ABSTRACT
Pancreatic cancer is one of the leading causes of cancerrelated mortality and has the lowest 5year survival rate. Therefore, novel strategies are urgently required to treat pancreatic cancer. Pancreatic ductal adenocarcinoma (PDAC) cells rely on enhanced lysosomal function for survival and proliferation to facilitate the degradation of contents accumulated via autophagy and macropinocytosis. Previously, we have reported that the combination of epidermal growth factor receptor/HER2 inhibitor lapatinib and sphingosine analog fingolimod (FTY720) confers a significant cytostatic effect in lung cancer cells. In the present study, the combined effects of these drugs on PDAC cell lines, BxPC3, KP4, PANC1 and MIA PaCa2, were examined. It was observed that FTY720 enhanced the lapatinibinduced cytotoxic effect and caused noncanonical and lysosomedependent death in PDAC cells. Lapatinib and FTY720 induced lysosomal swelling and inhibited lysosomal acidification. Combination treatment with lapatinib and FTY720 increased lysosomal membrane permeability, induced mitochondrial depolarization, induced endoplasmic reticulum stress and disturbed intracellular calcium homeostasis. Additionally, the cytotoxic effect of lapatinib was enhanced by hydroxychloroquine or the CDK4/6 inhibitor abemaciclib, both of which induce lysosomal dysfunction. Collectively, these results indicated that the lysosometargeted drug combination induces multiple organelle dysfunction and exerts a marked cytotoxic effect in PDAC cells.
Subject(s)
Carcinoma, Pancreatic Ductal/drug therapy , Fingolimod Hydrochloride/pharmacology , Lapatinib/pharmacology , Lysosomes/drug effects , Pancreatic Neoplasms/drug therapy , Aminopyridines/pharmacology , Antineoplastic Agents/pharmacology , Benzimidazoles/pharmacology , Cell Line, Tumor , Drug Synergism , Endoplasmic Reticulum Stress/drug effects , Humans , Hydroxychloroquine/pharmacology , Sphingosine 1 Phosphate Receptor Modulators/pharmacologyABSTRACT
Epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase and mutations in this gene are major drivers of lung cancer development. EGFR tyrosine kinase inhibitors (TKIs) are standard firstline therapies for patients with advanced nonsmall cell lung cancer (NSCLC) with activating EGFR mutations, but are not effective in patients with wildtype EGFR. In the present study, the cytotoxic effects of various TKIs against EGFR were investigated in wildtype NSCLC cells as single treatments or in combination with Fingolimod (FTY720), which has been approved for treating multiple sclerosis and has cytotoxic effects against several tumor cell lines. It was found that the combined treatment with TKIs lapatinib (Lap) or sorafenib (Sor) and FTY720 synergistically suppressed the viability of the NSCLC cell lines A549 and H596. Additionally, FTY720 inhibited lysosomal acidification and suppressed autophagy flux. Immunoblotting and reverse transcriptionquantitative polymerase chain reaction showed that FTY720 combined with Lap or Sor, enhanced endoplasmic reticulum (ER) stress loading and cell cycle arrest in A549 cells. The enhancement of ER stress loading and cell cycle arrest induced by combined treatment with Lap or Sor and FTY720, which was associated with the cytotoxicity induced by the combination of these drugs. These findings suggested that FTY720 improved TKI therapy in NSCLC patients with wildtype EGFR, by sensitizing NSCLC cells to TKIs.