Background: Pancreatic cancer, a lethal malignancy is the fourth leading cause of cancer-related deaths in the United States. The standard chemotherapy with gemcitabine is ineffective in patients with metastatic tumors. Pancreatic cancer stem cells (CSCs) have been implicated in the development of pancreatic cancer metastasis, resistance to chemotherapy and its recurrence following surgical extirpation. We have shown that natural vitamin E δ-tocotrienol is the most bioactive tocotrienols against pancreatic cancer in vitro as well as in vivo models. The purpose of this study was to evaluate the chemosensitization of pancreatic tumor metastasis by δ-tocotrienol to gemcitabine in vitro as well as in vivo.
Methods: In vitro human metastatic pancreatic cancer cells L3.6pl and pancreatic cancer stem cells (PCSC) were treated with gemcitabine (5 μM) and δ-tocotrienol (50 μM) alone and in combination. Treated cells used for epithelial to mesenchymal transition (EMT), migration/invasion, microsphere/spheroid, and signaling markers assays. PCSC expressing luciferase was orthotopically implanted into pancreas of Athymic nude mice (n = 20) and after one week they were randomized into four groups: 1) vehicle control (ethanol extracted olive oil), 2) gemcitabine (100 mg/kg, IP, twice a week), 3) δ-tocotrienol (200 mg/kg, orally twice a day) and 4) gemcitabine + δ-tocotrienol. The treatment was continued for 4 weeks. The tumor volume, tumor weight, metastasis were recorded.
Results: Gemcitabine slightly inhibited the growth, migration/invasion of L3.6pl and PCSC in vitro and PCSC tumor growth (tumor volume and weight) in vivo. δ-tocotrienol significantly inhibited the growth, microsphere/spheroid, migration/invasion, EMT(E-cadherin to vimentin), angiogenesis (VEGF), PCSC transcription factors (Nanog, Oct4, and Sox2), tumor growth and liver/lung metastasis compared to control. The combination of both drugs synergistically inhibited the cancer and stem cell growth, EMT, migration/invasion, microsphere/spheroid, metastasis, angiogenesis, and PCSC transcription factors in vitro as well as in vivo.
Conclusion: Vitamin E δ-tocotrienol chemosensitizes human pancreatic tumor metastasis to gemcitabine through inhibition of EMT, migration, invasion, angiogenesis, cancer stem cell self-renewal, tumor growth and metastasis.
Citation Format: Kazim Husain, Said M. Sebti, Mokenge P. Malafa. Delta-tocotrienol chemosensitizes human pancreatic tumor metastasis to gemcitabine targeting cancer stem cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1098. doi:10.1158/1538-7445.AM2017-1098