Research
The Dougherty Lab examines mechanisms of chronic pain, including neuropathic pain related to metastasized cancer and chemotherapy-induced peripheral neuropathy. We conduct physiological, biochemical and anatomical studies using both rodent and human nervous tissue.
Using dorsal root ganglion (DRG) tissue for sensory neuron research
We have characterized paclitaxel-induced peripheral neuropathy using rodent models and have developed an in vitro model of chemotherapy-induced neuropathic pain model to study chemotherapy-related changes in cultured dorsal root ganglion (DRG) tissue. A unique aspect of our work is the ability to use human sensory neurons cultured from DRG collected during spinal surgery for metastatic tumor growth.
To bolster these studies, we have established procedures in collaboration with the Lifegift, an organ procurement organization operating in the Texas Medical Center, that enable us to collect human DRGs from organ donors in the OR within hours of cross clamp. This minimizes ischemic time and allows for culture of DRG neurons from patients without a history of cancer which provides ideal healthy control data for comparison studies with the MD Anderson patient population.
The Tissue Procurement and Processing Core
The initiation of donor DRG collection to complement our cancer patient DRGs directly contributed to our team being awarded a U19 grant in coordination with the human DRG and spinal cord tissue laboratories at The University of Texas at Dallas and University of Washington. This has enabled the creation of a Tissue Procurement and Processing Core to better facilitate large-scale projects with these limited human tissue resources.
Related collaborative projects are investigating novel approaches to reduce pathological spontaneous activity in human sensory neurons and attenuate sensitization in neurons from patients with neuropathic pain. These projects are currently funded under a multi-PI R01.
Current research with DRG tissue
Using DRG tissue from MD Anderson patients with and without neuropathic pain for RNA sequencing studies, we showed that DRGs from dermatomes with and without radiculopathy have significant sex differences in RNA expression associated with neuropathic pain. These results were published in Brain and are guiding our latest experiments in cultured human DRG neurons, including work with the cytokine oncostatin-M (OSM).
Upregulation of OSM and its receptor was identified in pain-associated DRGs, and we found that OSM decreases mechanical withdrawal thresholds in rats and sensitizes both rat and human DRG neurons in vitro. OSM is part of the IL-6 family, and we are also targeting signaling mechanisms downstream from these receptors, including the MNK1/2-eIF4E axis, which has been identified as a potential target for treatment based on its role in translational regulation in chronic pain states. We found that inhibition of MNK1/2 with Tomivosertib silences ectopic activity in human DRG neurons from pain-associated dermatomes.
A collaboration with University of California San Diego targets TLR4 lipid rafts associated with neuroinflammation. We are currently using the Brennan model of post-operative incisional pain in rats to test a novel TLR4 lipid raft-depleting compound (AIBP) and perform patch clamp electrophysiology studies in DRG neurons with ectopic activity. Successful depletion of these lipid rafts attenuated post-incision nociceptive behavior in rats and decreased spontaneous activity in sensitized rat and human DRG neurons. Based on these results, we were recently awarded a multi-PI R01 to pursue these studies.
Investigating cancer-neuron interactions
Work as part of an ongoing collaboration with Dr. Juan Cata has focused on the pro-inflammatory, pro-nociceptive microenvironment produced by human squamous cell carcinoma cells (FaDu) in vitro and how it can trigger sensitization of rat sensory neurons in co-culture. We identified differences in the robustness of this effect based on sex and age, with more evidence of sensitization among neurons from male and older adult rats.
Given that the median age of diagnosis in head and neck squamous cell carcinoma is 55-65 years old and that diagnoses for many types of head and neck cancers are heavily biased towards men, our findings provide a clinically relevant model of cancer-neuron interaction that can be used to explore both mechanisms and potential treatments for head and neck cancer pain.
Triggers for neuronal sensitization of human DRG neurons
Consistent with these findings, we also observed sensitization in small-diameter human DRG neurons after co-culture with FaDu cells, which strengthens the translational potential of our work. We published these findings in PAIN Reports.
We also found that cancer conditioned media or exosomes can also induce neuronal sensitization in cultured DRG neurons. We are exploring these mechanisms in depth as well as whether these effects are exclusive to head and neck cancers or are common to cancers known for their pro-inflammatory microenvironments, such as pancreatic adenocarcinoma. In addition, we are also exploring how exosomes released by cultured rodent DRG are altered in different experimental pain models, including chemotherapy-induced peripheral neuropathy and inflammatory pain.