Reciprocal interactions between cancer and Schwann cells contribute to oral cancer progression and pain

Abstract

Pain associated with oral squamous cell carcinoma (oral SCC) decreases quality of life and survival. The interaction between cancer and the peripheral nerves is known to initiate and amplify pain and contribute to carcinogenesis. Schwann cells envelop peripheral nerves and are activated in response to neuronal damage. The contributions of Schwann cells to oral SCC progression and pain are unknown. Using a non-contact co-culture model, we demonstrate that Schwann cells (RSC-96) and oral SCC cells (HSC-3) reciprocally interact to promote proliferation, migration, and invasion. Schwann cell-oral SCC interaction leads to increased production of adenosine, which stimulates cell proliferation and migration of both cell types. The adenosine receptor A2B ( ADORA2B ) is expressed on RSC-96 cells. We show that supernatant from the RSC-96 cells co-cultured with HSC-3 cells induces increased mechanical hypersensitivity in mice compared to supernatant from control RSC-96 cells. Treatment with the ADORA2B antagonist PSB603 significantly inhibits co-culture interactions - proliferation and migration, and co-culture supernatant induced mechanical hypersensitivity. RSC-96 cells co-cultured with HSC-3 cells secrete increased amounts of the pronociceptive mediator, interleukin-6 (IL-6), which can be reduced by adding PSB603 into the co-culture. Our data support a reciprocal interaction between oral SCC and Schwann cells mediated by adenosine with potential to promote oral SCC progression and pain via increased secretion of IL-6.

TNFα promotes oral cancer growth, pain, and Schwann cell activation

“…We have previously demonstrated that rat Schwann cells (RSC-96) and human oral SCC cells (HSC-3) reciprocally interact to promote proliferation, migration, and invasion 11 . Here we found that human Schwann cells increased migration and proliferation in the presence of human oral cancer cells as well; the growth rate of human Schwann cells was increased in the presence of either precancer dysplastic oral keratinocytes (DOK) or HSC-3 cells grown in culture inserts ( P < 0.001, Fig.…”

“…Blocking JNK that is upstream of c-Jun activation 61 is also effective in pain relief in our mouse paw xenograft model. Cancer- or hypoxia-activated Schwann cells release nociceptive mediators such as IL-6, TNFα, CXCL2, and IL-8 11 , 15 ; these mediators could sensitize primary afferent neurons to cause pain. Schwann cell activation causes myelin breakdown 41 ; the loss of structural support and insulation by myelin sheath breakdown is another possible explanation of pain produced by activated Schwann cells.…”

“…Cell migration assays were performed using transwell Boyden chambers with an 8 µm pore size according to the manufacturer’s instructions (Corning) and our published protocols 11 . To examine Schwann cell migration towards HSC-3 cells, 1.0 × 10 4 Schwann cells were seeded on the migration chambers; 1.0 × 10 4 HSC-3 cells were seeded in the bottom chamber.…”

“…For the hypoxia experiments, Schwann cells were added to the top chamber and SCM containing 10% FBS was added to the bottom chamber. After 24 h incubation, the non-migrating cells were removed, and membranes containing migrated cells were fixed and stained with Diff-Quik (Microptic) 11 . The number of migrating cells on the lower side of the membrane was counted under a Nikon Eclipse TI microscope.…”

“…One such mediator is TNFα, a “master regulator” cytokine that initiates inflammation and drives pro-inflammatory cytokine cascades 10 . Many cytokines downstream of TNFα, such as nerve growth factor (NGF) and interleukin 6 (IL-6), have been implicated in oral cancer pain 8 , 9 , 11 . We found that TNFα is secreted from oral cancer cell lines and upregulated in cancer tongue tissues collected from mice treated with the carcinogen 4-nitroquinoline 1-oxide (4NQO) 9 .…”