Background: Pancreatic cancer (PC) associated pain is debilitating and affects the efficacy of cancer treatments. Current therapies offer only transient relief, underscoring the need for novel mechanistic insights and therapeutic targets. Neural hypertrophy, neuritis (particularly mast cell infiltration), and fibrosis (via collagenous stroma secreted by pancreatic stellate cells, PSCs) are features of PC and are postulated to mediate pancreatic pain. Emerging evidence suggests that chemokines involved in pancreatic inflammation potentially contribute to the generation of pain.
Hypothesis: Pain in PC is driven by tumour-derived signals, particularly the secretion of the chemokine CXCL12 from activated PSCs interacting with CXCR4 receptors on mast cells and neuronal cells, triggering neuroinflammation and pain signalling.
This in vitro study aims to investigate the role of the CXCL12-CXCR4 axis in PSC-mast cell-neuronal cell interactions, as a potential target for inhibiting pain signals for PC.
Method: (i) Mouse PSCs were co-cultured with mast cells, and the expression of CXCR4 and CXCL12 was assessed by RT-PCR (n=3, 50.000 per cell type/well). (ii) Mouse PSCs, mast cells and Dorsal Root Ganglion (DRG) neurons (n=3, 50,000 per cell type/well) were co-cultured/incubated with CXCL12 inhibitor (200mM) or CXCR4 inhibitor (AMD3100, 100ng/mL), alone and in combination for 24h to study the effects on mast cell activation (chymase), PSC activation (collagen), nerve injury (AFT3) and markers of pain (substance P) by RT-PCR.
Results: (i) Compared to individual cultures, mast cells+PSC co-cultures showed significant upregulation of CXCR4 (p<0.05), while CXCL12 and chymase expression showed a trend to increase. Chymase expression was significantly suppressed (p<0.05) by the CXCL12 inhibitor alone and with AMD3100, compared to untreated cells.
(ii) In the mast cell, PSC, and neuron triple co-culture, chymase expression was significantly downregulated (p<0.05) by AMD3100 alone and in combination with CXCL12 inhibitor in comparison to cultures without treatment. ATF3 expression was also significantly decreased (p<0.05) by AMD3100.
Conclusion: In the presence of PSCs, mast cells were activated and DRGs exhibited signs of injury. These effects were inhibited by AMD3100.
Implication: PSC-mast cell-DRG interactions promote an inflammatory/neural injury milieu mediated by the CXCL12-CXCR4 axis, being a potential novel therapeutic target for alleviating pain in PC.