CNSC-61. NEURONAL-ACTIVITY DEPENDENT MECHANISMS OF SMALL CELL LUNG CANCER PATHOGENESIS

Abstract Neural activity is increasingly recognized as a crucial regulator of cancer growth. In the brain, neuronal activity robustly influences glioma growth both through paracrine mechanisms and through electrochemical integration of malignant cells into neural circuitry via neuron-to-glioma synapses. Outside of the CNS, innervation of tumors such as prostate, breast, pancreatic, and gastrointestinal cancers by peripheral nerves similarly regulates cancer progression. However, the extent to which the nervous system regulates lung cancer progression, either in the lung or when metastatic to the brain, is less well understood. Small cell lung cancer (SCLC) is a lethal high-grade neuroendocrine tumor that exhibits a strong propensity to metastasize to the brain. Here we demonstrate that SCLC cells in the brain co-opt neuronal activity-regulated mechanisms to stimulate growth and progression. With in vivo optogenetic stimulation, we show that glutamatergic and GABAergic cortical neuronal activity each drive proliferation of SCLC through both paracrine and synaptic neuron-cancer interactions. In the brain, SCLC cells form bona fide neuron-to-SCLC synapses evident on immunoelectron microscopy for the first time for non-brain derived malignancy. Using electrophysiology and two-photon calcium imaging, we find that SCLC cells exhibit depolarizing currents with consequent calcium transients in response to neuronal activity. SCLC cell membrane depolarization is sufficient to promote the growth of intracranial tumors. We also demonstrate reciprocal effects of SCLC on neurons, manifesting as increased neuronal synaptogenesis and elevated field potentials in regions of the tumor. Finally, in the lung, vagus nerve transection markedly inhibits primary lung tumor formation and development and awards survival benefit in spontaneous genetic SCLC model, highlighting a critical role for innervation in overall SCLC growth. Taken together, these studies illustrate that neuronal activity plays a crucial role in dictating SCLC pathogenesis in both the lung and the brain.