Dense tumor innervation is associated with enhanced cancer progression and poor prognosis. We observed innervation in breast, prostate, pancreatic, lung, liver, ovarian, and colon cancers. Defining innervation in high-grade serous ovarian carcinoma (HGSOC) was a focus since sensory innervation was observed whereas the normal tissue contains predominantly sympathetic input. The origin, specific nerve type, and the mechanisms promoting innervation and driving nerve-cancer cell communications in ovarian cancer remain largely unknown. The technique of neuro-tracing enhances the study of tumor innervation by offering a means for identification and mapping of nerve sources that may directly and indirectly affect the tumor microenvironment. Here, we establish a murine model of HGSOC and utilize image-guided microinjections of retrograde neuro-tracer to label tumor-infiltrating peripheral neurons, mapping their source and circuitry. We show that regional sensory neurons innervate HGSOC tumors. Interestingly, the axons within the tumor trace back to local dorsal root ganglia as well as jugular–nodose ganglia. Further manipulations of these tumor projecting neurons may define the neuronal contributions in tumor growth, invasion, metastasis, and responses to therapeutics.

Sigma non-opioid intracellular receptor 1 (Sigma-1R) is an intracellular chaperone protein residing on the endoplasmic reticulum at the mitochondrial-associated membrane (MAM) region. Sigma-1R is abundant in the brain and is involved in several physiological processes as well as in various disease states. The role of Sigma-1R at the blood–brain barrier (BBB) is incompletely characterized. In this study, the effect of Sigma-1R activation was investigated in vitro on rat brain microvascular endothelial cells (RBMVEC), an important component of the blood–brain barrier (BBB), and in vivo on BBB permeability in rats. The Sigma-1R agonist PRE-084 produced a dose-dependent increase in mitochondrial calcium, and mitochondrial and cytosolic reactive oxygen species (ROS) in RBMVEC. PRE-084 decreased the electrical resistance of the RBMVEC monolayer, measured with the electric cell-substrate impedance sensing (ECIS) method, indicating barrier disruption. These effects were reduced by pretreatment with Sigma-1R antagonists, BD 1047 and NE 100. In vivo assessment of BBB permeability in rats indicates that PRE-084 produced a dose-dependent increase in brain extravasation of Evans Blue and sodium fluorescein brain; the effect was reduced by the Sigma-1R antagonists. Immunocytochemistry studies indicate that PRE-084 produced a disruption of tight and adherens junctions and actin cytoskeleton. The brain microcirculation was directly visualized in vivo in the prefrontal cortex of awake rats with a miniature integrated fluorescence microscope (aka, miniscope; Doric Lenses Inc.). Miniscope studies indicate that PRE-084 increased sodium fluorescein extravasation in vivo. Taken together, these results indicate that Sigma-1R activation promoted oxidative stress and increased BBB permeability.

Omega-3 polyunsaturated fatty acids (n-3 PUFAs), obtained from diet and dietary supplements, have been tested in clinical trials for the prevention or treatment of several diseases. n-3 PUFAs exert their effects by activation of free fatty acid (FFA) receptors. FFA1 receptor, expressed in the pancreas and brain, is activated by medium- to long-chain fatty acids. Despite some beneficial effects on cognition, the effects of n-3 PUFAs on the blood–brain barrier (BBB) are not clearly understood. We examined the effects of FFA1 activation on BBB permeability in vitro, using rat brain microvascular endothelial cells (RBMVEC), and in vivo, by assessing Evans Blue extravasation and by performing live imaging of brain microcirculation in adult rats. AMG837, a synthetic FFA1 agonist, produced a dose-dependent decrease in RBMVEC monolayer resistance assessed with Electric Cell–Substrate Impedance Sensing (ECIS); the effect was attenuated by the FFA1 antagonist, GW1100. Immunofluorescence studies revealed that AMG837 produced a disruption in tight and adherens junction proteins. AMG837 increased Evans Blue content in the rat brain in a dose-dependent manner. Live imaging studies of rat brain microcirculation with miniaturized fluorescence microscopy (miniscope) showed that AMG837 increased extravasation of sodium fluorescein. Taken together, our results demonstrate that FFA1 receptor activation reduced RBMVEC barrier function and produced a transient increase in BBB permeability.

Orexin A, an endogenous peptide involved in several functions including reward, acts via activation of orexin receptors OX₁ and OX₂, Gq-coupled GPCRs. We examined the effect of a selective OX₁ agonist, OXA (17-33) on cytosolic calcium concentration, [Ca²⁺]_i, in neurons of nucleus accumbens, an important area in the reward circuit. OXA (17-33) increased [Ca²⁺]_i in a dose-dependent manner; the effect was prevented by SB-334867, a selective OX₁ receptors antagonist. In Ca²⁺-free saline, the OXA (17-33)-induced increase in [Ca²⁺]_i was not affected by pretreatment with bafilomycin A1, an endo-lysosomal calcium disrupter, but was blocked by 2-APB and xestospongin C, antagonists of inositol-1,4,5-trisphosphate (IP₃) receptors. Pretreatment with VU0155056, PLD inhibitor, or BD-1047 and NE-100, Sigma-1R antagonists, reduced the [Ca²⁺]_i response elicited by OXA (17-33). Cocaine potentiated the increase in [Ca²⁺]_i by OXA (17-33); the potentiation was abolished by Sigma-1R antagonists. Our results support an additional signaling mechanism for orexin A-OX₁ via choline-Sigma-1R and a critical role for Sigma-1R in the cocaine–orexin A interaction in nucleus accumbens neurons.

Peripheral solid malignancies are infiltrated by nerves. Using syngeneic cell lines, we set out to define whether sex influences tumor innervation in oral cancers and melanoma. Tumors grew significantly slower in females and were significantly more innervated than in males. In oral cancer, tumor-infiltrating nerves connect to a pre-existing neural circuit that enters the brain and impacts behavior. Thus, we evaluated the impact of sex on this circuit and assessed the behavioral consequences. We found no differences in the timing or extent of behavioral declines between oral tumor-bearing males and females. Moreover, in untreated mice, metastasis did not differ by sex. Treatment of oral tumors with cisplatin and radiation slowed tumor growth in male and female mice but significantly increased tumor innervation with females harboring the greatest innervation density. Treated females also harbored significantly increased metastases in their lungs compared to treated males. Treatment improved tumor-associated behavioral changes. While the tumor-brain circuit did not differ between males and females, the activation status of neurons and glia in projection areas significantly increased on the ipsilateral side. This heightened activation was attenuated following cisplatin/radiation treatment. These studies indicate that peripheral malignancies activate neurons and glia in central nervous system (CNS) projection areas, and that standard-of-care therapy attenuates this, which correlates with improved behavior. These findings emphasize that sex influences peripheral tumor-infiltrating nerves and brain function (via the tumor-brain circuit) and suggest that severing or silencing this circuit could improve patient outcomes.