Faculty Bibliography

Cancer pain sends a message. It is frightening to the patient. It heralds progression or recurrence to the oncologist. It is a biological readout of the cancer-nerve interaction for the scientist. Nerves have been considered bystanders within the cancer microenvironment. However, emerging information suggests that nerves are recruited and participate in the carcinogenic process. These newly formed fibers respond to mediators secreted by constituents of the cancer microenvironment. In this manner, these nerves serve as bellwethers and sensors embedded within the cancer. When we rigorously assess patients' cancer pain, we gain insight into the action of cancer. An enhanced understanding of cancer pain offers biological questions that if answered might not only provide relief from cancer pain but might also improve survival.

The pharmacological effect of opioids originates, at the cellular level, by their interaction with the mu-opioid receptor (mOR) resulting in the regulation of voltage-gated Ca2+ channels and inwardly rectifying K+ channels that ultimately modulate the synaptic transmission. Recently, an alternative six trans-membrane helix isoform of mOR, (6TM-mOR) has been identified, but its function and signaling are still largely unknown. Here, we present the structural and functional mechanisms of 6TM-mOR signaling activity upon binding to morphine. Our data suggest that despite the similarity of binding modes of the alternative 6TM-mOR and the dominant seven trans-membrane helix variant (7TM-mOR), the interaction with morphine generates different dynamic responses in the two receptors, thus, promoting the activation of different mOR-specific signaling pathways. We characterize a series of 6TM-mOR-specific cellular responses, and observed that they are significantly different from those for 7TM-mOR. Morphine stimulation of 6TM-mOR does not promote a cellular cAMP response, while it increases the intracellular Ca2+ concentration and reduces the cellular K+ conductance. Our findings indicate that 6TM-mOR has a unique contribution to the cellular opioid responses. Therefore, it should be considered as a relevant target for the development of novel pharmacological tools and medical protocols involving the use of opioids.

Interindividual variability exists in persistent breast pain following breast cancer surgery. Recently, we used growth mixture modeling to identify 3 subgroups of women (N = 398) with distinct persistent breast pain trajectories (ie, mild, moderate, severe) over 6 months following surgery. The purposes of this study were to identify demographic and clinical characteristics that differed among the breast pain classes and, using linear mixed effects modeling, to examine how changes over time and in sensitivity in the breast scar area, pain qualities, pain interference, and hand and arm function differed among these classes. Several demographic and clinical characteristics differentiated the breast pain classes. Of note, 60 to 80% of breast scar sites tested were much less sensitive than the unaffected breast. Significant group effects were observed for pain qualities and interference scores, such that, on average, women in the severe pain class reported higher scores than women in the moderate pain class. In addition, women in the moderate pain class reported higher scores than women in the mild pain class. Compared to women in the mild pain class, women in the severe pain class had significantly impaired grip strength, and women in the moderate and severe pain classes had impaired flexion and abduction. PERSPECTIVE: Subgroups of women with persistent postsurgical breast pain differed primarily with respect to the severity rather than the nature or underlying mechanisms of breast pain. Pervasive sensory loss and the association between persistent breast pain and sustained interference with function suggest the need for long-term clinical follow-up.

The global burden of cancer pain is enormous and opioids, despite their side effects, remain the primary therapeutic approach. The cause of cancer pain is unknown. Mechanisms driving cancer pain differ from those mechanisms responsible for inflammatory and neuropathic pain. The prevailing hypothesis put forward to explain cancer pain posits that cancers generate and secrete mediators which sensitize and activate primary afferent nociceptors in the cancer microenvironment. Moreover, cancers induce neurochemical reorganization of the spinal cord, which contributes to spontaneous activity and enhanced responsiveness. The purpose of this review, which covers clinical and preclinical studies, is to highlight those peripheral and central mechanisms responsible for cancer pain. The challenges facing neuroscientists and clinicians studying and ultimately treating cancer pain are discussed.

PURPOSE: In this study, we evaluated the analgesic potential of demethylating drugs on oral cancer pain. Although demethylating drugs could affect expression of many genes, we focused on the mu-opioid receptor (OPRM1) gene pathway, because of its role in pain processing. We determined the antinociceptive effect of OPRM1 re-expression in a mouse oral cancer model. EXPERIMENTAL DESIGN: Using a mouse oral cancer model, we determined whether demethylating drugs produced antinociception through re-expression of OPRM1. We then re-expressed OPRM1 with adenoviral transduction and determined if, and by what mechanism, OPRM1 re-expression produced antinociception. To determine the clinical significance of OPRM1 on cancer pain, we quantified OPRM1 methylation in painful cancer tissues and nonpainful contralateral normal tissues of patients with oral cancer, and nonpainful dysplastic tissues of patients with oral dysplasia. RESULTS: We demonstrated that OPRM1 was methylated in cancer tissue, but not normal tissue, of patients with oral cancer, and not in dysplastic tissues from patients with oral dysplasia. Treatment with demethylating drugs resulted in mechanical and thermal antinociception in the mouse cancer model. This behavioral change correlated with OPRM1 re-expression in the cancer and associated neurons. Similarly, adenoviral-mediated OPRM1 re-expression on cancer cells resulted in naloxone-reversible antinociception. OPRM1 re-expression on oral cancer cells in vitro increased beta-endorphin secretion from the cancer, and decreased activation of neurons that were treated with cancer supernatant. CONCLUSION: Our study establishes the regulatory role of methylation in cancer pain. OPRM1 re-expression in cancer cells produces antinociception through cancer-mediated endogenous opioid secretion. Demethylating drugs have an analgesic effect that involves OPRM1.

BACKGROUND: Understanding normal volume asymmetry is essential for accurate assessment of limb volume changes following breast cancer (BC) treatment in which lymphatic function is disrupted. The purposes of this study were to evaluate for differences in dominant and nondominant limb volumes and to evaluate for interactions between the effects of dominance and side of cancer on limb volume. METHODS AND RESULTS: This study evaluated preoperative limb volumes of 397 women enrolled in a prospective, longitudinal study of neuropathic pain and lymphedema. Volume was calculated from circumference. Limb resistance was measured with bioimpedance. Women were dichotomized into two groups: those whose cancer was on their dominant side and those whose cancer was on their nondominant side. Analyses of variance were used to evaluate for differences. In 47%, BC occurred on the side of the dominant limb. Except for the 30 to 40 centimeter (cm) limb volume segment, a main effect of dominance was found for all measures. The volume of the dominant limb was significantly greater than that of the nondominant limb. No main effects were found for side of cancer. A statistically significant interaction was found only at the 0 to 10 cm limb volume segment. CONCLUSIONS: Prior to BC treatment, the dominant limb demonstrated lower bioimpedance resistance (-2.09%) and greater total limb volume (1.12%) than the nondominant limb. Segmental volume differences were greatest at the proximal forearm segment (2.31%) and least at the proximal arm segment (0.21%). This study provides evidence that preoperative volume assessment is important due to normal variability associated with limb dominance.

Oral mucositis is a significant problem in cancer patients treated with radiation or chemotherapy, often hindering definitive cancer treatment. For patients with oral mucositis, pain is the most distressing symptom, leading to loss of orofacial function and poor quality of life. While oral mucositis has been well-described, its pathophysiology is poorly understood. Oral health professionals treating patients with mucositis have almost no effective therapies to treat or prevent oral mucositis. The purpose of this review is to (1) describe the current preclinical models of oral mucositis and their contribution to the understanding of mucositis pathophysiology, (2) explore preclinical studies on therapies targeting mucositis and discuss the clinical trials that have resulted from these preclinical studies, and (3) describe the proposed pathophysiology of oral mucositis pain and preclinical modeling of oral mucositis pain.

BACKGROUND: A large amount of interindividual variability exists in the occurrence of symptoms in patients receiving chemotherapy (CTX). The purposes of the current study, which was performed in a sample of 582 oncology outpatients who were receiving CTX, were to identify subgroups of patients based on their distinct experiences with 25 commonly occurring symptoms and to identify demographic and clinical characteristics associated with subgroup membership. In addition, differences in quality of life outcomes were evaluated. METHODS: Oncology outpatients with breast, gastrointestinal, gynecological, or lung cancer completed the Memorial Symptom Assessment Scale before their next cycle of CTX. Latent class analysis was used to identify subgroups of patients with distinct symptom experiences. RESULTS: Three distinct subgroups of patients were identified (ie, 36.1% in Low class; 50.0% in Moderate class, and 13.9% in All High class). Patients in the All High class were significantly younger and more likely to be female and nonwhite, and had lower levels of social support, lower socioeconomic status, poorer functional status, and a higher level of comorbidity. CONCLUSIONS: Findings from the current study support the clinical observation that some oncology patients experience a differentially higher symptom burden during CTX. These high-risk patients experience significant decrements in quality of life. Cancer 2014. (c) 2014 American Cancer Society.