Treatment resistance after chemo-/immunotherapy occurs in patients with head and neck squamous cell cancers (HNSCs), including salivary gland cancers (SGCs). Interleukin-10 (IL-10), a cytokine with pro- and anti-cancer effects, has an unclear impact on HNSC/SGC cells. We show that HNSC patients exhibiting high expression of IL-10 and its receptor IL-10Rα experience have prolonged overall survival. Immunoreactive IL-10 was low in ductal cells of human SGC biopsies. Human (A253) and murine WR21-SGC cells expressed IL-10Rβ, but only A253 cells expressed IL-10 and IL-10Rα. The addition of recombinant IL-10 impaired SGC cell proliferation and induced apoptosis in vitro. N-acetylcysteine restored IL-10-induced reactive oxygen species (ROS) production but did not prevent IL-10-mediated viability loss. Mechanistically, recIL-10 delayed cell cycle progression from G0/G1 to the S phase with cyclin D downregulation and upregulation of NF-kB. IL-10 increased tumor necrosis factor-α (TNF-α) in A253 and WR21 and FasL in WR21 cells. Neutralizing antibodies against TNF-α and NF-kB inhibition restored SGC proliferation after IL-10 treatment, emphasizing the critical role of TNF-α and NF-kB in IL-10-mediated anti-tumor effects. These findings underscore the potential of IL-10 to impede SGC cell growth through apoptosis induction, unraveling potential therapeutic targets for intervention in salivary gland carcinomas.

Salivary gland cancers (SGCs) pose a therapeutic challenge due to their aggressive nature and limited treatment options. Ion transporters, particularly the sodium/iodide symporter (SLC5A5), which transport iodine in the form of iodide anion (I−) into cells, have emerged as potential therapeutic targets in tumors of glandular origin. Our research indicates that SLC5A5 is expressed predominantly in ductal cells of human and murine SGC cells. We assessed the effects of potassium iodide (KI), a source of iodide ions. KI treatment reduced SGC cell proliferation and viability without impacting migration. KI increased ROS levels and triggered caspase-dependent apoptosis, as indicated by the upregulation of the pro-apoptotic protein BAX, downregulation of the anti-apoptotic protein Bcl-2, and induction of SGC cell shrinkage. KI did not affect NF-κB or TNF-α and SLC5A5 expression. Adding the antioxidant N-acetylcysteine reversed KI-induced growth inhibition, underscoring ROS-induced oxidative stress’s crucial role in growth inhibition. While KI administered in drinking water to mice increased epidermal growth factor (EGF) expression in non-malignant salivary gland tissues, KI decreased EGF receptor (EGFR) expression in malignant SGC cell cultures, where EGFR signaling is frequently dysregulated in SGCs but promoted AKT phosphorylation. Combining KI and anti-EGFR treatment did not yield synergistic anti-SGC cell effects. The study underscores the therapeutic potential of KI as a standalone treatment in vitro for SGC cells. However, the upregulation of EGF in non-malignant tissues and, therefore, the possibility to enhance EGFR-driven signals and AKT phosphorylation after KI treatment in cancer patients could indicate a risk of rendering SGC cells more drug resistant, warranting further investigation to optimize its clinical application.