CpG therapeutic efficacy in a murine model of metastatic Lymphangioleiomyomatosis (LAM) is mediated by plasmacytoid dendritic cell and T cell immune responses

LAM is a slow growing, metastasizing neoplasm affecting women of reproductive age, marked by abnormal growth of smooth muscle-like cells leading to cystic lung destruction. LAM has hallmarks of cancer, like expression of immune checkpoint receptors. Effective cancer therapies promote robust T cell responses through activated dendritic cells (DCs). Anti-cancer strategies, like toll like receptor (TLR) activation and immune checkpoint inhibition could work as LAM therapy. In this study, we examine the effect of CpG, a TLR9 agonist, on the DC and T cell responses in murine LAM. We used a mouse model of metastatic LAM to determine survival after biweekly intranasal CpG therapy (10μg/ 5μg) with/ without systemic α-PD-1, rapamycin, or α-CD317 therapy. We used ELISA to measure the cytokine profile and flow cytometry to quantify cell populations between CpG-treated and untreated LAM lungs. We found that CpG treatment enhances median survival from 32 to 60 days in murine LAM (p <0.0001). Efficacy of CpG treatment in LAM is facilitated by plasmacytoid DCs. pDC depletion in CpG-treated mice decreases survival from 60 to 52 days (p=0.028). CpG-treated LAM lungs also produce more IFN-α (p=0.031). CpG-treated LAM lungs have increased IFN-γ (p= 0.012) and IL-12 (p= 0.005), cytokines secreted by cytotoxic T cells. CpG-treatment is synergistic with α-PD-1 checkpoint inhibition (p=0.004) and can be administered with rapamycin without adverse effects on median survival. In LAM, CpG therapy is mediated by pDC dependent immune responses and cytotoxic T cells. This suggests that adjuvant immunotherapy, like CpG, may offer new treatment options for LAM compatible with the current standard of care, rapamycin. The LAM Foundation Research Grant Award