Evaluating the Regulatory Immunomodulation Effect of Irreversible Electroporation (IRE) in Pancreatic Adenocarcinoma

Background: Irreversible electroporation (IRE) has been demonstrated as an effective local method for locally advanced (stage 3) pancreatic adenocarcinoma. Immune regulatory T cells (Tregs) induce immunosuppression of tumors by inhibiting patients' anti-tumor adaptive immune response. This study aimed to evaluate the immunomodulation effect of IRE to identify an ideal time point for potential adjuvant immunotherapy.

Methods: This study prospectively evaluated an institutional review board-approved study of patients undergoing either in situ IRE or pancreatectomy. Patient blood samples were collected at different time points (before surgery [preOP] and on postoperative day [POD] 1, POD3, and POD5). Peripheral blood mononuclear cells (PBMCs) were isolated and evaluated for three different CD4 + Treg subsets (CD25 + CD4 +, CD4 + CD25 + FoxP3 +, CD4 + CD25 + FoxP3 -) by flow cytometry and analyzed for median fold change (MFC) between each two consecutive time points (MFC = log2(T2/T1)).

Results: The study analyzed 15 patients with in situ IRE (n = 11) or pancreatectomy (PAN) (n = 4). In both groups, CD25 + CD4 + Tregs decreased on POD1 followed by a steady increase in pancreatectomy, whereas the trend in the IRE group reversed between D3 and D5 (MFC: IRE [- 0.01], PAN [+ 0.39]). For each period, CD4 + CD25 + FoxP3 + Tregs showed the most dramatic inverse effect, with D3 to D5 showing the most change (MFC: IRE [- 0.18], PAN [+ 0.39]). Also, CD4 + CD25 + FoxP3 - Tregs showed an inverse effect between D3 and D5 (MFC: IRE [- 0.25], PAN [+ 0.49]). Altogether, the Treg trend was inversely affected by the in situ IRE procedure, with the greatest cumulative significant change for all three Treg subsets between D3 and D5 (MFC ± SEM: IRE [- 0.24 ± 0.05], PAN [+ 0.37 ± 0.02]; p = 0.016).

Conclusions: The study data suggest that in situ IRE procedure-mediated Treg attenuation between POD3 and POD5 can provide a clinical window of opportunity for potentiating clinical efficacy in combination with immunotherapy.