Evaluation of the actions and interactions of retinoic acid and epidermal growth factor on transformed urothelial cells in culture: implications for the use of retinoid therapy in the treatment of bladder cancer patients

Insights into vitamin A in bladder cancer, lack of attention to gut microbiota?

Vitamin A has long been associated with bladder cancer, and many exogenous vitamin A supplements, vitamin A derivatives, and synthetic drugs have been investigated over the years. However, the effectiveness of these strategies in clinical practice has not met expectations, and they have not been widely adopted. Recent medical research on intestinal flora has revealed that bladder cancer patients exhibit reduced serum vitamin A levels and an imbalance of gut microbiota. In light of the close relationship between gut microbiota and vitamin A, one can speculate that a complex regulatory mechanism exists between the two in the development and occurrence of bladder cancer. As such, further exploration of their interaction in bladder cancer may help guide the use of vitamin A for preventive purposes. During the course of this review, attention is paid to the influence of intestinal microbiota on the vitamin A metabolism and the RA signaling pathway, as well as the mutual promotion relationships between them in the prevention of bladder cancer, In addition, it emphasizes the importance of intestinal microbiota for bladder cancer prevention and treatment.

Retinoic acid signaling and bladder cancer: Epigenetic deregulation, therapy and beyond

Retinoic acid (RA) signaling is a crucial developmental pathway involved in urothelium development, differentiation and regeneration. Deregulation of the RA signaling is highly implicated in several cancers, including bladder cancer, underlying the need to unravel the complete regulatory aspects of the retinoids in bladder tumorigenesis. Given the fact that RA receptors are transcription factors functioning at the chromatin level and act in close cooperation with chromatin modifiers, it is known that retinoids show their efficacy by changing the epigenome. Bladder cancer can be defined as a "disease of chromatin" with mutations identified in the genes involved in chromatin regulation in 80% of the patients. Therefore, a careful examination of the epigenetic backgrounds and the breakdown of the emerging and highly underexplored field of RA dependent regulation of the epigenome is essential to fully understand the retinoid-dependent effects on bladder cancer. With this motivation, in this review, we evaluate the role of RA signaling in bladder cancer with a focus on the regulatory and mutational aspects, emphasizing the deregulatory characteristics in bladder cancer and highlighting the potential treatment opportunities with the RA and derivatives alone or in combination with epigenetic drugs.

Vitamin A and Retinoids in Bladder Cancer Chemoprevention and Treatment: A Narrative Review of Current Evidence, Challenges and Future Prospects

Bladder cancer (BC) is the tenth most common cancer worldwide with a high recurrence rate, morbidity and mortality. Therefore, chemoprevention and improved treatment of BC are of paramount importance. Epidemiological studies suggest that adequate vitamin A intake may be associated with reduced BC risk. In addition, retinoids, natural and synthetic derivatives of vitamin A, are intensively studied in cancer research due to their antioxidant properties and their ability to regulate cell growth, differentiation, and apoptosis. Findings from in vivo and in vitro models of BC show great potential for the use of retinoids in the chemoprevention and treatment of BC. However, translation to the clinical practice is limited. In this narrative review we discuss: (i) vitamin A and retinoid metabolism and retinoic acid signalling, (ii) the pathobiology of BC and the need for chemoprevention, (iii) the epidemiological evidence for the role of dietary vitamin A in BC, (iv) mechanistic insights obtained from in vivo and in vitro models, (v) clinical trials of retinoids and the limitations of retinoid use, (vi) novel systems of retinoid delivery, and (vii) components of retinoid signalling pathways as potential novel therapeutic targets.

Retinoids: novel immunomodulators and tumour-suppressive agents?

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

Retinoids in the prevention of bladder cancer

Superficial bladder cancer has an unpredictable natural history but in many patients it has a tendency for multiple recurrences over many years. Chemoprevention approaches are ideally tested in this type of tumor and may delay or prevent recurrences of superficial bladder cancer or prevent progression to invasive disease. Vitamin A and its derivatives, the retinoids, have been studied in detail in this disease. This article reviews the data on this subject and includes in vitro and in vivo preclinical studies as well as the clinical studies performed in the secondary prevention of this disease.

PSCA expression is regulated by phorbol ester and cell adhesion in the bladder carcinoma cell line RT112

The expression of the surface protein prostate stem cell antigen (PSCA) in prostate carcinoma increases in parallel with the progression of the tumor. In contrast, we have recently shown that PSCA expression is reduced or undetectable in other types of undifferentiated tumors. To elucidate the cellular mechanisms that underlie this complex pattern of expression, we studied regulatory parameters for PSCA expression in the bladder carcinoma cell line RT112 by Northern analysis. PSCA gene expression was stimulated by a culture dish surface that caused aggregation of cells, suggesting that its expression is regulated by mechanisms related to the adhesion of epithelial cells. Phorbol ester markedly stimulated PSCA gene expression in a cycloheximide- and actinomycin-inhibitable manner after a lag phase of 10 h, indicating that transcription of the PSCA gene is regulated by protein kinase C and a newly synthesized protein. In contrast, epidermal growth factor, platelet-derived growth factor (PDGF)-BB, tumor necrosis factor-alpha, interferon-gamma or a slightly lowered pH failed to increase PSCA mRNA levels. Consistent with the variable expression of PSCA in different tumors, our analysis in RT112 cells shows that its expression is controlled by a strongly inducible promoter that is specifically regulated by extracellular signals.

Retinoid signaling in immortalized and carcinoma-derived human uroepithelial cells

This paper investigates the presence and functionality of retinoid signaling pathways in human urinary bladder carcinoma and SV40-immortalized uroepithelial cell lines. Only two of eight cell lines were proliferation-inhibited by 10 microM of either all-trans or 13-cis-retinoic acid. Transactivation of the CAT gene under control of a retinoid-responsive element demonstrated functionality of the signaling pathway in both sensitive cell lines and four of six resistant cell lines. Relative RT-PCR analysis of a panel of retinoid-responsive and inducible genes demonstrated changes in expression levels of all the genes in response to-retinoic acid treatment together with numerous aberrations dysregulations. We conclude that retinoid signaling may be a target for inactivation during tumorigenesis by uncoupling gene expression, proliferation and differentiation. Therefore retinoids are more likely to be effective for chemoprevention than for treatment of bladder carcinomas.

Cellular hyperplasia in rats following continuous intravenous infusion of recombinant human epidermal growth factor

In this study, we determined in vivo morphologic effects of continuous intravenous infusion of recombinant human epidermal growth factor (EGF) in adult Wistar rats. The EGF used consisted of the amino acid residues 1-48 of the human 53-amino-acid EGF molecule, purified from transfected Escherichia coli. Doses of 25, 100, or 250 micrograms/kg body weight were administered using Harvard digital syringe infusion pumps for 4 weeks. At necropsy, the submandibular salivary glands, Harderian glands, liver, kidneys (females only), and ovaries were enlarged and urinary bladders were thickened in 100- and 250-micrograms/kg rats. Numerous tissues of the 100- and 250-micrograms/kg rats contained hyperplastic epithelial cells, and selected organs also had mesenchymal cell proliferation. Epithelial proliferation was most pronounced in the trachea, nasal cavity, nasolacrimal duct, tongue, stomach, small intestine, large intestine, urinary tract, salivary gland ducts, and Harderian gland. Periportal hepatocytes were hypertrophic, correlating with increased liver weight. In addition, mesenchymal cell proliferation was evident in the gastric mucosa lamina propria and in heart valves in 100- and 250-micrograms/kg rats. Increased ovarian weight correlated with increased number and size of corpora lutea and an increased incidence of luteal cysts. Continuous systemic exposure of adult Wistar rats to high doses of EGF resulted in generalized epithelial hyperplasia and tissue-selective mesenchymal proliferation.

Activity of 4-HPR in superficial bladder cancer using DNA flow cytometry as an intermediate endpoint

The ability of the synthetic retinoid N-(4-hydroxyphenyl)retinamide (4-HPR) to affect the outcome of previously resected superficial bladder cancer was investigated in a pilot study using DNA content flow cytometry and conventional cytology as intermediate endpoints. Twelve patients were treated with oral 4-HPR (200 mg daily) and compared with 17 non-randomized, untreated controls. The median interval between transurethral resection and 4-HPR administration was 5.5 months (range 0-36). The median follow-up period was 12 months (range 3-31) in the 4-HPR group and 9 months (range 2-22) in the control group. The proportion of patients with DNA aneuploid stemlines in bladder-washed cells decreased from 7/12 (58%) to 5/11 (45%) in the 4-HPR group, but increased from 7/17 (41%) to 10/17 (59%) in the control group. In patients with stable diploid profiles, mean (+/- SE) S-phase and G2+M-phase fractions decreased in the course of retinoid treatment from basal levels of 15.2 +/- 4.1% to 7.5 +/- 3.3% and 10.3 +/- 2.2% to 5.2 +/- 0.4%, respectively. The same parameters in the control group changed from basal levels of 14.6 +/- 3.4% to 12.4 +/- 2.7% and 9.8 +/- 1.6% to 12.6 +/- 1.6%, respectively. Positive or suspicious cytologic examinations were present in 3/12 (25%) treated cases prior to 4-HPR administration and all subsequently reverted to normal. The same parameter in the control group increased from 4/17 (24%) to 6/17 (35%) during follow-up. Impaired adaptation to darkness was recorded in 4 patients, and transient dermatologic alterations were observed in one-third of the patients, requiring dose reduction in one case.(ABSTRACT TRUNCATED AT 250 WORDS)