still be incomplete, as the underlying mechanisms of action are poorly understood in relation to human relevance. Antioxidant mechanisms - direct or via transcription factors such as NRF2 and NF-κB - and activation of nuclear hormone receptor pathways such as of RAR, RXR or also PPARs, via carotenoid metabolites, are the basic principles which we try to connect with carotenoid-transmitted health benefits as exemplified with described common diseases including obesity/diabetes and cancer. Depending on the targeted diseases, single or multiple mechanisms of actions may play a role. In this review and position paper, we try to highlight our present knowledge on carotenoid metabolism and mechanisms translatable into health benefits related to several chronic diseases.

Vitamin A Update: Forms, Sources, Kinetics, Detection, Function, Deficiency, Therapeutic Use and Toxicity

Vitamin A is a group of vital micronutrients widely present in the human diet. Animal-based products are a rich source of the retinyl ester form of the vitamin, while vegetables and fruits contain carotenoids, most of which are provitamin A. Vitamin A plays a key role in the correct functioning of multiple physiological functions. The human organism can metabolize natural forms of vitamin A and provitamin A into biologically active forms (retinol, retinal, retinoic acid), which interact with multiple molecular targets, including nuclear receptors, opsin in the retina and, according to the latest research, also some enzymes. In this review, we aim to provide a complex view on the present knowledge about vitamin A ranging from its sources through its physiological functions to consequences of its deficiency and metabolic fate up to possible pharmacological administration and potential toxicity. Current analytical methods used for its detection in real samples are included as well.

Impact of RARα and miR-138 on retinoblastoma etoposide resistance

BACKGROUND

Retinoblastoma (RB) is the most common childhood eye cancer. Chemotherapeutic drugs such as etoposide used in RB treatment often cause massive side effects and acquired drug resistances. Dysregulated genes and miRNAs have a large impact on cancer progression and development of chemotherapy resistances.

OBJECTIVE

This study was designed to investigate the involvement of retinoic acid receptor alpha (RARα) in RB progression and chemoresistance as well as the impact of miR-138, a potential RARα regulating miRNA.

METHODS

RARα and miR-138 expression in etoposide resistant RB cell lines and chemotherapy treated patient tumors compared to non-treated tumors was revealed by Real-Time PCR. Overexpression approaches were performed to analyze the effects of RARα on RB cell viability, apoptosis, proliferation and tumorigenesis. Besides, we addressed the effect of miR-138 overexpression on RB cell chemotherapy resistance.

RESULTS

A binding between miR-138 and RARα was shown by dual luciferase reporter gene assay. The study presented revealed that RARα is downregulated in etoposide resistant RB cells, while miR-138 is endogenously upregulated. Opposing RARα and miR-138 expression levels were detectable in chemotherapy pre-treated compared to non-treated RB tumor specimen. Overexpression of RARα increases apoptosis levels and reduces tumor cell growth of aggressive etoposide resistant RB cells in vitro and in vivo. Overexpression of miR-138 in chemo-sensitive RB cell lines partly enhances cell viability after etoposide treatment.

CONCLUSIONS

Our findings show that RARα acts as a tumor suppressor in retinoblastoma and is downregulated upon etoposide resistance in RB cells. Thus, RARα may contribute to the development and progression of RB chemo-resistance.

Retinoic acid stimulates transcription of the rat SHARP-2 gene via multiple pathways

Members of the enhancer of split- and hairy-related protein (SHARP) family, SHARP-1 and SHARP-2, are basic helix-loop-helix transcriptional repressors and belong to the clock genes. In this study, an effect of retinoic acid (RA) on the SHARP family gene expression in the differentiated cells was examined. RA rapidly and temporarily induced the SHARP-2 mRNA expression in hepatic H4IIE cells. Then, whether the SHARP-2 mRNA expression is altered by dexamethasone (Dex), insulin, and the combination of RA and Dex or RA and insulin was examined. Dex had different effects on the expression of SHARP-2 mRNA in the presence or absence of RA. Then, the molecular mechanisms were investigated using inhibitors of various signaling molecules. The RA-induction of SHARP-2 mRNA level was mainly inhibited by LY294002, staurosporine, and actinomycin D, respectively. Finally, whether RA acts on the transcriptional regulatory region of the SHARP-2 gene was analyzed using luciferase reporter gene assay. At least two RA-responsive regions were mapped at the nucleotide sequences between -3,700 and -1,600 of the SHARP-2 gene. In addition, this effect was dependent on the retinoic acid receptor and retinoid X receptor. Thus, we conclude that RA stimulated transcription of the SHARP-2 gene via multiple pathways.

Systemic acitretin in the management of periocular squamous cell carcinoma

We report a case of periocular squamous cell carcinoma invading the anterior orbit that significantly reduced in size and regressed from invasive to in situ following treatment with oral acitretin, a second-generation retinoid. The residual in situ disease was then successfully treated with cryotherapy and the patient remains in remission 12 months following cessation of systemic acitretin.

Endogenous and combination retinoids are active in myelomonocytic leukemias

Retinoid therapy transformed response and survival outcomes in acute promyelocytic leukemia (APL) but has demonstrated only modest activity in non-APL forms of acute myeloid leukemia (AML). The presence of natural retinoids in vivo could influence the efficacy of pharmacologic agonists and antagonists. We found that natural RXRA ligands, but not RARA ligands, were present in murine MLL-AF9-derived myelomonocytic leukemias in vivo and that the concurrent presence of receptors and ligands acted as tumor suppressors. Pharmacologic retinoid responses could be optimized by concurrent targeting of RXR ligands (e.g., bexarotene) and RARA ligands (e.g., all-trans retinoic acid), which induced either leukemic maturation or apoptosis depending on cell culture conditions. Co-repressor release from the RARA:RXRA heterodimer occurred with RARA activation, but not RXRA activation, providing an explanation for the combination synergy. Combination synergy could be replicated in additional, but not all, AML cell lines and primary samples, and was associated with improved survival in vivo, although tolerability of bexarotene administration in mice remained an issue. These data provide insight into the basal presence of natural retinoids in leukemias in vivo and a potential strategy for clinical retinoid combination regimens in leukemias beyond APL.

Restoration of ceramide de novo synthesis by the synthetic retinoid ST1926 as it induces adult T-cell leukemia cell death

Ceramide (Cer) is a bioactive cellular lipid with compartmentalized and tightly regulated levels. Distinct metabolic pathways lead to the generation of Cer species with distinguishable roles in oncogenesis. Deregulation of Cer pathways has emerged as an important mechanism for acquired chemotherapeutic resistance. Adult T-cell leukemia (ATL) cells are defective in Cer synthesis. ATL is an aggressive neoplasm that develops following infection with human T-cell lymphotropic virus-1 (HTLV-1) where the viral oncogene Tax contributes to the pathogenesis of the disease. ATL cells, resistant to all-trans-retinoic acid, are sensitive to pharmacologically achievable concentrations of the synthetic retinoid ST1926. We studied the effects of ST1926 on Cer pathways in ATL cells. ST1926 treatment resulted in early Tax oncoprotein degradation in HTLV-1-treated cells. ST1926 induced cell death and a dose- and time-dependent accumulation of Cer in malignant T cells. The kinetics and degree of Cer production showed an early response upon ST1926 treatment. ST1926 enhanced de novo Cer synthesis via activation of ceramide synthase CerS(s) without inhibiting dihydroceramide desaturase, thereby accumulating Cer rather than the less bioactive dihydroceramide. Using labeling experiments with the unnatural 17-carbon sphinganine and measuring the generated Cer species, we showed that ST1926 preferentially induces the activities of a distinct set of CerS(s). We detected a delay in cell death response and interruption of Cer generation in response to ST1926 in Molt-4 cells overexpressing Bcl-2. These results highlight the potential role of ST1926 in inducing Cer levels, thus lowering the threshold for cell death in ATL cells.

Dietary Antioxidant Vitamins and Minerals and Breast Cancer Risk: Prospective Results from the SUN Cohort

There is growing interest in natural antioxidants and their potential effects on breast cancer (BC). Epidemiological evidence, however, is inconsistent. We prospectively evaluated the association between dietary intake of vitamins A, C, and E, selenium, and zinc and BC among 9983 female participants from the SUN Project, a Mediterranean cohort of university graduates. Participants completed a food frequency questionnaire at baseline, and biennial follow-up information about incident BC diagnosis was collected. Cases were ascertained through revision of medical charts and consultation of the National Death Index. Cox proportional hazards models were used to estimate multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CI). During an average follow-up of 11.3 years, 107 incident BC cases were confirmed. The multivariable HRs (95% CI) for BC comparing extreme tertiles of energy-adjusted dietary intakes were 1.07 (0.64–1.77; P_trend = 0.673) for vitamin A, 1.00 (0.58–1.71; P_trend = 0.846) for vitamin C, 0.92 (0.55–1.54; P_trend = 0.728) for vitamin E, 1.37 (0.85–2.20; P_trend = 0.135) for selenium, and 1.01 (0.61–1.69; P_trend = 0.939) for zinc. Stratified analyses showed an inverse association between vitamin E intake and postmenopausal BC (HR_{T3 vs. T1} = 0.35; 95% CI, 0.14–0.86; P_trend = 0.027). Our results did not suggest significant protective associations between dietary vitamins A, C, and E, selenium, or zinc and BC risk.

The Potential of Cryptophyte Algae in Biomedical and Pharmaceutical Applications

Microalgae produce a variety of bioactive components that provide benefits to human and animal health. Cryptophytes are one of the major groups of microalgae, with more than 20 genera comprised of 200 species. Recently, cryptophytes have attracted scientific attention because of their characteristics and biotechnological potential. For example, they are rich in a number of chemical compounds, such as fatty acids, carotenoids, phycobiliproteins and polysaccharides, which are mainly used for food, medicine, cosmetics and pharmaceuticals. This paper provides a review of studies that assess protective algal compounds and introduce cryptophytes as a remarkable source of bioactive components that may be usable in biomedical and pharmaceutical sciences.

Mitochondrial GRIM-19 deficiency facilitates gastric cancer metastasis through oncogenic ROS-NRF2-HO-1 axis via a NRF2-HO-1 loop

BACKGROUND

NRF2, a prime target of cellular defense against oxidative stress, has shown a dark side profile in cancer progression. GRIM-19, an essential subunit of the mitochondrial MRC complex I, was recently identified as a suppressive role in tumorigenesis of human gastric cancer (GC). However, little information is available on the role of GRIM-19 and its cross-talk with NRF2 in GC metastasis.

METHODS

Online GC database was used to investigate DNA methylation and survival outcomes of GRIM-19. CRISPR/Cas9 lentivirus-mediated gene editing, metastasis mice models and pharmacological intervention were applied to investigate the role of GRIM-19 deficiency in GC metastasis. Quantitative RT-PCR, FACS, Western blot, IHC, IF and reporter gene assay were performed to explore underlying mechanisms.

RESULTS

Low GRIM-19 is correlated with poor survival outcome of GC patients while DNA hypermethylation is associated with GRIM-19 downregulation. GRIM-19 deficiency facilitates GC metastasis and triggers aberrant oxidative stress as well as ROS-dependent NRF2-HO-1 activation. Experimental interventions of specific ROS, NRF2 or HO-1 inhibitor significantly abrogate GRIM-19 deficiency-driven GC metastasis in vitro and in vivo. Moreover, HO-1 inhibition not only reverses GRIM-19 deficiency-driven NRF2 activation, but also feedback blocks NRF2 activator-induced NRF2 signaling, resulting in decreased metastasis-associated genes.

CONCLUSIONS

Our data suggest that GRIM-19 deficiency accelerates GC metastasis through the oncogenic ROS-NRF2-HO-1 axis via a positive-feedback NRF2-HO-1 loop. Therefore, this study not only offers novel insights into the role of oncogenic NRF2 in tumor progression, but also provides new strategies to alleviate the dark side of NRF2 by targeting HO-1.

Current status and future directions of hepatocellular carcinoma-targeted nanoparticles and nanomedicine

INTRODUCTION

Hepatocellular carcinoma (HCC) is a major health problem worldwide. Conventional therapies covering either chemotherapy or combination therapy still have sub-optimal responses with significant adverse effects and toxicity. Moreover, tumor cells usually acquire resistance quickly for traditional approaches, limiting their use in HCC. Interest in nanomedicine due to minimal systemic toxicity and a high degree of target-specific drug-delivery have pulled the attention of health scientists in this area of therapeutics.

AREA COVERED

The review covers the incidence and epidemiology of HCC, proposed molecular drug targets, mechanistic approach and emergence of nanomedicines including nanoparticles, lipidic nanoparticles, vesicular-based nanocarrier, virus-like particles with momentous therapeutic aspects including biocompatibility, and toxicity of nanocarriers along with conclusions and future perspective, with an efficient approach to safely cross physiological barriers to reach the target site for treating liver cancer.

EXPERT OPINION

Remarkable outcomes have recently been observed for the therapeutic efficacy of nanocarriers with respect to a specific drug target against the treatment of HCC by existing under trial drugs.

LSD1: more than demethylation of histone lysine residues

Lysine-specific histone demethylase 1 (LSD1) represents the first example of an identified nuclear protein with histone demethylase activity. In particular, it plays a special role in the epigenetic regulation of gene expression, as it removes methyl groups from mono- and dimethylated lysine 4 and/or lysine 9 on histone H3 (H3K4me1/2 and H3K9me1/2), behaving as a repressor or activator of gene expression, respectively. Moreover, it has been recently found to demethylate monomethylated and dimethylated lysine 20 in histone H4 and to contribute to the balance of several other methylated lysine residues in histone H3 (i.e., H3K27, H3K36, and H3K79). Furthermore, in recent years, a plethora of nonhistone proteins have been detected as targets of LSD1 activity, suggesting that this demethylase is a fundamental player in the regulation of multiple pathways triggered in several cellular processes, including cancer progression. In this review, we analyze the molecular mechanism by which LSD1 displays its dual effect on gene expression (related to the specific lysine target), placing final emphasis on the use of pharmacological inhibitors of its activity in future clinical studies to fight cancer.

Further research into the complex structure and behavior of an enzyme involved in gene regulation could improve future cancer therapies. The modification of chromosomal proteins known as histones can fundamentally change gene expression and influence the progression of diseases such as cancer. Bruno Perillo at the Italian National Research Council, Naples, Italy, and co-workers reviewed understanding of the structurally complex enzyme lysine-specific histone demethylase 1 A (LSD1), which interacts with multiple targets including histones. LSD1 removes methyl groups from histones, fine-tuning gene expression and influencing protein activity. The overexpression of LSD1 is linked to cancer development, particularly in aggressive cancers, and inhibiting LSD1 has shown promise in slowing progression and cancer spread. The researchers call for further research into the complexities of LSD1 activity, both in cancers and normal cell function.

Effect of vitamin A as a neoadjuvant agent in chemotherapy and photodynamic therapy of Rhabdomyosarcoma cells

Combinational therapy is among the most used treatment modality's to increase cancer treatment efficacy. It may also reduce side effects, treatment time, and development of drug resistance. The effects of different analogues of vitamin A (VA) as neoadjuvant agent were observed in this study with chemotherapeutic drugs (doxorubicin and methotrexate) and photodynamic therapy (PDT) using 5-ALA and Photogem as photosensitizers in RD cells. The uptake time of photosensitizer was optimized by means of spectrophotometric measurements. Diode laser (λ = 635 nm ± 1 nm) was used as an illumination source for PDT. Responses of administered drugs were assessed by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. VA and its analogues exert prophylactic and therapeutic effects. Protective or antagonistic effects (CI > 1) were observed in each of the case. These results propose that the use of VA as a neoadjuvant agent in combinational therapeutic modalities may reduce the efficacy of cancer treatment protocols as well as the existing side effects. Thus, VA is not the successful drug for combinational therapies and under treatment cancer patients should try to avoid its use with oxidative stress induction therapies (e.g. PDT, Radiotherapy, chemotherapy).

Association study between genetic variants in retinol metabolism pathway genes and prostate cancer risk

Background

Evidence suggests that serum retinol level is associated with prostate cancer risk, but the association between genetic variants in the retinol metabolism pathway genes and prostate cancer risk remains unclarified.

Methods

Single‐nucleotide polymorphisms (SNPs) in 31 genes in the retinol metabolism pathway were genotyped to evaluate the association with prostate cancer risk in 4,662 cases and 3,114 controls from the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial. The gene expression analysis was evaluated using data from the Gene Expression Omnibus (GEO) datasets and the Cancer Genome Atlas (TCGA) database. Data from the Genotype‐Tissue Expression (GTEx) project dataset were utilized to perform the expression quantitative trait loci (eQTL) analysis.

Results

Two SNPs were significantly associated with prostate cancer risk [rs1330286 in ALDH1A1: odds ratio (OR) = 0.88, 95% confidence interval (CI) = 0.83‐0.94, p = 2.45 × 10⁻⁴; rs4646653 in ALDH1A3: OR = 1.17, 95% CI =1.07‐1.27, p = 4.33 × 10⁻⁴]. Moreover, the mRNA level of ALDH1A3 was significantly higher in prostate cancer tissues than in normal tissues in both TCGA datasets and GEO datasets (p = 1.63 × 10⁻¹² and p = 4.33 × 10⁻², respectively). rs1330286 was an eQTL of ALDH1A1 (P = 2.90 × 10⁻³).

Conclusion

Our findings highlight that genetic variants in retinol metabolism pathway genes are associated with prostate cancer risk.

Natural and synthetic retinoids in preclinical colorectal cancer models

Colorectal cancer (CRC) remains a leading cause of cancer-related morbidity and mortality worldwide. Although targeted therapy in combination with chemotherapy in CRC prolongs the overall survival of patients with metastatic disease, acquired resistance and relapse hinder their clinical benefits. Moreover, patients with some specific genetic profile are unlikely to benefit from targeted therapy, suggesting the need for safe and effective treatment strategies. Retinoids, comprising of natural and synthetic analogs, are a class of chemical compounds that regulate cellular proliferation, differentiation, and cell death. Retinoids have been used in the clinic for several leukemias and solid tumors, either as single agents or in combination therapy. Furthermore, retinoids have shown potent chemotherapeutic and chemopreventive properties in different cancer models, including CRC. In this review, we summarize the major preclinical findings in CRC in which natural and synthetic retinoids showed promising antitumor activities and stress on the proposed mechanisms of action. Understanding of the retinoids' antitumor mechanisms would provide insights to support and warrant their development in the management of CRC.

Prospects of tangeretin as a modulator of cancer targets/pathways

To date, cancer is the second leading cause of death worldwide after cardiac arrest. A large number of synthetic drugs are available for the treatment of different types of cancer; however, a major problem associated with these drugs is its toxicity towards the normal cells. To overcome these problems, researchers explore plants derived phytochemicals because of their pleiotropic action and least toxicity towards the normal cells. Tangeretin is a polymethoxylated flavone found extensively in citrus fruits and has shown potent anti-cancer activity in different types of cancer cells. Hence, this review examines the anti-cancer activity of tangeretin via different molecular targets/pathways. Tangeretin induces apoptosis via intrinsic as well as extrinsic pathways and arrest the cell cycle. It also suppresses cell proliferation by modulating PI3K/AKT/mTOR, Notch, and MAPK signalling pathways. Besides, it induces autophagic cell death, suppresses migration, invasion, and angiogenesis. Further, the role of tangeretin in multi-drug resistance and combination therapy, different biological sources of tangeretin, its derivatives, and pharmacokinetics profile and toxicity studies are also discussed. Towards the end, the challenges associated with tangeretin usage as potential anti-cancer phytochemicals have also been discussed. Tangeretin, like a pandora's box, needs to be explored further, and more research is warranted to improve its usefulness for better human health.

Cellular retinol binding protein 1 transfection reduces proliferation and AKT-related gene expression in H460 non-small lung cancer cells

In recent years, new treatments with novel action mechanisms have been explored for advanced non-small cell lung cancer (NSCLC). Retinoids promote cancer cell differentiation and death and their trafficking and action is mediated from specific cytoplasmic and nuclear receptors, respectively. The purpose of this study was to investigate the effect of Cellular retinol binding protein-1 (CRBP-1) transfection in H460 human NSCLC cell line, normally not expressing CRBP-1. H460 cells were transfected by using a vector pTargeT Mammalian expression system carrying the whole sequence of CRBP-1 gene. For proliferation and apoptosis studies, cells were treated with different concentrations of all-trans Retinoic Acid (atRA) and retinol. AKT-related gene expression was analyzed by using western blot and Signosis array and results analysed by one-way analysis of variance (ANOVA) or by t-student test. CRBP-1⁺ showed reduced proliferation and viability in basal condition and after atRA treatment when compared to empty-transfected H460 cells. Reduced proliferation in CRBP-1⁺ H460 cells associated to the down-regulation of pAKT/pERK/pEGFR-related genes. In particular, gene array documented the down-regulation of AKT and Stat-3-related genes, including M-Tor, Akt1, Akt2, Akt3, Foxo1, p27, Jun. Restoration of CRBP-1 expression in H460 cells reduced proliferation and viability in both basal condition and after atRA treatment, likely by down-regulating AKT-related gene level. Further studies are needed to better clarify how those CRBP-1-related intracellular pathways contribute to counteract NSCLC progression in order to suggest a potential tool to improve efficacy of retinoid anti lung cancer adjuvant therapy.

5-aminolevulinic acid photodynamic therapy enhance the effect of acitretin on squamous cell carcinoma cells: An in vitro study

Squamous cell carcinoma (SCC) remains the second most common nonmelanoma skin cancer (NMSC) worldwide. Both acitretin and 5-Aminolevulinic acid mediated photodynamic therapy (ALA-PDT) have validated effect on SCC. However, the effects of both treatmens remain limited, and there has been no report concerning the potential synergistic effect of both treatments for SCC.

OBJECTIVE

To investigate the cytotoxic effect of acitretin on SCL-1 cells, and whether ALA-PDT enhances this effect.

METHODS

CCK-8 and trypan blue exclusion array were used to detect the cell cytotoxicity after acitretin treatment with different concentrations (1.6 × 10^-4mg/mL, 1.6 × 10^-3 mg/mL, 1.6 × 10^-2mg/mL and 1.6 × 10^-1mg/mL) for 24 h, 48 h and 72 h. Flow cytometry and trypan blue exclusion assay were used to detect the apoptosis and viability of SCL-1 cells after treated with acitretin, ALA-PDT and ALA-PDT immediately followed by acitretin. Independent sample t test was used to analyze the different incubation time of acitretin and acitretin combined with ALA-PDT on SCL-1 cells. Bonferroni Test One-way Anova method was used to analyze the effect of different treatment on the SCL-1 cells.

RESULTS

A significant cytotoxic effect was observed after acitretin treatment, in an acitretin concentration-dependent manner within the range of 1.6 × 10^-4mg/mL to 1.6 × 10^-1mg/mL and an acitretin incubation time-dependent manner within 24 h-72 h. The total apoptosis rate and dead cells rate in group of ALA-PDT combined with acitretin were both significantly higher than that of acitretin, ALA-PDT group. A stronger apoptotic and cytotoxic effect detected 24 h after treated with acitretin than that of 12 h was observed in this study.

CONCLUSION

Acitretin has a cytotoxic effect on SCL-1 cells, and ALA-PDT treatment enhances the the cytotoxic effect of acitretin.

All-Trans Retinoic Acid Exerts Neuroprotective Effects in Amyotrophic Lateral Sclerosis-Like Tg (SOD1*G93A)1Gur Mice

All-trans retinoic acid (ATRA), a ligand of retinoic acid receptors, could regulate various biological processes by activating retinoic acid signals. Recent studies suggested that ATRA displays multiple neuroprotective effects and thereby alleviates the disease progression in a variety of neurological diseases. Our previous studies found that the impaired retinoic acid signal decreased ALDH1A2, an essential synthetase of ATRA, in the spinal cord of ALS mice. Here, we evaluated the neuroprotective and neurorestorative effects of ATRA in a SOD1-G93A transgenic mice model of ALS. We administrated ATRA(3 mg/kg) daily from the onset stage to the progression stage for 5 weeks. Behavioral tests showed that ATRA improved the forelimb grip strength in ALS mice and may slow the disease progression, but not the body weight. ATRA could completely reverse the impaired retinoic acid receptor alpha (RARα) signal in the spinal cord of ALS mice. This effect was accompanied by enhancing the degradation of misfolded proteins via the ubiquitin-proteasome system, regulating the oxidative stress, inhibiting the astrocyte activation, and promoting the neurotrophic signal recovery. Our findings are the first to indicate that the damaged retinoic acid signal is involved in the pathogenesis of ALS, and ATRA could induce the functional neuroprotection via repairing the damaged retinoic acid signal.

Reconfiguring Nature's Cholesterol Accepting Lipoproteins as Nanoparticle Platforms for Transport and Delivery of Therapeutic and Imaging Agents

Apolipoproteins are critical structural and functional components of lipoproteins, which are large supramolecular assemblies composed predominantly of lipids and proteins, and other biomolecules such as nucleic acids. A signature feature of apolipoproteins is the preponderance of amphipathic α-helical motifs that dictate their ability to make extensive non-covalent inter- or intra-molecular helix-helix interactions in lipid-free states or helix-lipid interactions with hydrophobic biomolecules in lipid-associated states. This review focuses on the latter ability of apolipoproteins, which has been capitalized on to reconstitute synthetic nanoscale binary/ternary lipoprotein complexes composed of apolipoproteins/peptides and lipids that mimic native high-density lipoproteins (HDLs) with the goal to transport drugs. It traces the historical development of our understanding of these nanostructures and how the cholesterol accepting property of HDL has been reconfigured to develop them as drug-loading platforms. The review provides the structural perspective of these platforms with different types of apolipoproteins and an overview of their synthesis. It also examines the cargo that have been loaded into the core for therapeutic and imaging purposes. Finally, it lays out the merits and challenges associated with apolipoprotein-based nanostructures with a future perspective calling for a need to develop "zip-code"-based delivery for therapeutic and diagnostic applications.

Association between plasma retinol levels and the risk of all-cause mortality in general hypertensive patients: A nested case-control study

To evaluate the association between plasma retinol levels with all-cause mortality and investigate the possible effect modifiers in general hypertensive patients with no previous cardiovascular disease (CVD). This case-control study was nested in the China Stroke Primary Prevention Trial (CSPPT), a randomized, double-blind, controlled trial conducted in 32 communities in Anhui and Jiangsu provinces in China. The current study included 617 cases of all-cause mortality and 617 controls matched on age (≤1 year), sex, treatment group, and study site. All-cause mortality was the main outcome in this analysis, which included death due to any reason. The median follow-up duration was 4.5 years. Overall, there was a U-shaped relation of plasma retinol with all-cause mortality. In the threshold effect analysis, the risk of all-cause mortality significantly decreased with the increase in plasma retinol (per 10 μg/dL increments: OR, 0.73; 95% CI: 0.61-0.87) in participants with plasma retinol <58.3 μg/dL and increased with the increase in plasma retinol (per 10 μg/dL increments: OR, 1.08; 95% CI: 1.01-1.16) in those with plasma retinol ≥58.3 μg/L. In participants with plasma retinol <58.3 μg/dL, a stronger inverse association was observed in those with higher time-averaged SBP (≥140 vs <140 mm Hg; P-interaction = .034), or higher vitamin E levels (≥11.5 [quartile 4]; vs <11.5 μg/mL; P-interaction = .013). The present study demonstrated that there was a U-shaped relationship of plasma retinol levels with the risk of all-cause mortality in general hypertensive patients, with a turning point around 58.3 μg/dL.

Retinoic Acid Receptors in Acute Myeloid Leukemia Therapy

Retinoic acid (RA) signaling pathways regulate fundamental biological processes, such as cell proliferation, development, differentiation, and apoptosis. Retinoid receptors (RARs and RXRs) are ligand-dependent transcription factors. All-trans retinoic acid (ATRA) is the principal endogenous ligand for the retinoic acid receptor alpha (RARA) and is produced by the enzymatic oxidation of dietary vitamin A, whose deficiency is associated with several pathological conditions. Differentiation therapy using ATRA revolutionized the outcome of acute promyelocytic leukemia (APL), although attempts to replicate these results in other cancer types have been met with more modest results. A better knowledge of RA signaling in different leukemia contexts is required to improve initial designs. Here, we will review the RA signaling pathway in normal and malignant hematopoiesis, and will discuss the advantages and the limitations related to retinoid therapy in acute myeloid leukemia.

Regulation of RXR-RAR Heterodimers by RXR- and RAR-Specific Ligands and Their Combinations

The three subtypes (α, β, and γ) of the retinoic acid receptor (RAR) are ligand-dependent transcription factors that mediate retinoic acid signaling by forming heterodimers with the retinoid X receptor (RXR). Heterodimers are functional units that bind ligands (retinoids), transcriptional co-regulators and DNA, to regulate gene networks controlling cell growth, differentiation, and death. Using biochemical, crystallographic, and cellular approaches, we have set out to explore the spectrum of possibilities to regulate RXR-RAR heterodimer-dependent transcription through various pharmacological classes of RAR- and RXR- specific ligands, alone or in combination. We reveal the molecular details by which these compounds direct specificity and functionality of RXR-RAR heterodimers. Among these ligands, we have reevaluated and improved the molecular and structural definition of compounds CD2665, Ro41-5253, LE135, or LG100754, highlighting novel functional features of these molecules. Our analysis reveals a model of RXR-RAR heterodimer action in which each subunit retains its intrinsic properties in terms of ligand and co-regulator binding. However, their interplay upon the combined action of RAR- and RXR-ligands allows for the fine tuning of heterodimer activity. It also stresses the importance of accurate ligand characterization to use synthetic selective retinoids appropriately and avoid data misinterpretations.