Perineural invasion is associated with function-evoked pain and altered extracellular matrix in patients with head and neck squamous cell carcinoma.

Head and neck squamous cell carcinoma (HNSCC) is painful, and perineural invasion (PNI) has been associated with worst pain. Pain due to HNSCC is diverse and may vary based on clinicopathological factors. This study aims to characterize different pain patterns linked with PNI, its influence on daily functioning, and gain insights into molecular changes and pathways associated with PNI-related pain in HNSCC patients. We conducted a cross-sectional study across three medical centers (n=114), assessing pain phenotypes and their impact on daily functioning using two self-reported pain questionnaires, given to patients prior to their cancer surgery. Furthermore, we conducted RNA-seq analysis utilizing the TCGA dataset of HNSCC tumor from patients (n=192) to identify genes relevant to both PNI and pain. Upon adjusting for demographic and clinicopathological variables using linear regression models, we found that PNI independently predicted function-evoked pain according to the UCSF Oral Cancer Pain Questionnaire, as well as the worst pain intensity reported in the Brief Pain Inventory. Distinct pain patterns were observed to be associated with daily activities in varying manners. Our molecular analyses revealed significant disruptions in pathways associated with extracellular matrix (ECM) structure and organization. The top differentially expressed genes linked to the ECM are implicated in cancer development, pain, and neurodegenerative diseases. Our data underscore the importance of properly categorizing pain phenotypes in future studies aiming to uncover mechanistic underpinnings of pain. Additionally, we have compiled a list of genes of interest that could serve as targets for both cancer and cancer pain management. PERSPECTIVE: PNI independently predicts function-evoked pain. Different pain phenotypes affect daily activities differently. We identified a list of candidate genes involved in extracellular matrix structure and function that can be targeted for both cancer and cancer pain control.

Artificial intelligence-based epigenomic, transcriptomic and histologic signatures of tobacco use in oral squamous cell carcinoma.

Oral squamous cell carcinoma (OSCC) biomarker studies rarely employ multi-omic biomarker strategies and pertinent clinicopathologic characteristics to predict mortality. In this study we determine for the first time a combined epigenetic, gene expression, and histology signature that differentiates between patients with different tobacco use history (heavy tobacco use with ≥10 pack years vs. no tobacco use). Using The Cancer Genome Atlas (TCGA) cohort (n = 257) and an internal cohort (n = 40), we identify 3 epigenetic markers (GPR15, GNG12, GDNF) and 13 expression markers (IGHA2, SCG5, RPL3L, NTRK1, CD96, BMP6, TFPI2, EFEMP2, RYR3, DMTN, GPD2, BAALC, and FMO3), which are dysregulated in OSCC patients who were never smokers vs. those who have a ≥ 10 pack year history. While mortality risk prediction based on smoking status and clinicopathologic covariates alone is inaccurate (c-statistic = 0.57), the combined epigenetic/expression and histologic signature has a c-statistic = 0.9409 in predicting 5-year mortality in OSCC patients.

Single-Cell Molecular Profiling of Head and Neck Squamous Cell Carcinoma Reveals Five Dysregulated Signaling Pathways Associated With Circulating Tumor Cells.

OBJECTIVES: To determine the dysregulated signaling pathways of head and neck squamous cell carcinoma associated with circulating tumor cells (CTCs) via single-cell molecular characterization. INTRODUCTION: Head and neck squamous cell carcinoma (HNSCC) has a significant global burden and is a disease with poor survival. Despite trials exploring new treatment modalities to improve disease control rates, the 5 year survival rate remains low at only 60%. Most cancer malignancies are reported to progress to a fatal phase due to the metastatic activity derived from treatment-resistant cancer cells, regarded as one of the most significant obstacles to develope effective cancer treatment options. However, the molecular profiles of cancer cells have not been thoroughly studied. METHODS: Here, we examined in-situ HNSCC tumors and pairwisely followed up with the downstream circulating tumor cells (CTCs)-based on the surrogate biomarkers to detect metastasis that is established in other cancers - not yet being fully adopted in HNSCC treatment algorithms. RESULTS: Specifically, we revealed metastatic HNSCC patients have complex CTCs that could be defined through gene expression and mutational gene profiling derived from completed single-cell RNASeq (scRNASeq) that served to confirm molecular pathways inherent in these CTCs. To enhance the reliability of our findings, we cross-validated those molecular profiles with results from previously published studies. CONCLUSION: Thus, we identified 5 dysregulated signaling pathways in CTCs to derive HNSCC biomarker panels for screening HNSCC in situ tumors.

ObjectivesInvestigating the dysregulated signaling pathways of head and neck squamous cell carcinoma (HNSCC) linked with circulating tumor cells (CTCs) using single-cell molecular characterization.IntroductionHNSCC poses a significant global health burden with poor survival rates despite advancements in treatment. Metastatic activity from treatment-resistant cancer cells remains a major challenge in developing effective treatments. However, the molecular profiles of cancer cells, particularly CTCs, are not well-understood.MethodsWe analyzed in-situ HNSCC tumors and corresponding CTCs using surrogate biomarkers to detect metastasis, a technique not widely used in HNSCC treatment protocols.ResultsOur study revealed complex CTCs in metastatic HNSCC patients characterized by gene expression and mutational gene profiling via single-cell RNASeq (scRNASeq). These profiles confirmed molecular pathways inherent in CTCs, further validated by previous research.ConclusionThrough our research, we identified five dysregulated signaling pathways in CTCs, suggesting potential biomarker panels for HNSCC screening in situ tumors.

Stimulator of Interferon Genes Pathway Activation through the Controlled Release of STINGel Mediates Analgesia and Anti-Cancer Effects in Oral Squamous Cell Carcinoma.

Oral squamous cell carcinoma (OSCC) presents significant treatment challenges due to its poor survival and intense pain at the primary cancer site. Cancer pain is debilitating, contributes to diminished quality of life, and causes opioid tolerance. The stimulator of interferon genes (STING) agonism has been investigated as an anti-cancer strategy. We have developed STINGel, an extended-release formulation that prolongs the availability of STING agonists, which has demonstrated an enhanced anti-tumor effect in OSCC compared to STING agonist injection. This study investigates the impact of intra-tumoral STINGel on OSCC-induced pain using two separate OSCC models and nociceptive behavioral assays. Intra-tumoral STINGel significantly reduced mechanical allodynia in the orofacial cancer model and alleviated thermal and mechanical hyperalgesia in the hind paw model. To determine the cellular signaling cascade contributing to the antinociceptive effect, we performed an in-depth analysis of immune cell populations via single-cell RNA-seq. We demonstrated an increase in M1-like macrophages and N1-like neutrophils after STINGel treatment. The identified regulatory pathways controlled immune response activation, myeloid cell differentiation, and cytoplasmic translation. Functional pathway analysis demonstrated the suppression of translation at neuron synapses and the negative regulation of neuron projection development in M2-like macrophages after STINGel treatment. Importantly, STINGel treatment upregulated TGF-ß pathway signaling between various cell populations and peripheral nervous system (PNS) macrophages and enhanced TGF-ß signaling within the PNS itself. Overall, this study sheds light on the mechanisms underlying STINGel-mediated antinociception and anti-tumorigenic impact.

Innovations in Molecular Biomarkers and Biomaterial-Based Immunotherapies for Head & Neck Cancer.

Purpose of Review: Oral squamous cell carcinoma (OSCC) survival rates have remained stagnant due to a lack of targeted therapies and diagnostic tools. Patient risk is currently determined solely through clinicopathologic features, primarily tumor staging, which lacks the necessary precision to stratify patients by risk and accurately dictate adjuvant treatment. Similarly, conventional OSCC therapies have well-established toxicities and limited efficacy. Recent Findings: Recent studies show that patient risk can now be assessed using non-invasive techniques, at earlier time points, and with greater accuracy using molecular biomarker panels. Additionally, novel immunotherapies not only utilize the host's immune response to combat disease but also have the potential to form immunological memory to prevent future recurrence. Localized controlled-release formulas have further served to reduce toxicity and allow the de-escalation of other treatment modalities. Summary: We review the latest advances in head and neck cancer diagnosis and treatment, including novel molecular biomarkers and immunotherapies.

Repurposing EGFR Inhibitors for Oral Cancer Pain and Opioid Tolerance.

Oral cancer pain remains a significant public health concern. Despite the development of improved treatments, pain continues to be a debilitating clinical feature of the disease, leading to reduced oral mobility and diminished quality of life. Opioids are the gold standard treatment for moderate-to-severe oral cancer pain; however, chronic opioid administration leads to hyperalgesia, tolerance, and dependence. The aim of this review is to present accumulating evidence that epidermal growth factor receptor (EGFR) signaling, often dysregulated in cancer, is also an emerging signaling pathway critically involved in pain and opioid tolerance. We presented preclinical and clinical data to demonstrate how repurposing EGFR inhibitors typically used for cancer treatment could be an effective pharmacological strategy to treat oral cancer pain and to prevent or delay the development of opioid tolerance. We also propose that EGFR interaction with the µ-opioid receptor and glutamate N-methyl-D-aspartate receptor could be two novel downstream mechanisms contributing to pain and morphine tolerance. Most data presented here support that repurposing EGFR inhibitors as non-opioid analgesics in oral cancer pain is promising and warrants further research.

Neurotrophin Pathway Receptors NGFR and TrkA Control Perineural Invasion, Metastasis, and Pain in Oral Cancer.

Oral squamous cell carcinoma (OSCC) patients suffer from poor survival due to metastasis or locoregional recurrence, processes that are both facilitated by perineural invasion (PNI). OSCC has higher rates of PNI than other cancer subtypes, with PNI present in 80% of tumors. Despite the impact of PNI on oral cancer prognosis and pain, little is known about the genes that drive PNI, which in turn drive pain, invasion, and metastasis. In this study, clinical data, preclinical, and in vitro models are leveraged to elucidate the role of neurotrophins in OSCC metastasis, PNI, and pain. The expression data in OSCC patients with metastasis, PNI, or pain demonstrate dysregulation of neurotrophin genes. TrkA and nerve growth factor receptor (NGFR) are focused, two receptors that are activated by NGF, a neurotrophin expressed at high levels in OSCC. It is demonstrated that targeted knockdown of these two receptors inhibits proliferation and invasion in an in vitro and preclinical model of OSCC, and metastasis, PNI, and pain. It is further determined that TrkA knockdown alone inhibits thermal hyperalgesia, whereas NGFR knockdown alone inhibits mechanical allodynia. Collectively the results highlight the ability of OSCC to co-opt different components of the neurotrophin pathway in metastasis, PNI, and pain.

Schwann Cells Induce Phenotypic Changes in Oral Cancer Cells.

Head and neck cancer (HNC) is the seventh most common cancer worldwide, the majority being oral squamous cell carcinoma. Despite advances in cancer diagnosis and treatment, the survival rate of patients with HNC remains stagnant. The cancer-nerve interaction has been recognized as an important driver of cancer progression. Schwann cells, a type of peripheral glia, have been implicated in promoting cancer cell growth, migration, dispersion, and invasion into the nerve in many cancers. Here, it is demonstrated that the presence of Schwann cells makes oral cancer cells more aggressive by promoting their proliferation, extracellular matrix breakdown, and altering cell metabolism. Furthermore, oral cancer cells became larger, more circular, with more projections and nuclei following co-culturing with Schwann cells. RNA-sequencing analysis in oral cancer cells following exposure to Schwann cells shows corresponding changes in genes involved in the hallmarks of cancer and cell metabolism; the enriched KEGG pathways are spliceosome, RNA transport, cell cycle, axon guidance, signaling pathways regulating pluripotency of stem cells, cAMP signaling, WNT signaling, proteoglycans in cancer and PI3K-Akt signaling. Taken together, these results suggest a significant role for Schwann cells in facilitating oral cancer progression, highlighting their potential as a target to treat oral cancer progression.

Brush swab as a noninvasive surrogate for tissue biopsies in epigenomic profiling of oral cancer.

BACKGROUND: Oral squamous cell carcinoma (OSCC) has poor survival rates. There is a pressing need to develop more precise risk assessment methods to tailor clinical treatment. Epigenome-wide association studies in OSCC have not produced a viable biomarker. These studies have relied on methylation array platforms, which are limited in their ability to profile the methylome. In this study, we use MethylCap-Seq (MC-Seq), a comprehensive methylation quantification technique, and brush swab samples, to develop a noninvasive, readily translatable approach to profile the methylome in OSCC patients. METHODS: Three OSCC patients underwent collection of cancer and contralateral normal tissue and brush swab biopsies, totaling 4 samples for each patient. Epigenome-wide DNA methylation quantification was performed using the SureSelectXT Methyl-Seq platform. DNA quality and methylation site resolution were compared between brush swab and tissue samples. Correlation and methylation value difference were determined for brush swabs vs. tissues for each respective patient and site (i.e., cancer or normal). Correlations were calculated between cancer and normal tissues and brush swab samples for each patient to determine the robustness of DNA methylation marks using brush swabs in clinical biomarker studies. RESULTS: There were no significant differences in DNA yield between tissue and brush swab samples. Mapping efficiency exceeded 90% across all samples, with no differences between tissue and brush swabs. The average number of CpG sites with at least 10x depth of coverage was 2,716,674 for brush swabs and 2,903,261 for tissues. Matched tissue and brush swabs had excellent correlation (r = 0.913 for cancer samples and r = 0.951 for normal samples). The methylation profile of the top 1000 CpGs was significantly different between cancer and normal samples (mean p-value = 0.00021) but not different between tissues and brush swabs (mean p-value = 0.11). CONCLUSIONS: Our results demonstrate that MC-Seq is an efficient platform for epigenome profiling in cancer biomarker studies, with broader methylome coverage than array-based platforms. Brush swab biopsy provides adequate DNA yield for MC-Seq, and taken together, our findings set the stage for development of a non-invasive methylome quantification technique for oral cancer with high translational potential.

Advances in Tissue Engineering and Implications for Oral and Maxillofacial Reconstruction.

BACKGROUND: Reconstructive surgery in the oral and maxillofacial region poses many challenges due to the complexity of the facial skeleton and the presence of composite defects involving soft tissue, bone and nerve defects. METHODS: Current methods of reconstruction include autologous grafting techniques with local or regional rotational flaps or microvascular free flaps, allografts, xenografts and prosthetic devices. RESULTS: Tissue engineering therapies utilizing stem cells provide promise for enhancing the current reconstructive options. CONCLUSIONS: This article is a review on tissue engineering strategies applicable to specialists who treat oral and maxillofacial defects. PRACTICAL IMPLICATIONS: We review advancements in hard tissue regeneration for dental rehabilitation, soft tissue engineering, nerve regeneration and innovative strategies for reconstruction of major defects.

The REASON score: an epigenetic and clinicopathologic score to predict risk of poor survival in patients with early stage oral squamous cell carcinoma.

BACKGROUND: Oral squamous cell carcinoma (OSCC) is a capricious cancer with poor survival rates, even for early-stage patients. There is a pressing need to develop more precise risk assessment methods to appropriately tailor clinical treatment. Genome-wide association studies have not produced a viable biomarker. However, these studies are limited by using heterogeneous cohorts, not focusing on methylation although OSCC is a heavily epigenetically-regulated cancer, and not combining molecular data with clinicopathologic data for risk prediction. In this study we focused on early-stage (I/II) OSCC and created a risk score called the REASON score, which combines clinicopathologic characteristics with a 12-gene methylation signature, to predict the risk of 5-year mortality. METHODS: We combined data from an internal cohort (n = 515) and The Cancer Genome Atlas (TCGA) cohort (n = 58). We collected clinicopathologic data from both cohorts to derive the non-molecular portion of the REASON score. We then analyzed the TCGA cohort DNA methylation data to derive the molecular portion of the risk score. RESULTS: 5-year disease specific survival was 63% for the internal cohort and 86% for the TCGA cohort. The clinicopathologic features with the highest predictive ability among the two the cohorts were age, race, sex, tobacco use, alcohol use, histologic grade, stage, perineural invasion (PNI), lymphovascular invasion (LVI), and margin status. This panel of 10 non-molecular features predicted 5-year mortality risk with a concordance (c)-index = 0.67. Our molecular panel consisted of a 12-gene methylation signature (i.e., HORMAD2, MYLK, GPR133, SOX8, TRPA1, ABCA2, HGFAC, MCPH1, WDR86, CACNA1H, RNF216, CCNJL), which had the most significant differential methylation between patients who survived vs. died by 5 years. All 12 genes have already been linked to survival in other cancers. Of the genes, only SOX8 was previously associated with OSCC; our study was the first to link the remaining 11 genes to OSCC survival. The combined molecular and non-molecular panel formed the REASON score, which predicted risk of death with a c-index = 0.915. CONCLUSIONS: The REASON score is a promising biomarker to predict risk of mortality in early-stage OSCC patients. Validation of the REASON score in a larger independent cohort is warranted.

Targeting the endothelin axis as a therapeutic strategy for oral cancer metastasis and pain.

Metastasis reduces survival in oral cancer patients and pain is their greatest complaint. We have shown previously that oral cancer metastasis and pain are controlled by the endothelin axis, which is a pathway comprised of the endothelin A and B receptors (ETAR and ETBR). In this study we focus on individual genes of the pathway, demonstrating that the endothelin axis genes are methylated and dysregulated in cancer tissue. Based on these findings in patients, we hypothesize that ETAR and ETBR play dichotomous roles in oral carcinogenesis and pain, such that ETAR activation and silenced ETBR expression result in increased carcinogenesis and pain. We test a treatment strategy that targets the dichotomous functions of the two receptors by inhibiting ETAR with macitentan, an ETAR antagonist approved for treatment of pulmonary hypertension, and re-expressing the ETBR gene with adenovirus transduction, and determine the treatment effect on cancer invasion (i.e., metastasis), proliferation and pain in vitro and in vivo. We demonstrate that combination treatment of macitentan and ETBR gene therapy inhibits invasion, but not proliferation, in cell culture and in a mouse model of tongue cancer. Furthermore, the treatment combination produces an antinociceptive effect through inhibition of endothelin-1 mediated neuronal activation, revealing the analgesic potential of macitentan. Our treatment approach targets a pathway shown to be dysregulated in oral cancer patients, using gene therapy and repurposing an available drug to effectively treat both oral cancer metastasis and pain in a preclinical model.

Transoral robotic surgery and neck dissection for HPV-positive oropharyngeal carcinoma: Importance of nodal count in survival.

BACKGROUND: In this study we determine the survival in patients with HPV-positive oropharyngeal carcinoma treated with transoral robotic surgery (TORS), neck dissection and risk-adapted adjuvant therapy. METHODS: We retrospectively identified 122 patients with HPV-positive oropharyngeal carcinoma treated with TORS and neck dissection between 2011 and 2018. Survival probability was calculated. We determined the effect of the type of neck dissection performed (modified radical neck dissection-MRND vs. selective neck dissection - SND), extranodal extension (ENE), margin status, and presence of ≥ 5 metastatic nodes on survival. RESULTS: Our patient population had a five-year overall survival of 91.0% (95% C.I. 85-97%). The five-year probability of recurrence or cancer-associated death was 0.0977 (95% C.I. 0.0927-0.1027). The five-year probability of cancer-associated death was 0.0528 (95% C.I. 0.048-0.0570). All patients who died of their disease had distant metastasis. Our PEG dependence rate was 0%. Patients with ENE and positive margins who underwent adjuvant chemoradiation did not have worse survival. Presence of ≥ 5 metastatic nodes portended worse survival after controlling for age, positive ENE and margins. Low yield (<18 nodes) on neck dissection worsened DFS on multivariable analysis. Furthermore, patients who underwent SND did not have worse OS than those who underwent MRND. CONCLUSION: Our study demonstrates that surgery could be simplified by performing TORS with SND rather than MRND. The one true poor prognostic factor in HPV-positive oropharyngeal carcinoma patients who undergo surgery is high nodal burden. Patients with high nodal burden are much more likely to die from their disease.

Anti-cancer and analgesic effects of resolvin D2 in oral squamous cell carcinoma.

Oral cancer is often painful and lethal. Oral cancer progression and pain may result from shared pathways that involve unresolved inflammation and elevated levels of pro-inflammatory cytokines. Resolvin D-series (RvDs) are endogenous lipid mediators derived from omega-3 fatty acids that exhibit pro-resolution and anti-inflammatory actions. These mediators have recently emerged as a novel class of therapeutics for diseases that involve inflammation; the specific roles of RvDs in oral cancer and associated pain are not defined. The present study investigated the potential of RvDs (RvD1 and RvD2) to treat oral cancer and alleviate oral cancer pain. We found down-regulated mRNA levels of GPR18 and GPR32 (which code for receptors RvD1 and RvD2) in oral cancer cells. Both RvD1 and RvD2 inhibited oral cancer proliferation in vitro. Using two validated mouse oral squamous cell carcinoma xenograft models, we found that RvD2, the more potent anti-inflammatory lipid mediator, significantly reduced tumor size. The mechanism of this action might involve suppression of IL-6, C-X-C motif chemokine 10 (CXCL10), and reduction of tumor necrosis. RvD2 generated short-lasting analgesia in xenograft cancer models, which coincided with decreased neutrophil infiltration and myeloperoxidase activity. Using a cancer supernatant model, we demonstrated that RvD2 reduced cancer-derived cytokines/chemokines (TNF-α, IL-6, CXCL10, and MCP-1), cancer mediator-induced CD11b+Ly6G- myeloid cells, and nociception. We infer from our results that manipulation of the endogenous pro-resolution pathway might provide a novel approach to improve oral cancer and cancer pain treatment.

Cutaneous pigmentation modulates skin sensitivity via tyrosinase-dependent dopaminergic signalling.

We propose a new mechanism of sensory modulation through cutaneous dopaminergic signalling. We hypothesize that dopaminergic signalling contributes to differential cutaneous sensitivity in darker versus lighter pigmented humans and mouse strains. We show that thermal and mechanical cutaneous sensitivity is pigmentation dependent. Meta-analyses in humans and mice, along with our own mouse behavioural studies, reveal higher thermal sensitivity in pigmented skin relative to less-pigmented or albino skin. We show that dopamine from melanocytes activates the D1-like dopamine receptor on primary sensory neurons. Dopaminergic activation increases expression of the heat-sensitive TRPV1 ion channel and reduces expression of the mechanically-sensitive Piezo2 channel; thermal threshold is lower and mechanical threshold is higher in pigmented skin.

Alterations in opioid inhibition cause widespread nociception but do not affect anxiety-like behavior in oral cancer mice.

Widespread pain and anxiety are commonly reported in cancer patients. We hypothesize that cancer is accompanied by attenuation of endogenous opioid-mediated inhibition, which subsequently causes widespread pain and anxiety. To test this hypothesis we used a mouse model of oral squamous cell carcinoma (SCC) in the tongue. We found that mice with tongue SCC exhibited widespread nociceptive behaviors in addition to behaviors associated with local nociception that we reported previously. Tongue SCC mice exhibited a pattern of reduced opioid receptor expression in the spinal cord; intrathecal administration of respective mu (MOR), delta (DOR), and kappa (KOR) opioid receptor agonists reduced widespread nociception in mice, except for the fail flick assay following administration of the MOR agonist. We infer from these findings that opioid receptors contribute to widespread nociception in oral cancer mice. Despite significant nociception, mice with tongue SCC did not differ from sham mice in anxiety-like behaviors as measured by the open field assay and elevated maze. No significant differences in c-Fos staining were found in anxiety-associated brain regions in cancer relative to control mice. No correlation was found between nociceptive and anxiety-like behaviors. Moreover, opioid receptor agonists did not yield a statistically significant effect on behaviors measured in the open field and elevated maze in cancer mice. Lastly, we used an acute cancer pain model (injection of cancer supernatant into the mouse tongue) to test whether adaptation to chronic pain is responsible for the absence of greater anxiety-like behavior in cancer mice. No changes in anxiety-like behavior were observed in mice with acute cancer pain.

OPRM1 Methylation Contributes to Opioid Tolerance in Cancer Patients.

Cancer patients in pain require high doses of opioids and quickly become opioid-tolerant. Previous studies have shown that chronic cancer pain as well as high-dose opioid use lead to mu-opioid receptor downregulation. In this study we explore downregulation of the mu-opioid receptor gene (OPRM1), as a mechanism for opioid tolerance in the setting of opioid use for cancer pain. We demonstrate in a cohort of 84 cancer patients that high-dose opioid use correlates with OPRM1 hypermethylation in peripheral leukocytes of these patients. We then reverse-translate our clinical findings by creating a mouse cancer pain model; we create opioid tolerance in the mouse cancer model to mimic opioid tolerance in the cancer patients. Using this model we determine the functional significance of OPRM1 methylation on cancer pain and opioid tolerance. We focus on 2 main cells within the cancer microenvironment: the cancer cell and the neuron. We show that targeted re-expression of mu-opioid receptor on cancer cells inhibits mechanical and thermal hypersensitivity, and prevents opioid tolerance, in the mouse model. The resultant analgesia and protection against opioid tolerance are likely due to preservation of mu-opioid receptor expression on the cancer-associated neurons. PERSPECTIVE: We demonstrate that epigenetic regulation of OPRM1 contributes to opioid tolerance in cancer patients, and that targeted gene therapy could treat cancer-induced nociception and opioid tolerance in a mouse cancer model.

Ex vivo nonviral gene delivery of µ-opioid receptor to attenuate cancer-induced pain.

Virus-mediated gene delivery shows promise for the treatment of chronic pain. However, viral vectors have cytotoxicity. To avoid toxicities and limitations of virus-mediated gene delivery, we developed a novel nonviral hybrid vector: HIV-1 Tat peptide sequence modified with histidine and cysteine residues combined with a cationic lipid. The vector has high transfection efficiency with little cytotoxicity in cancer cell lines including HSC-3 (human tongue squamous cell carcinoma) and exhibits differential expression in HSC-3 (∼45-fold) relative to HGF-1 (human gingival fibroblasts) cells. We used the nonviral vector to transfect cancer with OPRM1, the µ-opioid receptor gene, as a novel method for treating cancer-induced pain. After HSC-3 cells were transfected with OPRM1, a cancer mouse model was created by inoculating the transfected HSC-3 cells into the hind paw or tongue of athymic mice to determine the analgesic potential of OPRM1 transfection. Mice with HSC-3 tumors expressing OPRM1 demonstrated significant antinociception compared with control mice. The effect was reversible with local naloxone administration. We quantified ß-endorphin secretion from HSC-3 cells and showed that HSC-3 cells transfected with OPRM1 secreted significantly more ß-endorphin than control HSC-3 cells. These findings indicate that nonviral delivery of the OPRM1 gene targeted to the cancer microenvironment has an analgesic effect in a preclinical cancer model, and nonviral gene delivery is a potential treatment for cancer pain.

Oral mucosal injury caused by mammalian target of rapamycin inhibitors: emerging perspectives on pathobiology and impact on clinical practice.

In recent years oral mucosal injury has been increasingly recognized as an important toxicity associated with mammalian target of rapamycin (mTOR) inhibitors, including in patients with breast cancer who are receiving everolimus. This review addresses the state-of-the-science regarding mTOR inhibitor-associated stomatitis (mIAS), and delineates its clinical characteristics and management. Given the clinically impactful pain associated with mIAS, this review also specifically highlights new research focusing on the study of the molecular basis of pain. The incidence of mIAS varies widely (2-78%). As reported across multiple mTOR inhibitor clinical trials, grade 3/4 toxicity occurs in up to 9% of patients. Managing mTOR-associated oral lesions with topical oral, intralesional, and/or systemic steroids can be beneficial, in contrast to the lack of evidence supporting steroid treatment of oral mucositis caused by high-dose chemotherapy or radiation. However, steroid management is not uniformly efficacious in all patients receiving mTOR inhibitors. Furthermore, technology does not presently exist to permit clinicians to predict a priori which of their patients will develop these lesions. There thus remains a strategic need to define the pathobiology of mIAS, the molecular basis of pain, and risk prediction relative to development of the clinical lesion. This knowledge could lead to novel future interventions designed to more effectively prevent mIAS and improve pain management if clinically significant mIAS lesions develop.