Retinoid actions and implications for prevention and therapy of oral cancer

Preventive measures in oral cancer: An overview

Worldwide oral cancer is creating an alarming situation and it's a matter of global concern as it is the 11th most common carcinoma around the globe. After cardiovascular ailments, cancer is the next biggest killer. Approximately 90% of the total oral malignancies are squamous cell carcinomas. The etiological base of oral cancer is tobacco intake, smoking, smokeless tobacco (snuff or chewing tobacco), alcohol and areca nut intake, excessive sunlight exposure, reverse end smoking and Human Papilloma Virus (HPV). The treatment measures for oral cancer are very costly and affordability is low. So, taking preventive measures at the first place itself is of immense importance. Preventive measure is a multidisciplinary approach involving co-ordinated efforts from all the sectors of the society. The preventive measures are categorised into primary, secondary and tertiary measures. Along with the various screening tests employed to detect oral cancer the review focuses on biomarkers, melatonin, tea constituents, polyphenols, chemoprevention, Chios mastic gum extract, Poly (ADP-ribose) Polymerase 1 (PARP1) targeted optical imaging agent, and their role in oral cancer prevention and control. The review gives a brief outline on the preventive measures to be adopted to help prevent oral cancer and improve the quality of life.

Photodynamic therapy: a review and its prospective role in the management of oral potentially malignant disorders

With the unreliability of epithelial dysplasia as a predictor to determine the risk of future malignant development, subjectivity associated in evaluating dysplasia by pathologists and paucity of biomarkers that could accurately predict the progression risks in oral potentially malignant disorders (PMDs), eradication of the lesions appears to be the most desirable approach to minimize the risk of invasive cancer formation. Interventions, such as surgery and chemoprevention, have not shown promising long-term results in the treatment of these lesions, and lack of guidelines and general consensus on their management has incited much anxiety and doubts in both patients and community clinicians. Topical photodynamic therapy (PDT) is a minimally invasive and minimally toxic technique that in recent years has shown great promise in the management of PMDs. In this review, we describe the historical developments in the field of PDT, its basic mechanisms, as well as related clinical studies, and its challenges in the management of oral PMDs. Based on its high efficacy and low side effects, its high patient acceptance/compliance, the simplicity of the procedure and its minimal pretreatment preparation, topical PDT is believed to have potential to play an important role in the management of PMDs, especially of the low-grade dysplasia.

A review of the nonsurgical treatment of oral leukoplakia

The aim of this paper was to assess the nonsurgical treatment of oral leukoplakia (OL). A medline search from 1983 to 2009 was conducted. The topical or systemic nonsurgical treatments or combination of both was reviewed. The primary outcomes of interest were clinical resolution, malignant transformation, follow-up, and recurrence of OL. Studies showed a rate higher than 50% of clinical resolution with photodynamic therapy, beta-carotene, lycopene, or vitamin A. Few studies reported rates of recurrence from 5 to 67% and of malignant transformation from 8 to 23%. There is a lack of randomized clinical trials that assess the effectiveness of nonsurgical treatment of OL. At this time, randomized controlled trials for nonsurgical treatment of OL demonstrate no evidence of effective treatment in preventing malignant transformation and recurrence. It reinforces that even after clinical resolution, OL should be regularly followed.

Three-year follow-up of oral leukoplakia after neodymium:yttrium aluminum garnet (Nd:YAG) laser surgery

Oral leukoplakia is a relatively common lesion with a significant proportion of cases changing into cancer. Since most leukoplakias are asymptomatic, the primary objective of treatment must aim at the prevention of such malignant transformation. The main objectives of the study are to observe (1) the efficacy, safety and acceptability of the neodymium:yttrium aluminum garnet (Nd:YAG) laser in the management of oral leukoplakia; (2) the nature of postoperative complications, if any, associated with laser ablation, and (3) the 3-year prognosis of oral leukoplakia treated with laser. Twenty-eight patients with histologically proven leukoplakia were treated with Nd:YAG laser. From this study, we observed that the patients treated with Nd:YAG laser had only mild to moderate pain, swelling and restricted mouth opening, which peaked between 72 h and 1 week. In a majority of the patients the healing was prolonged, to a maximum of 5 weeks, and there was no clinical evidence of scarring in 26 out of 28 cases. In this study we achieved a cure rate of 92.86% in a 6-month period. Further follow-up after 3 years yielded almost the same result, except that one patient was not available for follow-up. We concluded that Nd:YAG laser is an effective device in the management of oral leukoplakia, which is one of the major pre-cancerous lesions in our country.

Acetaldehyde inhibits the formation of retinoic acid from retinal in the rat esophagus

OBJECTIVE

It has already been demonstrated that the rat esophagus produces retinoic acid from retinol. In this study, this process is further characterized and the effect of acetaldehyde examined to elucidate the possible mechanisms behind the epidemiological evidence that the incidence of esophageal cancer is higher in alcoholics.

MATERIAL AND METHODS

Rat esophageal samples were incubated with all-trans retinal and newly formed all-trans retinoic acid (ATRA) was quantified using high-performance liquid chromatography (HPLC). Furthermore, beta-nicotinamide adenine dinucleotide (NAD)-dependent acetaldehyde oxidation by the rat esophagus was examined by tracing NAD reduction using a spectrophotometer.

RESULTS

Rat esophageal samples produced ATRA from all-trans retinal in a NAD-dependent manner and the potential was significantly attenuated by phenetyl isothiocynate, an ALDH inhibitor, or acetaldehyde depending on the concentration used. Rat esophageal samples also oxidized acetaldehyde of various concentrations NAD dependently. The ATRA formation potential that was temporarily inhibited by acetaldehyde was recovered to the control level by dialysis when the specimen was incubated with up to 50 microM of acetaldehyde.

CONCLUSIONS

The rat esophagus produces retinoic acid from retinal. An ALDH isoform(s) is responsible for this process and physiological concentration of acetaldehyde hampers the process, probably in a competitive manner. Since the disturbance of retinoic acid supply has been implicated in carcinogenicity, this finding may, at least in part, explain the high incidence of esophageal cancer in alcoholics, especially in those with inactive ALDH 2 whose blood acetaldehyde levels become higher than those with active ALDH 2.

Chemoprevention of squamous cell carcinoma in recessive dystrophic epidermolysis bullosa: results of a phase 1 trial of systemic isotretinoin

BACKGROUND

Patients with recessive dystrophic epidermolysis bullosa (RDEB) are at high risk of developing squamous cell carcinoma on or after midadolescence, and most patients die of metastatic squamous cell carcinoma within 5 years of diagnosis of their first squamous cell carcinoma.

OBJECTIVE

We sought to determine whether isotretinoin can be safely administered to patients with RDEB as a possible chemopreventive agent.

METHODS

A total of 20 patients with RDEB aged 15 years or older were treated daily for 8 months with isotretinoin (with a targeted dosage of 0.5 mg/kg/d).

RESULTS

No unusual adverse reactions were noted in this patient population. Several patients experienced reduced blistering at lower doses and increased mechanical fragility at maintenance dosage.

CONCLUSIONS

Isotretinoin, at least up to a dosage of 0.5 mg/kg/d, may be safely used in patients with RDEB. Although increased fragility may occur, patients tolerated this drug well and were receptive to its long-term use for possible chemoprevention of cancer. Whether such an effect will occur is yet to be proven.

Prophylaxis of oral mucositis in irradiated head-and-neck cancer patients: a proposed classification scheme of interventions and meta-analysis of randomized controlled trials

PURPOSE

To identify, classify, and evaluate agents used in the prophylaxis of oral mucositis in irradiated head and neck cancer patients.

METHODS

Data sources included multiple databases and manual citation review of relevant literature. Based on the eligibility criteria, 59 studies were independently reviewed by two reviewers. Forty-two studies were included in the classification scheme, of which 15 met the criteria for inclusion in the meta-analysis. Data were extracted by duplicate independent review, with disagreement resolved by consensus.

RESULTS

Overall, the interventions reduced the odds of developing severe oral mucositis, when assessed by clinicians, by 36% (OR: 0.64; 95% CI: 0.46, 0.88). Subgroup analysis suggested that only the narrow-spectrum antibacterial lozenges were effective (OR: 0.45; 95% CI: 0.23, 0.86); however, the power of the aggregated data in the other classes may have been insufficient to detect differences. When the outcome was assessed by patients, no significant difference was seen in the outcome between the treatment and the control groups (OR: 0.79; 95% CI: 0.56-1.12).

CONCLUSIONS

Overall, interventions chosen on a sound biologic basis to prevent severe oral mucositis are effective. In particular, when oral mucositis is assessed by clinicians, narrow-spectrum antibiotic lozenges appear to be beneficial. Methodologic limitations were evident in many of the studies. Further research using validated measurement tools in larger, methodologically sound trials is warranted.

Epithelial structural proteins of the skin and oral cavity: function in health and disease

Epithelial tissues function to protect the organism from physical, chemical, and microbial damage and are essential for survival. To perform this role, epithelial keratinocytes undergo a well-defined differentiation program that results in the expression of structural proteins which maintain the integrity of epithelial tissues and function as a protective barrier. This review focuses on structural proteins of the epidermis and oral mucosa. Keratin proteins comprise the predominant cytoskeletal component of these epithelia. Keratin filaments are attached to the plasma membrane via desmosomes, and together these structural components form a three-dimensional array within the cytoplasm of epithelial cells and tissues. Desmosomes contain two types of transmembrane proteins, the desmogleins and desmocollins, that are members of the cadherin family. The desmosomal cadherins are linked to the keratin cytoskeleton via several cytoplasmic plaque proteins, including desmoplakin and plakoglobin (gamma-catenin). Epidermal and oral keratinocytes express additional differentiation markers, including filaggrin and trichohyalin, that associate with the keratin cytoskeleton during terminal differentiation, and proteins such as loricrin, small proline-rich proteins, and involucrin, that are cross-linked into the cornified envelope by transglutaminase enzymes. The importance of these cellular structures is highlighted by the large numbers of genetic and acquired (autoimmune) human disorders that involve mutations in, or autoantibodies to, keratins and desmosomal and cornified envelope proteins. While much progress has been made in the identification of the structural proteins and enzymes involved in epithelial differentiation, regulation of this process is less clear. Both calcium and retinoids influence epithelial differentiation by altering the transcription of target genes and by regulating activity of enzymes critical in epithelial differentiation, such as transglutaminases, proteinases, and protein kinases. These studies have furthered our understanding of how epithelial tissue and cell integrity is maintained and provide a basis for the future treatment of skin and oral disorders by gene therapy and other novel therapeutics.

bcl-2 expression and apoptotic bodies in 13-cis-retinoic acid (isotretinoin)-topically treated oral leukoplakia: a pilot study

In a double-blind study 10 patients with oral leukoplakia were treated daily (three topical applications) with 0.1% isotretinoin gel or a placebo for 4 months. Nine patients completed the treatment, while one patient was lost to follow-up. Subsequently, the patients who had received the placebo used the active medication for an additional 4 months. All patients treated with the active medication showed a significant improvement of the oral lesions while, in the patients receiving only the placebo, the size of the lesions remained the same. Also the group of patients who received the active medication after the placebo showed an improvement in the size and clinical appearance of the lesions. A complete response was defined as the complete disappearance of the lesion as assessed by visual inspection, while a partial response was defined as a 50% or more reduction in the size of the lesions. In total we had a complete response and eight partial responses. No side-effects from the use of the gel were ever observed. The percentage of bcl-2-positive cells was evaluated in the basal layer from a minimum of 1000 cells in each case and the bcl-2 immunostaining was scored using three groups: - (< or = 10% cells); + (< or = 50% cells); +2 (> or = 50% cells). The presence of apoptotic bodies was evaluated in a random fashion in the parabasal layer in 20 HPF. Immunohistochemical analysis for bcl-2 protein showed that before treatment a weak positivity of the basal layers, with a focal positivity of some parabasal cells, was present: five out of nine specimens were positive. Only a few apoptotic bodies were observed. After treatment in almost all specimens it was possible to observe a complete bcl-2 negativity with a positivity in only one specimen out of nine. An increase in apoptotic bodies was observed. Statistical analysis showed that the difference between the bcl-2 positivity in the two groups was not statistically significant (P = 0.134) while, on the contrary, the difference in the count of the apoptotic bodies between the same two groups was statistically significant (P = 0.0193). In conclusion, the data obtained from this pilot study show that good results can be obtained with the topical use of 13-cis-retinoic acid.

Oral leukoplakia: a clinicopathological review

Leukoplakia is the most common premalignant or potentially malignant lesion of the oral mucosa. It seems preferable to use the term leukoplakia as a clinical term only. When a biopsy is taken, the term leukoplakia should be replaced by the diagnosis obtained histologically. The annual percentage of malignant transformation varies in different parts of the world, probably as a result of differences in tobacco and dietary habits. Although epithelial dysplasia is an important predictive factor of malignant transformation, it should be realized that not all dysplastic lesions will become malignant. On the other hand non-dysplastic lesions may become malignant as well. In some parts of the world the tongue and the floor of the mouth can be considered to be high-risk sites with regard to malignant transformation of leukoplakia, while this does not have to be the case in other parts of the world. The cessation of tobacco habits, being the most common known aetiological factor of oral leukoplakia, has been shown to be an effective measure with regard to the incidence of leukoplakia and, thereby, the incidence of oral cancer as well. Screening for oral precancer may be indicated in individuals at risk.