Oral premalignant lesions: any progress with systemic therapies?

Cancer Precursor Syndromes and Their Detection in the Head and Neck

This article explores the multifaceted landscape of oral cancer precursor syndromes. Hereditary disorders like dyskeratosis congenita and Fanconi anemia increase the risk of malignancy. Oral potentially malignant disorders, notably leukoplakia, are discussed as precursors influenced by genetic and immunologic facets. Molecular insights delve into genetic mutations, allelic imbalances, and immune modulation as key players in precancerous progression, suggesting potential therapeutic targets. The article navigates the controversial terrain of management strategies of leukoplakia, encompassing surgical resection, chemoprevention, and immune modulation, while emphasizing the ongoing challenges in developing effective, evidence-based preventive approaches.

Management of oral leukoplakia: a position paper of the Society of Oral Medicine, Chinese Stomatological Association

OBJECTIVE

The objective of this study was to develop the first edition of a Chinese evidence-based position paper on the management of oral leukoplakia (OLK).

STUDY DESIGN

The consultant group for drafting the position paper consisted of 31 oral medicine specialists and 2 evidence-based medicine specialists. English studies (searched in PubMed, EMBASE, and the Cochrane Library) and Chinese studies (searched in China National Knowledge Infrastructure and WanFang) published before January 2018 were used. The quality of the study was assessed using the Grading of Recommendations Assessment, Development, and Evaluation grid, and the strength of the recommendations was determined based on the results of 3 rounds of voting among the consultant group members using the Delphi method.

RESULTS

Twenty-two evidence-based guidelines for clinical management and monitoring of OLK were established in this position paper. A clinical path diagram for oral health practitioners was constructed based on the recommendations.

CONCLUSION

Current evidence suggests that management and monitoring of patients with OLK should be performed by experienced clinicians to control the lesion and for early detection of malignant transformation. However, all recommendations are based on evidence of low or extremely low quality and may require further modification as new evidence is produced.

Potential of Melatonin as Adjuvant Therapy of Oral Cancer in the Era of Epigenomics

The wide variety of epigenetic controls available is rapidly expanding the knowledge of molecular biology even overflowing it. At the same time, it can illuminate unsuspected ways of understanding the etiology of cancer. New emerging therapeutic horizons, then, promise to overcome the current antitumor strategies need. The translational utility of this complexity is particularly welcome in oral cancer (OC), in which natural history is alarmingly disappointing due to the invasive and mutilating surgery, the high relapsing rate, the poor quality of life and the reduced survival after diagnosis. Melatonin activates protective receptor-dependent and receptor-independent processes that prevent tissue cancerisation and inhibit progressive tumor malignancy and metastasis. Related evidence has shown that melatonin pleiotropy encompasses gene expression regulation through all the three best-characterized epigenetic mechanisms: DNA methylation, chromatin modification, and non-coding RNA. OC has received less attention than other cancers despite prognosis is usually negative and there are no significant therapy improvements recorded in the past decade. However, a large research effort is being carried out to elucidate how melatonin´s machinery can prevent epigenetic insults that lead to cancer. In the light of recent findings, a comprehensive examination of biochemistry through which melatonin may reverse epigenetic aberrations in OC is an extraordinary opportunity to take a step forward in the clinical management of patients.

Chemoprevention of Head and Neck Cancers: Does It Have Only One Face?

Head and neck squamous cell cancer (HNSCC) represents a significant burden worldwide. Chemoprevention of HNSCC is a means of cancer control with a use of drugs or natural agents in order to hinder or delay the cancer development. The purpose of this article is to review mechanism of action of different chemopreventive agents' groups and results of most important researches concerning them. The safety issues of HNSCC chemoprevention are also discussed. In case of HNSCC there is currently no agent, which would give positive result in the third phase of clinical trials. Promising results of preclinical trials are not always confirmed by further tests. Main problems are low effectiveness, high toxicity, and lack of highly specificity biomarkers for monitoring the research. New trials concerning many agents, as well as novel technologies for provision of pharmaceutical forms of them, including drug nanocarriers, are currently underway, which gives hope for finding the perfect chemopreventive agent formula.

Reduced CD8+ T cells infiltration can be associated to a malignant transformation in potentially malignant oral epithelial lesions

OBJECTIVE

The aim of this study was to evaluate the immunohistochemical expressions of PD1, CD4⁺, and CD8⁺ in premalignant lesions (OPML) that were transformed into oral squamous cell carcinoma OSCC (OPML-OSCC), in OSCC and also in premalignant lesions that were not transformed into OSCC (OPML-NOSSC).

MATERIALS AND METHODS

Retrospective analyses were performed in order to verify the demographic characteristics of the patients. CD4, CD8, and PD1 IMH studies were carried out on OPML and OSCC samples from 11 patients with OPML-OSCC and OPML, together with samples from 14 patients with OPML-NOSCC. The differences between OPML-OSCC and OPML-NOSCC were analyzed.

RESULTS

Non-homogenous leukoplakia, together with the related oral subsite, and the lack of an exposure to tobacco, were all associated with malignant transformations. There were no statistical differences in the PD1 expression and the CD4⁺ cells in OPML-OSCC and OPML-NOSCC. A significant increment in the CD8⁺ cells was noted in the OPML that evolved into carcinomas when compared with OPML-NOSCC (p = 0.05), whereas there were higher CD8⁺ cells levels in the carcinomas when compared with the OPML that evolved into carcinomas (p = 0.027).

CONCLUSIONS

CD8⁺ cells infiltrate more in OPML-NOSCC than in OPML-OSCC. Carcinoma is more infiltrated by CD8⁺ cells than its associated OPML.

CLINICAL RELEVANCE

Understanding immunological factors associated with malignant transformation of oral premalignant lesions can open a new way to treat this disease.

Oral leukoplakia and proliferative verrucous leukoplakia: a review for dental practitioners

Objectives To provide an overview of the current thinking in terms of the diagnosis and management of oral leukoplakia and proliferative verrucous leukoplakia as relevant to general dental practitioners.Data sources, data selection, data extraction, data synthesis We searched the MEDLINE Ovid, EMBASE databases and the Cochrane Library, (1990 to 16 April 2017), restricting our search to English language with the following key words: leukoplakia, white patch, proliferative verrucous leukoplakia, precancerous lesion, premalignant lesions, potentially malignant oral conditions and potentially malignant oral disorders. The two authors selected key papers and engaged in collaborative data extraction and synthesis of the selected reference material.Conclusions General dental practitioners (GDPs) are likely to encounter patients with a known or yet undiagnosed oral leukoplakia in their clinical practice. The diagnosis is clinically based as there are no pathognomonic histopathological features. The definition of leukoplakia has evolved over the years. The importance of recognition and appropriate management relating to this condition is described particularly as it is one of the oral potentially malignant lesions. The inferred increased risk of malignant transformation is well documented however controversy still persists in terms of the appropriate management for these lesions. Proliferative verrucous leukoplakia is a recalcitrant, often widespread and multifocal distinct type of leukoplakia. It is considered to have a high rate of malignant transformation with implications in terms of lifelong monitoring both clinically and histopathologically. A high index of suspicion is important for general dental practitioners in order to identify such lesions that would require onward referral for further investigation and management.

Genomic profile of oral squamous cell carcinomas with an adjacent leukoplakia or with an erythroleukoplakia that evolved after the treatment of primary tumor: A report of two cases

Oral leukoplakia and erythroleukoplakia are common oral potentially malignant disorders diagnosed in the oral cavity. The specific outcome of these lesions remains to be elucidated, as their malignant transformation rate exhibits great variation. The ability to predict which of those potentially malignant lesions are likely to progress to cancer would be vital to guide their future clinical management. The present study reported two patients with tongue squamous cell carcinoma: Case study 1 was diagnosed with a simultaneous leukoplakia and case study 2 developed an erythroleukoplakia following the primary tumor treatment. Whole genome copy number alterations were analyzed using array comparative genomic hybridization. The present study determined more genomic imbalances in the tissues from leukoplakia and erythroleukoplakia compared with their respective tumors. The present study also identified in tumor and potentially malignant lesions common alterations of chromosomal regions and genes, including FBXL5, UGT2B15, UGT2B28, KANSL1, GSTT1 and DUSP22, being some of these typical aberrations described in oral cancer and others are linked to chemoradioresistance. Several putative genes associated with hallmarks of malignancy that may have an important role in predicting the progression of leukoplakia and erythroleukoplakia to squamous cell carcinoma, namely gains in BNIPL, MCL1, STAG2, CSPP1 and ZNRF3 genes were also identified.

Prognostic factors, predictive markers and cancer biology: the triad for successful oral cancer chemoprevention

Oral squamous cell carcinomas represent a significant cancer burden worldwide. Unfortunately, chemoprevention strategies investigated to date have failed to produce an agent considered standard of care to prevent oral cancers. Nonetheless, recent advances in clinical trial design may streamline drug development in this setting. In this manuscript, we review some of these improvements, including risk prediction tools based on molecular markers that help select patients most suitable for chemoprevention. We also discuss the opportunities that novel preclinical models and modern molecular profiling techniques will bring to the prevention field in the near future, and propose a clinical trials framework that incorporates molecular prognostic factors, predictive markers and cancer biology as a roadmap to improve chemoprevention strategies for oral cancers.

Mouth Cancer for Clinicians Part 6: Potentially Malignant Disorders

A MEDLINE search early in 2015 revealed more than 250,000 papers on head and neck cancer; over 100,000 on oral cancer; and over 60,000 on mouth cancer. Not all publications contain robust evidence. We endeavour to encapsulate the most important of the latest information and advances now employed in practice, in a form comprehensible to healthcare workers, patients and their carers. This series offers the primary care dental team, in particular, an overview of the aetiopathogenesis, prevention, diagnosis and multidisciplinary care of mouth cancer, the functional and psychosocial implications, and minimization of the impact on the quality of life of patient and family.

CLINICAL RELEVANCE

This article offers the dental team an overview of oral potentially malignant disorders.

Fenretinide Perturbs Focal Adhesion Kinase in Premalignant and Malignant Human Oral Keratinocytes. Fenretinide's Chemopreventive Mechanisms Include ECM Interactions

The membrane-associated protein, focal adhesion kinase (FAK), modulates cell-extracellular matrix interactions and also conveys prosurvival and proliferative signals. Notably, increased intraepithelial FAK levels accompany transformation of premalignant oral intraepithelial neoplasia (OIN) to oral squamous cell carcinoma (OSCC). OIN chemoprevention is a patient-centric, optimal strategy to prevent OSCC's comorbidities and mortality. The cancer chemopreventive and synthetic vitamin A derivative, fenretinide, has demonstrated protein-binding capacities, for example, mTOR- and retinol-binding protein interactions. These studies used a continuum of human oral keratinocytes (normal-HPV E6/E7-transduced-OSCC) to assess potential fenretinide-FAK drug protein interactions and functional consequences on cellular growth regulation and motility. Molecular modeling studies demonstrated that fenretinide has approximately 200-fold greater binding affinity relative to the natural ligand (ATP) at FAK's kinase domain. Fenretinide also shows intermediate binding at FAK's FERM domain and interacts at the ATP-binding site of the closest FAK analogue, PYK2. Fenretinide significantly suppressed proliferation via induction of apoptosis and G2-M cell-cycle blockade. Fenretinide-treated cells also demonstrated F-actin disruption, significant inhibition of both directed migration and invasion of a synthetic basement membrane, and decreased phosphorylation of growth-promoting kinases. A commercially available FAK inhibitor did not suppress cell invasion. Notably, although FAK's FERM domain directs cell invasion, FAK inhibitors target the kinase domain. In addition, FAK-specific siRNA-treated cells showed an intermediate cell migration capacity; data which suggest cocontribution of the established migrating-enhancing PYK2. Our data imply that fenretinide is uniquely capable of disrupting FAK's and PYK2's prosurvival and mobility-enhancing effects and further extend fenretinide's chemopreventive contributions beyond induction of apoptosis and differentiation.

A novel target for oral cancer chemoprevention? Notch quite, yet…

The two major goals of oral cancer chemoprevention efforts are the ability to segregate the high-risk patients and the identification of an effective pharmacologic agent that halts progression to invasive cancer. Considerable progress has recently been achieved in profiling invasive head and neck squamous cell carcinomas, particularly with the use of high-throughput technologies. A similar molecular characterization of potentially malignant oral epithelial lesions (OPML; leukoplakia and erythroplakia) is yet to be accomplished. It is postulated, though, that molecular profiling could lead to the discovery of novel markers of cancer risk that could also serve as potential targets for chemoprevention. In this perspective, we comment on the work by Izumchenko and colleagues that reports a high prevalence of NOTCH1 gain-of-function mutations in Chinese patients with OPMLs. Although additional studies are needed to validate the findings, the study is the first to link alterations in this gene in oral premalignancy. These findings could serve as a first prototype of a single gene mutation as a potential target in clinical chemoprevention setting.

Retinoic acid receptors: from molecular mechanisms to cancer therapy

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

Oral and oropharyngeal cancer

Oral and oropharyngeal cancer (OPC) is a complex and often relentless malignancy prone to local invasion and dissemination. Despite advances in understanding of the disease and improved therapeutic interventions, it continues to be diagnosed at an advanced stage and the survival rate remains poor. The financial cost of treating OPC may be the highest of all cancers in the United States and survivors often experience major detriments to quality of life. Major risk factors for OPC are tobacco, alcohol, areca nut, and human papillomavirus infection. This article updates medical practitioners on the causes, presentation, diagnosis, and management of OPC.

Treatment of oral leukoplakia with a low-dose of beta-carotene and vitamin C supplements: a randomized controlled trial

Management of oral leukoplakia-a potentially malignant disorder-is currently not evidence-based. Of the few randomized trials that have been reported, most have negative data. Therefore, a multi-centre, randomized, double-blind controlled trial (RCT) was undertaken to evaluate the use of low-dose beta-carotene combined with vitamin C supplements for the treatment and to prevent malignant transformation of oral leukoplakia. 46 Japanese participants with oral leukoplakia were allocated randomly either to an experimental arm (10 mg day(-1) of beta-carotene and 500 mg day(-1) of vitamin C) or placebo arm (50 mg day(-1) of vitamin C). Current or ex-smokers within 3 months of cessation were excluded. The supplements were continued over a period of 1 year. The primary endpoint was clinical remission at 1-year and the likelihood of malignant transformation during a 5-year follow-up period as a secondary endpoint. The overall clinical response rate in the experimental arm was 17.4% (4/23) and 4.3% (1/23) in the placebo arm (p = 0.346). During the median 60-month follow-up period, two subjects in the experimental arm and three in the control arm developed oral cancer. Under the intention-to-treat principle, relative risk by supplementing with beta-carotene and vitamin C was 0.77 (95%CI: 0.28-1.89) (p = 0.580) by the Cox proportional hazards model. No unfavorable side-effects were noted. Beta-carotene (10 mg day(-1) ) and vitamin C were neither effective for clinical remission, nor for protection against the development of cancer. Data from this RCT does not support the hypothesis that chemoprevention with this treatment is effective for oral leukoplakia.

Melatonin in the oral cavity: physiological and pathological implications

BACKGROUND AND OBJECTIVES

The purpose of this article was to summarize what is known about the function of melatonin in the oral cavity.

MATERIAL AND METHODS

Databases were searched for the relevant published literature to 30 November, 2013. The following search items were used in various combinations: melatonin, gingiva, periodontium, inflammation, herpes, alveolar bone, periodontal ligament, dental implants, xerostomia, methacrylate, chlorhexidine, cancer. The literature uncovered is summarized herein.

RESULTS

Salivary melatonin levels exhibit a circadian rhythm with highest values at night. Melatonin has both receptor-mediated and receptor-independent actions in cells of the oral cavity. Melatonin is released into the saliva by the acinar cells of the major salivary glands and via the gingival fluid. Functions of melatonin in the oral cavity are likely to relate primarily to its anti-inflammatory and antioxidant activities. These actions may suppress inflammation of the gingiva and periodontium, reduce alveolar bone loss, abrogate herpes lesions, enhance osteointegration of dental implants, limit oral cancer, and suppress disorders that have a free radical component. Sublingual melatonin tablets or oral melatonin sprays and topical melatonin-containing gel, if used on a regular basis, may improve overall oral health and reduce mucosal lesions.

CONCLUSION

Collectively, the results indicate that endogenously-produced and exogenously-applied melatonin are beneficial to the oral cavity.

Topical application of a mucoadhesive freeze-dried black raspberry gel induces clinical and histologic regression and reduces loss of heterozygosity events in premalignant oral intraepithelial lesions: results from a multicentered, placebo-controlled clinical trial

PURPOSE

Approximately 30% higher grade premalignant oral intraepithelial neoplasia (OIN) lesions will progress to oral cancer. Although surgery is the OIN treatment mainstay, many OIN lesions recur, which is highly problematic for both surgeons and patients. This clinical trial assessed the chemopreventive efficacy of a natural product-based bioadhesive gel on OIN lesions.

EXPERIMENTAL DESIGN

This placebo-controlled multicenter study investigated the effects of topical application of bioadhesive gels that contained either 10% w/w freeze-dried black raspberries (BRB) or an identical formulation devoid of BRB placebo to biopsy-confirmed OIN lesions (0.5 g × q.i.d., 12 weeks). Baseline evaluative parameters (size, histologic grade, LOH events) were comparable in the randomly assigned BRB (n = 22) and placebo (n = 18) gel cohorts. Evaluative parameters were: histologic grade, clinical size, and LOH.

RESULTS

Topical application of the BRB gel to OIN lesions resulted in statistically significant reductions in lesional sizes, histologic grades, and LOH events. In contrast, placebo gel lesions demonstrated a significant increase in lesional size and no significant effects on histologic grade or LOH events. Collectively, these data strongly support BRB's chemopreventive impact. A cohort of very BRB-responsive patients, as demonstrated by high therapeutic efficacy, was identified. Corresponding protein profiling studies, which demonstrated higher pretreatment levels of BRB metabolic and keratinocyte differentiation enzymes in BRB-responsive lesions, reinforce the importance of local metabolism and differentiation competency.

CONCLUSIONS

Results from this trial substantiate the LOH reductions identified in the pilot BRB gel study and extend therapeutic effects to significant improvements in histologic grade and lesional size.

Management for premalignant lesions of the oral cavity

Premalignant lesions of the oral cavity present as visibly abnormal areas of mucosa and may be a source of significant anxiety for the patient and the clinician. Suspicious lesions should be biopsied to evaluate for dysplasia. The risk of malignant transformation may relate to patient characteristics, environmental risk factors and genetic alterations. Management of such lesions hinges on risk modification, surveillance, symptom management and directed biopsies. Excision or ablation of dysplastic lesions is indicated. We review the current evidence relating to management of premalignant lesions of the oral mucosa and make recommendations for practice patterns.

Optimizing biomarkers and endpoints in oral cancer chemoprevention trials

Chemoprevention, defined as the use of natural, synthetic, or biologic compounds to halt, reverse, or prevent the initial phases of carcinogenesis or the progression of neoplastic cells to cancer, has produced successes, but progress has been slow. Notably, in the field of oral cancer prevention and despite extensive clinical investigations, a standard systemic therapy for patients with oral premalignant lesions is yet to be developed. In view of safety concerns surrounding the use of pharmaceuticals, the use of phytochemicals derived from the diet has been considered but has not yet translated into clinical success. The Bowman Birk Inhibitor (BBI) is a serine protease inhibitor isolated from soybeans possessing domains with trypsin and chymotrypsin inhibitory activity. Encouraging results were previously reported in a phase IIa trial of BBI complex in patients with oral leukoplakia with measurable clinical responses and favorable biomarker changes. In this issue of the journal, the less promising results of the randomized, placebo-controlled phase IIb trial are presented. In this commentary, the complexities involved in defining optimal biomarkers and endpoints for oral cancer prevention trials and the development of dietary chemoprevention agents are discussed.

Oral premalignancy: the roles of early detection and chemoprevention

Premalignancy and chemoprevention studies in head and neck cancer typically focus on the oral cavity. Avoiding or cessation of alcohol and smoking, early detection of potentially malignant disorders or cancer, and early detection of recurrent and/or second primary tumor form the basis of prevention of oral cancer. Analysis of tissue prospectively collected in evaluation of retinoids for chemoprevention trials allowed identification of molecular biomarkers of risk to develop oral cancer, loss of heterozygosity being the most validated one. Improving risk assessment and identification of new targets for chemoprevention represent the main challenges in this field.