Faculty Bibliography

Cancer patients often suffer from pain and most will be prescribed mu-opioids. mu-opioids are not satisfactory in treating cancer pain and are associated with multiple debilitating side effects. Recent studies show that mu and delta opioid receptors are separately expressed on IB4 (-) and IB4 (+) neurons, which control thermal and mechanical pain, respectively. In this study we investigated IB4 (+) and IB4 (-) neurons in mechanical and thermal hypersensitivity in an orthotopic mouse oral cancer model. We used a delta opioid receptor agonist and a P2X(3) antagonist to target IB4 (+) neurons and to demonstrate that this subset plays a key role in cancer-induced mechanical allodynia, but not in thermal hyperalgesia. Moreover, selective removal of IB4 (+) neurons using IB4-saporin impacts cancer-induced mechanical but not thermal hypersensitivity. Our results demonstrate that peripherally administered pharmacological agents targeting IB4 (+) neurons, such as a selective delta-opioid receptor agonist or P2X(3) antagonist, might be useful in treating oral cancer pain. PERSPECTIVE: To clarify the mechanisms of oral cancer pain, we examined the differential role of IB4 (+) and IB4 (-) neurons. Characterization of these 2 subsets of putative nociceptors is important for further development of effective clinical cancer pain relief.

PURPOSE: We present a strategy to survey proteolytic processes that occur in human cancer microenvironments. EXPERIMENTAL DESIGN: In situ microdialysis during oral cancer surgery was combined with mass spectrometry-based proteomics to analyze interstitial fluid surrounding tumors and anatomically matched normal sites. Protease activity-based (18)O-profiling was utilized to reveal peptides that were processed by co-collected proteases ex vivo. RESULTS: We demonstrated for the first time the use of microdialysis in humans to collect interstitial fluid from cancer microenvironments. Proteomic profiling identified proteases and inhibitors in the microdialysis samples. A subset of peptides displayed characteristic (18)O-isotope patterns that indicated processing by endogenous proteases. CONCLUSIONS AND CLINICAL RELEVANCE: The presented approach provides unprecedented views of in vivo targets of proteases without disrupting the cancer or surrounding tissue. The methodology can be broadly adapted to other physiological conditions in which proteolytic mediators are involved (e.g. arthritic joints, inflamed muscle, other types of cancer) and where a comparison of normal and pathological tissue is sought.

Cancers often cause excruciating pain and rapid weight loss, severely reducing quality of life in cancer patients. Cancer-induced pain and cachexia are often studied and treated independently, although both symptoms are strongly linked with chronic inflammation and sustained production of proinflammatory cytokines. Because nerve growth factor (NGF) plays a cardinal role in inflammation and pain, and because it interacts with multiple proinflammatory cytokines, we hypothesized that NGF acts as a key endogenous molecule involved in the orchestration of cancer-related inflammation. NGF might be a molecule common to the mechanisms responsible for clinically distinctive cancer symptoms such as pain and cachexia as well as cancer progression. Here we reported that NGF was highly elevated in human oral squamous cell carcinoma tumors and cell cultures. Using two validated mouse cancer models, we further showed that NGF blockade decreased tumor proliferation, nociception, and weight loss by orchestrating proinflammatory cytokines and leptin production. NGF blockade also decreased expression levels of nociceptive receptors TRPV1, TRPA1, and PAR-2. Together, these results identified NGF as a common link among proliferation, pain, and cachexia in oral cancer. Anti-NGF could be an important mechanism-based therapy for oral cancer and its related symptoms

Rodent pain models play an important role in understanding the mechanisms of nociception and have accelerated the search for new treatment approaches for pain. Creating an objective metric for orofacial nociception in these models presents significant technical obstacles. No animal assay accurately measures pain-induced orofacial dysfunction that is directly comparable to human orofacial dysfunction. We developed and validated a high throughput, objective, operant, nociceptive animal assay, and an instrument to perform the assay termed the dolognawmeter, for evaluation of conditions known to elicit orofacial pain in humans. Using the device our assay quantifies gnawing function in the mouse. We quantified a behavioral index of nociception and demonstrated blockade of nociception in three models of orofacial pain: (1) TMJ inflammation, (2) masticatory myositis, and (3) head and neck cancer. This assay will be useful in the study of nociceptive mediators involved in the development and progression of orofacial pain conditions and it will also provide a unique tool for development and assessment of new therapeutic approaches

In this study we investigated the role of endothelin-1 (ET-1) and its peripheral receptor (ET-A) in carcinoma-induced pain in a mouse cancer pain model. Tumors were induced in the hind paw of female mice by local injection of cells derived from a human oral squamous cell carcinoma (SCC). Significant pain, as indicated by reduction in withdrawal thresholds in response to mechanical stimulation, began at four days after SCC inoculation and lasted to 28 days, the last day of measurement. Intra-tumor expression of both ET-1 mRNA and ET-1 protein were significantly upregulated compared to normal tissue, and local administration of the ET-A receptor selective antagonist, BQ-123 (100 microM) significantly elevated withdrawal thresholds, indicating the induction of an antinociceptive effect. These findings support the suggestion that ET-1 and ET-A receptors contribute to the severity of carcinoma-induced soft tissue cancer pain