δ-Tocotrienol, a natural form of vitamin E, inhibits pancreatic cancer stem-like cells and prevents pancreatic cancer metastasis

Abstract

The growth, metastasis, and chemotherapy resistance of pancreatic ductal adenocarcinoma (PDAC) is characterized by the activation and growth of tumor-initiating cells in distant organs that have stem-like properties. Thus, inhibiting growth of these cells may prevent PDAC growth and metastases. We have demonstrated that δ-tocotrienol, a natural form of vitamin E (VEDT), is bioactive against cancer, delays progression, and prevents metastases in transgenic mouse models of PDAC. In this report, we provide the first evidence that VEDT selectively inhibits PDAC stem-like cells. VEDT inhibited the viability, survival, self-renewal, and expression of Oct4 and Sox2 transcription factors in 3 models of PDAC stem-like cells. In addition, VEDT inhibited the migration, invasion, and several biomarkers of epithelial-to-mesenchymal transition and angiogenesis in PDAC cells and tumors. These processes are critical for tumor metastases. Furthermore, in the L3.6pl orthotopic model of PDAC metastases, VEDT significantly inhibited growth and metastases of these cells. Finally, in an orthotopic xenograft model of human PDAC stem-like cells, we showed that VEDT significantly retarded the growth and metastases of gemcitabine-resistant PDAC human stem-like cells. Because VEDT has been shown to be safe and to reach bioactive levels in humans, this work supports investigating VEDT for chemoprevention of PDAC metastases.

Vitamin E and cancer prevention: Studies with different forms of tocopherols and tocotrienols

“…δ‐T3 was shown to inhibit the formation of tumorspheres of human melanoma cells 147 . δ‐T3 was also reported to inhibit the expression of stem cell transcription factors, including NANOG, OCT4, and SOX2, in pancreatic cancer cells and surface stemness marker CD44 in xenograft tumors of pancreatic cancer cells 148 . γ‐T3 was reported to inhibit mevalonate pathway and activate de novo ceramide synthesis pathway, resulting in the reduced STAT‐3 mediated signaling and leading to the inhibition on breast cancer stem‐like cells 149 …”

“…δ‐T3 and γ‐T3 have been demonstrated to inhibit tumor growth in xenograft models of pancreatic cancer cells, 136,148 gastric cancer cells, 150 mouse mammary cancer cells, 151 liver cancer cells, 128 and melanoma cells, 147 as well as the transgenic pancreatic cancer mouse models (LSL‐KrasG12D; LSL‐Trp53R127H; and Pdx‐1‐Cre [KPC mice]) 152 …”

“…119 Using the same in vitro assays, δ-T3 was also found to suppress the migration and invasion of non-small lung cancer cells 124 and colon cancer cells. 154 Studies in xenograft models showed that δ-T3 inhibited pancreatic cancer tumor growth and liver and lung metastasis 148 and that tocotrienols-rich mixture inhibited lung metastasis of breast cancer cells. 151 Tocotrienols were also found to display antiangiogenesis activity in animal models.…”

“…151 Tocotrienols were also found to display antiangiogenesis activity in animal models. For example, δ-T3 and γ-T3 suppressed the tumor angiogenesis of xenograft tumors of pancreatic cancer cells, 148 colorectal cells, 155 and liver cancer cells 128 as well as pancreatic tumors developed in KPC transgenic mice. 152 The antiangiogenesis effect of tocotrienols has been well demonstrated in typical angiogenesis tests such as tube formation assay of HUVEC 128 and chick chorioallantoic membrane assays.…”

“…δ-T3 was also reported to inhibit the expression of stem cell transcription factors, including NANOG, OCT4, and SOX2, in pancreatic cancer cells and surface stemness marker CD44 in xenograft tumors of pancreatic cancer cells 148. γ-T3 was T A B L E 4 Laboratory studies on tocotrienols and cancer Experimental model Treatment Conclusion Reference Human colon cancer cells SW620 4-20 δ-T3 Downregulated WNT pathway (↓CTNNB1, ↓WNT1, and ↓CCND1) Zhang et al 116 Human colon cancer cells HT-29 45 and 60 μM γ-T3 Inhibited β-Catenin/Tcf signaling (↓CTNNB1, ↓BIRC5, ↓CCND1, and ↓c-MYC↓) Xu et al 117 Human colon cancer cells SW620 and HCT-Induced parapoptosis-like cell death by inhibiting Wnt signaling pathway (↓c-JUN, ↓CTNNB1, and ↓CCND1) Zhang et al 118 Human breast cancer cells MDA-MB-231 and T-47D 2-6 μM γ-T3 Inhibits EMT and proliferation by ↓canonical Wnt/β-catenin signaling pathway Ahmed et al 119 Human colon cancer cells SW620 cells; xenograft tumors 5, 10, and 20 mg/kg bw TRF Inhibited tumor growth by ↑WNT pathway Zhang et al 120 Human oral cancer cells B88 50 μM γ-T3 Improved chemosensitivity to docetaxel by ↓BIRC5, ↓c-IAP-1, ↓cIAP-2, ↓XIAP, ↓BCL2, and downregulating the expression of NF-kB-mediated antiapoptotic gene products Kani et al 121 Murine RAW 264.7 macrophages; A20 −/− and A20 +/+ mouse embryonic fibroblasts 10 and 20 μM δ-T3 Inhibited activation of NF-κB and TAK1, ↓IL-6, ↑A20, ↑CYLD, induced cellular stress, and ↑intracellular dihydroceramides Yang and Jiang 122Human lung cancer cells A549 andH1299 10-40 μM δ-T3 Inhibited proliferation, cell invasion, cell aggregation, and adhesion, ↓MMP-9, ↑miR-451, inhibited uPa/NOTCH1 pathway proteins, and inhibited NF-κB DNA-binding activity Rajasinghe et al 123 Human lung cancer cells A549 and H1650 15 μM δ-T3 Augmented cisplatin-induced inhibition of cell invasion via the suppression of Notch-1 signaling pathway (↓NOTCH1, ↓HES1, ↓pro-CASP-3, ↓PARP, ↓VEGF, and ↓MMP9) Ji et al 124 Human lung cancer cells A549 and H1299 20-30 μM δ-T3 Arrested G0/G1 cell cycle and inhibited cell invasion and migration by ↑miR-34a; ↓NOTCH1, HES1, PARP, Bcl-xL, BIRC5, NF-κB, VEGF, and MMP9 Ji et al 125 Human non-small cell lung cancer cell line A549 and H1299 10, 20, and 30 µM δ-T3 Dose-and time-dependent inhibition of cell growth, cell migration, tumor cell invasiveness, and induction of apoptosis associated with decreases in NOTCH1, HES1, survivin, MMP9, VEGF, and VCL-XL expression Ji et al 126 Human lung cancer A549 and H1299 cells 10, 20, 30 μM δ-T3 Inhibited glutamine transporters and mTOR pathway Rajasinghe et al 127 HUVEC; human liver cancer cells HCCLM3; xenograft tumor 50 μM γ-T3; 3.25 mg γ-T3 daily, 5 d a wk Inhibited VEGF-induced potential of migration and invasion of HUVEC by downregulating AKT/mTOR signaling pathway; inhibited tumor growth and VEGF-induced angiogenesis Siveen et al 128 Human bladder cancer cells T24, 5637, J82, and UMUC-3 50, 100, and 150 μM δ-T3 Inhibited growth, induced G1 arrest and apoptosis by ↑CDKN1A, ↑CDKN1B, ↓pro-CASP-3, ↑c-CASP-3, ↑BAX, and ↓BCL2 Ye et al 129 Human prostate cancer cells PC3 24 and 48 μM δ-T3 Induced cytotoxicity by ↓SRC, ↓p-SRC, ↓STAT3, and ↓p-STAT3 Sugahara et al 130 Human prostate cancer cells PC3; xenograft tumor 12 μM γ-T3 Polysaccharopeptides enhanced the effect of γ-T3 in inhibiting cell colony formation by ↑p-AMPK and inhibiting tumor growth Liu et al 131 Human breast cancer cells T47D 5 μM γ-T3 Inhibited exosomes-dependent (ED) cell growth; ↓ED HER3, and HER4 levels; ↓HER3/HER4 heterodimer downstream signaling; disrupted the integrity of lipid raft microdomain; ↓heregulin and mitogenic biopotency Alawin et al 132 Human breast cancer cells SKBR3 and BT474 4 μM γ-T3 The anticancer effect of γ-T3 is associated with its accumulation in the lipid raft microdomain due to ↓HER2 dimerization and ↓p-HER2 Induced apoptosis via ↑EGR-1/BAX Wang et al 134 Human breast cancer cells MDA-MB-231 and MDA-MB-468 30-100 μM δ-T3 Inhibited proliferation and induced apop...…”