Alterations in Cellular Cholesterol Content Can Be a Potential Anticancer Strategy Volume 1 - Issue 3

Jui Ling Hsu and Jih Hwa Guh*

• School of Pharmacy, National Taiwan University, Taiwan

Received: August 29, 2017;   Published: August 31, 2017

Corresponding author: Jih Hwa Guh, School of Pharmacy, National Taiwan University, No. 33, Linsen S. Rd., Taipei 100, Taiwan

DOI: 10.26717/BJSTR.2017.01.000319

Cholesterol, a unique lipid molecule biosynthesized by all animal cells, is an essential structural constituent in cell membranes to maintain their structural integrity and fluidity. Cholesterol is critical to synthesis of hormones, vitamin D and bile acid, multiple cellular signaling, intracellular transport and a variety of cell functions [1,2]. Cholesterol is necessary to the structure and function of caveolae and clathrin-coated pits, enabling the endocytotic activity [3,4]. In recent decades, increasing lines of evidence show that lipid rafts, which are membrane micro domains assemble glycosphingolipids, protein receptors and kinases, preferentially associate with cholesterol and saturated lipids in driving a wide variety of cellular signaling pathways [5,6]. Not only in normal cellular and physiological functions, intracellular cholesterol homoeostasis once deregulated can be responsible for the development of malignancies through decreasing chemotherapeutic susceptibility and increasing resistance in cancer cells, inhibiting the release of mitochondrial cell death-promoting molecules, activating survival kinases and many other mechanisms [7-9]. Epidemiological studies also have suggested a positive correlation between serum cholesterol levels and cancer risk [9-11]. These studies support the notion that the development of cholesterol-lowering agents can be a potential anticancer strategy.

Abbreviations: PL3K: Phosphatidylinositol 3 Kinase; mTOR: mammalian Target of Rapamycin; SREBP: Sterol Regulatory Element Binding Protein

Phosphatidylinositol 3 kinase (PI3K), protein kinase B (Akt) and mammalian target of rapamycin (mTOR) are three serine/ threonine-specific protein kinases that coordinately regulate cell cycle, quiescence, transformation, proliferation and survival [12]. Accumulating lines of evidence suggest that cholesterol homeostasis and biosynthesis usually appear to be altered in cancer cells and, once inhibited, the tumor genesis can be blocked indicating that cholesterol content tightly regulates cancer cell fate [13,14]. Recent studies have reported that constitutive activation of PI3K/Akt signaling pathway induces an increase in intracellular cholesterol content in cancer cells through multiple mechanisms, including induction of LDL receptor-related cholesterol import, activation of sterol regulatory element binding protein (SREBP)- dependent cholesterol synthesis and inhibition of ATP-binding cassette transporter ABCA1-regulated mTORC1-dependent cholesterol export [8,15-17]. Further studies reveal that the increase of cholesterol levels is responsible to cancer cell growth, cell survival and cancer aggressiveness and bone metastases [15, 16,18-21]. The mechanism that PI3K/Akt/mTOR pathway regulates intracellular cholesterol levels has been identified, suggesting Niemann-Pick disease type C1 (NPC1) protein serves as a crucial target. NPC1 is a membrane protein which controls intracellular cholesterol trafficking in mammals [22]. Cholesterol binds to NPC1 with hydroxyl group in the binding pocket, leading to the export from the limiting membrane of late endosomes/ lysosomes to the endoplasmic reticulum and plasma membrane [23]. Recently, the link between NPC1 degradation and Akt/mTOR pathway has been addressed in several types of cancer [24-26]. It has been demonstrated that inhibition of Akt/mTOR pathway induces a decrease in NPC1 ubiquitination, suggesting a role of Akt/ mTOR pathway in NPC1 proteasomal degradation. These studies reveal Akt serving as a key regulator on NPC1 degradation and connect this protein with cancer cell proliferation and migration [24,25]. Moreover, Naren and the colleagues have used U18666A, an inhibitor of NPC1 function, to inhibit cholesterol trafficking to mimic the condition of NPC1 defect in cells, leading to higher NPC1 expression and higher resistance against imatinib mesylate, a chemotherapy medication used to treat chronic myelogenous leukemia [27]. The study suggests that cells with highly expressed NPC1 may have higher resistance to cancer chemotherapeutic agents.

Cholesterol also can be an upstream effectors to regulate PI3K/ Akt activities. Several studies have reported that the depletion of cholesterol from plasma membranes with beta-cyclodextrins is able to disrupt PI3K/Akt signal transduction [28-30]. The studies also reveal the importance of lipid raft integrity. Lipid rafts are dynamic plasma membrane micro domains which have been implicated in cell survival, proliferation, cell adhesion and invasion and cholesterol metabolism. Lipid rafts can form unique domains with diverse compositions and assist signal transduction through recruiting target proteins in response to intracellular and extracellular stimuli [31-33]. A wide variety of proteins related to cancer development are associated with lipid rafts, including growth factor receptors, serine/threonine protein kinases (PI3K/Akt/mTOR) and integrins [34-36]. Despite lipid rafts are hubs of many critical survival proteins, recent studies have provided evidence suggesting that lipid rafts can also orchestrate death receptor-mediated extrinsic apoptotic signaling [37-39]. The synthetic alkyllysophospholipid edelfosine and derivatives have a high affinity for cholesterol and are trapped in lipid rafts in a number of solid tumors and malignant hematological cells, inducing translocation of death receptors and downstream signaling molecules to these membrane micro domains and eventually leading to apoptosis of cancer cells [39- 43]. Edelfosine also can displace PI3K/Akt signal transduction from lipid rafts, inducing PI3K/Akt inhibition. Therefore, lipid rafts can serve as hubs where separation between pro-apoptotic and prosurvival cellular targets can take place [34].

It has been suggested that cancer cells have higher levels of cholesterol-rich lipid rafts compared to those in normal cells. Li and the colleagues have studied and compared the raft levels and effect of methyl-beta cyclodextrin-mediated raft disruption on cell viability of human cancer cell lines versus their normal counterparts. The cholesterol depletion caused apoptosis in human epidermoid carcinoma A431 cells involving decreased raft levels, Akt inactivation, and Bcl-xL down-regulation and caspase-3 activation regardless of epidermal growth factor receptor activation. The Akt activation and cell viability can be rescued by cholesterol replenishment [44]. Notably, they have reported that both breast and prostate cancer cell lines have more lipid rafts which lead to their higher susceptibility to apoptotic stimuli caused by cholesterol depletion [44]. These studies also suggest a potential use of lipid raft-modulating agents in cancer cells those have increased levels of lipid rafts.

Recent studies have addressed the alterations of specific lipid molecules found in cancer cells as well as in tumor microenvironment [45-47]. Moreover, lipid rafts are considered as a center to couple between membrane microenvironment and drug resistance since membrane lipid composition is tightly relevant to the function of ATP-binding cassette transporter P-glycoprotein (Pgp). It has been evident that the Pgp activity is highly sensitive to the presence of cholesterol. However, the membrane fluidity does not solely explain cholesterol-dependent alterations of Pgp-activity. In contrast, accurate lipid raft properties may predominantly be responsible to the Pgp-transport capacity [48,49]. These studies also support the notion that cholesterol depletion may sensitize chemotherapeutic agents in killing cancer cells through the inhibition of drug resistance. It has been supported by the observations that melittin, a Chinese traditional medicine, sensitizes gemcitabineinduced apoptosis in pancreatic ductal adenocarcinoma cells by down-regulating cholesterol pathway and decreasing drug resistance [50]. Similar study has demonstrated that a ginsenoside derivative, which appears to redistribute lipid rafts and Pgp, results in an accumulation of doxorubicin by decreasing Pgp activity in doxorubicin-resistant cells, leading to chemotherapeutic amplification [51]. These studies suggest that lipid raft-modulating agents may have potential in reducing multidrug resistance activity for chemotherapeutic sensitization.

Because of the crucial roles played by cholesterol in cancer development, the interruption of cholesterol supplementation and/ or lipid raft integrity can be a potential strategy in the development of cancer chemotherapeutic agents. Statins, well known competitive inhibitors of hydroxymethylglutaryl-CoA reductase enzyme (HMGCoA reductase), are widely used as cholesterol-lowering agents. In recent decades, much attention has been directed toward the use of statins in oncological therapy. Accumulated cellular and animal studies show an adequate anticancer effect of statins including inhibition of cell proliferation and invasion, and induction of apoptosis and differentiation. Among the statin family, lovastatin, simvastatin, atorvastatin, cerivastatin and fluvastatin have been extensively elucidated and the signaling pathways have been reported regarding the inhibition of PI3K/Akt/mTOR/p70S6K pathway, deregulating cell cycle proteins, blocking MAPK/Erk signaling, activation of JNK pathway, inhibition of RhoA membrane translocation from cytosol, F-actin depolymerization and inhibition of actin stress fiber assembly [52-61]. Statins may also induce a decrease of cholesterol content in lipid raft, suppress caveolin-1 expression in lipid rafts, and induce Fas translocation into lipid rafts, suggesting that statins may trigger apoptotic cell death through the modulation of death receptors in lipid rafts [62]. Furthermore, statins have been studied to inhibit angiogenesis through downregulation of VEGF, inhibition of endothelial cell proliferation and block of adhesion to extracellular matrix. However, it has been noted that different statin may exert dual and concentration-dependent impact on regulating angiogenic activities of human primary macrovascular endothelial cells [52,63]. Altogether, statins can induce different effects depending on the concentration, duration of exposure of cells to statins, cell lines and the type of statin being used [64].

In cancer patients, the efficacy of statins as chemotherapeutic drugs has been evaluated both in monotherapy and in combinatory therapy with clinical chemotherapeutic drugs [52]. Some clinical studies have demonstrated a positive outcome. Kawata and the colleagues have evaluated the efficacy of pravastatin combined with 5-Fu in patients with unrespectable hepatocellular carcinoma. Results show a significant prolonged survival in statin-treated group [65]. Similar positive effects have been demonstrated in the report by Graf and the colleagues on the treatment of patients with hepatocellular carcinoma by transarterial chemoembolization combined with pravastatin [66]. Several epidemiologic studies also suggest a positive correlation between increased serum cholesterol content and risk for some cancer types including prostate cancer, melanoma and non-metastatic rectal cancer [15,52,67-69]. On the contrary, some studies show that statins have failed to improve the median survival of patients with certain types of cancer. The meta-analysis of large randomized clinical trials also suggests no association between cholesterol and cancer [15,52,70,71]. Because of the controversy, additional studies are required to connect the mechanism evidence, clinical studies and epidemiological data to solve these problems.

Omega-3 polyunsaturated fatty acids, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), control some key cellular mechanisms and play a beneficial role in inflammatory diseases. However, the evidence connecting the consumption of omega-3 polyunsaturated fatty acids to a lower cancer risk is insufficient [72] exception possibly of breast cancer [73]. Several studies have reported that EPA and DHA can inhibit cell proliferation and induce apoptosis of MDA-MB-231 human breast cancer cells through the incorporation of these fatty acids into lipid rafts, leading to an activation of p38MAPK and a decrease in EGFR levels in lipid rafts in spite of the accompanied phosphorylation of EGFR [74]. Moreover, both EPA and DHA can reduce surface expression of CXCR4, leading to a decrease of CXCR4-mediated cell migration of MDA-MB-231 cells [75]. These studies have provided evidence that omega-3 polyunsaturated fatty acids can modify lipid raft in both biochemical and biophysical features, decreasing the content of cholesterol and distribution of key proteins [76]. These effects can ultimately induce a decrease of cell proliferation and metastasis, and an increase of apoptosis in breast cancer cells.

From a large body of evidence, lipid raft modifying/cholesterol lowering agents can decrease lipid raft associated pro-survival protein (e.g., growth factor receptors and PI3K, Akt and mTOR kinases) and in induce translocation of death receptors. These impacts can eventually lead to the inhibition of cell proliferation and metastasis, and induction of cell death. However, the solubility, pharmacokinetics and delivery of the high lipophilic agents are key issues to solve. Therefore, several statin-loaded nanoparticles have been developed such as solutol-based lipid nanocapsules and cholic acid core, star-shaped polymer consisting of poly (D,L-lactideco- glycolide) nanoparticles are able to display good anticancer activities in breast cancer [77,78]. It has been, therefore, suggested that the development of lipid raft modifying/cholesterol lowering agents is a potential anticancer strategy if the solubility and drug delivery can be appropriately solved.

1. Zerbinati C, Iuliano L (2017) Cholesterol and related sterols autoxidation. Free Radic Biol Med 111: 151-155.
2. Incardona JP, Eaton S (2000) Cholesterol in signal transduction. Curr Opin Cell Biol 12(2): 193-203.
3. Moerke C, Mueller P, Nebe B (2016) Attempted caveolae-mediated phagocytosis of surface-fixed micro-pillars by human osteoblasts. Biomaterials. 76: 102-114.
4. Navarro G, Borroto-Escuela DO, Fuxe K, Franco R, Navarro G, et al. (2014) Potential of caveolae in the therapy of cardiovascular and neurological diseases. Front Physiol 5: 370.
5. Sezgin E, Levental I, Mayor S, Eggeling C (2017) The mystery of membrane organization: composition, regulation and roles of lipid rafts. Nat Rev Mol Cell Biol 18(6): 361-374.
6. Gajate C, Mollinedo F (2015) Lipid raft-mediated Fas/CD95 apoptotic signaling in leukemic cells and normal leukocytes and therapeutic implications. J Leukoc Biol 98(5): 739-759.
7. Montero J, Morales A, Llacuna L, Lluis JM, Terrones O, et al. (2008) Mitochondrial cholesterol contributes to chemotherapy resistance in hepatocellularcarcinoma. Cancer Res 68(13): 5246-5256.
8. Smith B, Land H (2012) Anticancer activity of the cholesterol exporter ABCA1 gene. Cell Rep 2(3): 580-590.
9. Kuzu OF, Gowda R, Noory MA, Robertson GP (2017) Modulating cancer cell survival by targeting intracellular cholesterol transport. Br J Cancer 117(4): 513-524.
10. Platz EA, Clinton SK, Giovannucci E (2008) Association between plasma cholesterol and prostate cancer in the PSA era. Int J Cancer 123(7): 1693-1698.
11. Nielsen SF, Nordestgaard BG, Bojesen SE (2012) Statin use and reduced cancer-related mortality. N Engl J Med 367(19): 1792-1802.
12. Hermida MA, Dinesh Kumar J, Leslie NR (2017) GSK3 and its interactions with the PI3K/AKT/mTOR signaling network. Adv Biol Regul 65: 5-15.
13. Flavin R, Zadra G, Loda M (2011) Metabolic alterations and targeted therapies in prostate cancer. J Pathol. 223(2): 283-294.
14. Casey SC, Amedei A, Aquilano K, Azmi AS, Benencia F, et al. (2015) Cancer prevention and therapy through the modulation of the tumor microenvironment. Semin Cancer Biol 35 Suppl: S199-223.
15. Kuzu OF, Noory MA, Robertson GP (2016) The Role of Cholesterol in Cancer. Cancer Res 76(8): 2063-2070.
16. Porstmann T, Santos CR, Griffiths B, Cully M, Wu M, et al. (2008) SREBP activity is regulated by mTORC1 and contributes to Akt-dependent cell growth. Cell Metab 8(3): 224-236.
17. Dong F, Mo Z, Eid W, Courtney KC, Zha X (2014) Akt inhibition promotes ABCA1-mediated cholesterol efflux to ApoA-I through suppressing mTORC1. PLoS One 9(11): e113789.
18. Griffiths B, Lewis CA, Bensaad K, Ros S, Zhang Q, et al. (2013) Sterol regulatory element binding protein-dependent regulation of lipid synthesis supports cell survival and tumor growth. Cancer Metab 1(1): 3.
19. Yue S, Li J, Lee SY, Lee HJ, Shao T, et al. (2014) Cholesteryl ester accumulation induced by PTEN loss and PI3K/AKT activation underlies human prostate cancer aggressiveness. Cell Metab 19(3): 393-406.
20. Guo D, Reinitz F, Youssef M, Hong C, Nathanson D, et al. (2011) An LXR agonist promotes glioblastoma cell death through inhibition of an EGFR/ AKT/SREBP-1/LDLR-dependent pathway. Cancer Discov 1(5): 442-456.
21. Thysell E, Surowiec I, Hörnberg E, Crnalic S, Widmark A, et al. (2010) Metabolomic characterization of human prostate cancer bone metastases reveals increased levels of cholesterol. PLoS One 5(12): e14175.
22. Wang MD, Kiss RS, Franklin V, McBride HM, Whitman SC, et al. (2007) Different cellular traffic of LDL-cholesterol and acetylated LDLcholesterol leads to distinct reverse cholesterol transport pathways. J Lipid Res 48(3): 633-645.
23. Pfeffer SR (2016) Clues to NPC1-mediated cholesterol export from lysosomes. Proc Natl Acad Sci USA 113(29): 7941-7943.
24. Du X, Zhang Y, Jo SR, Liu X, Qi Y, et al. (2015) Akt activation increases cellular cholesterol by promoting the proteasomal degradation of Niemann-Pick C1. Biochem J 471(2): 243-253.
25. Gowda R, Inamdar GS, Kuzu O, Dinavahi SS, Krzeminski J, et al. (2017) Identifying the structure-activity relationship of leelamine necessary for inhibiting intracellular cholesterol transport. Oncotarget 8(17): 28260- 28277.
26. Head SA, Shi WQ, Yang EJ, Nacev BA, Hong SY, et al. (2017) Simultaneous Targeting of NPC1 and VDAC1 by Itraconazole Leads to Synergistic Inhibition of mTOR Signaling and Angiogenesis. ACS Chem Biol 12(1): 174-182.
27. Naren D, Wu J, Gong Y, Yan T, Wang K, et al. (2016) Niemann-Pick disease type C1(NPC1) is involved in resistance against imatinib in the imatinibresistant Ph+ acute lymphoblastic leukemia cell line SUP-B15/RI. Leuk Res 42: 59-67.
28. Yamaguchi R, Perkins G, Hirota K (2015) Targeting cholesterol with β-cyclodextrin sensitizes cancer cells for apoptosis. FEBS Lett 589(24 Pt B): 4097-4105.
29. Motoyama K, Kameyama K, Onodera R, Araki N, Hirayama F, et al. (2009) Involvement of PI3K-Akt-Bad pathway in apoptosis induced by 2,6-di- O-methyl-beta-cyclodextrin, not 2,6-di-O-methyl-alpha-cyclodextrin, through cholesterol depletion from lipid rafts on plasma membranes in cells. Eur J Pharm Sci 38(3): 249-2461.
30. Huang FC (2014) The critical role of membrane cholesterol in salmonella-induced autophagy in intestinal epithelial cells. Int J Mol Sci 15(7): 12558-12572.
31. Varshney P, Yadav V, Saini N (2016) Lipid rafts in immune signalling: current progress and future perspective. Immunology. 149(1): 13-24.
32. Gajate C, Mollinedo F (2015) Lipid raft-mediated Fas/CD95 apoptotic signaling in leukemic cells and normal leukocytes and therapeutic implications. J Leukoc Biol 98(5): 739-759.
33. Martinez-Outschoorn UE, Sotgia F, Lisanti (2015) Caveolae and signalling in cancer. Nat Rev Cancer 15(4): 225-237.
34. Mollinedo F, Gajate C (2015) Lipid rafts as major platforms for signaling regulation in cancer. Adv Biol Regul 57: 130-146.
35. Crane JM, Tamm LK (2004) Role of cholesterol in the formation and nature of lipid rafts in planar and spherical model membranes. Biophys J 86(5): 2965-2979.
36. Deb M, Sengupta D, Patra SK (2012) Integrin-epigenetics: a system with imperative impact on cancer. Cancer Metastasis Rev 31(1-2): 221-234.
37. Gajate C, Mollinedo F (2017) Isolation of Lipid Rafts Through Discontinuous Sucrose Gradient Centrifugation and Fas/CD95 Death Receptor Localization in Raft Fractions. Methods Mol Biol 1557: 125- 138.
38. Chen YC, Kung FL, Tsai IL, Chou TH, Chen IS, et al. (2010) Cryptocaryone, a natural dihydrochalcone, induces apoptosis in human androgen independent prostate cancer cells by death receptor clustering in lipid raft and nonraft compartments. J Urol 183(6): 2409-2418.
39. Jaffrès PA, Gajate C, Bouchet AM, Couthon-Gourvès H, Chantôme A, et al. (2016) Alkyl ether lipids, ion channels and lipid raft reorganization in cancer therapy. Pharmacol Ther 165: 114-131.
40. Lim SC, Parajuli KR, Han SI (2016) The alkyllysophospholipid edelfosine enhances TRAIL-mediated apoptosis in gastric cancer cells through death receptor 5 and the mitochondrial pathway. Tumour Biol 37(5): 6205-6216.
41. Gajate C, Mollinedo F (2015) Lipid raft-mediated Fas/CD95 apoptotic signaling in leukemic cells and normal leukocytes and therapeutic implications. J Leukoc Biol 98(5): 739-759.
42. Gajate C, Mollinedo F (2014) Lipid rafts, endoplasmic reticulum and mitochondria in the antitumor action of the alkylphospholipid analog edelfosine. Anticancer Agents Med Chem 14(4): 509-527.
43. Gajate C, Mollinedo F (2011) Lipid rafts and Fas/CD95 signaling in cancer chemotherapy. Recent Pat Anticancer Drug Discov 6(3): 274-283.
44. Li YC, Park MJ, Ye SK, Kim CW, Kim YN (2006) Elevated levels of cholesterol-rich lipid rafts in cancer cells are correlated with apoptosis sensitivity induced by cholesterol-depleting agents. Am J Pathol 168(4): 1107-1118.
45. Zhang Q, Wakelam MJ (2014) Lipidomics in the analysis of malignancy. Adv Biol Regul 54: 93-98.
46. Matos Do Canto L, Marian C, Varghese RS, Ahn J, Da Cunha PA, et al. (2016) Metabolomic profiling of breast tumors using ductal fluid. Int J Oncol 49(6): 2245-2254.
47. Knopf JD, Tholen S, Koczorowska MM, De Wever O, Biniossek ML, et al. (2015) The stromal cell-surface protease fibroblast activation protein-α localizes to lipid rafts and is recruited to invadopodia. Biochim Biophys Acta 1853(10 Pt A): 2515-2525.
48. Meyer dos Santos S, Weber CC, Franke C, Müller WE, Eckert GP (2007) Cholesterol: Coupling between membrane microenvironment and ABC transporter activity. Biochem Biophys Res Commun 354(1): 216-221.
49. Fenyvesi F, Fenyvesi E, Szente L, Goda K, Bacsó Z, et al. (2008) P-glycoprotein inhibition by membrane cholesterol modulation. Eur J Pharm Sci 34(4-5): 236-242.
50. Wang X, Xie J, Lu X, Li H, Wen C, et al. (2017) Melittin inhibits tumor growth and decreases resistance to gemcitabine by down regulating cholesterol pathway gene CLU in pancreatic ductal adenocarcinoma. Cancer Lett 399: 1-9.
51. Yun UJ, Lee JH, Koo KH, Ye SK, Kim SY, et al. (2013) Lipid raft modulation by Rp1 reverses multidrug resistance via inactivating MDR-1 and Src inhibition. Biochem Pharmacol 85(10): 1441-1453.
52. Gazzerro P, Proto MC, Gangemi G, Malfitano AM, Ciaglia E, et al. (2012) Pharmacological actions of statins: a critical appraisal in the management of cancer. Pharmacol Rev 64(1): 102-146.
53. Vallianou NG, Kostantinou A, Kougias M, Kazazis C (2014) Statins and cancer. Anticancer Agents Med Chem 14(5): 706-712.
54. Zhuang L, Kim J, Adam RM, Solomon KR, Freeman MR (2005) Cholesterol targeting alters lipid raft composition and cell survival in prostate cancer cells and xenografts. J Clin Invest 115(4): 959-968.
55. Wang T, Seah S, Loh X, Chan CW, Hartman M, et al. (2016) Simvastatininduced breast cancer cell death and deactivation of PI3K/Akt and MAPK/ERK signalling are reversed by metabolic products of the mevalonate pathway. Oncotarget 7(3): 2532-2544.
56. Rao S, Lowe M, Herliczek TW, Keyomarsi K (1998) Lovastatin mediated G1 arrest in normal and tumor breast cells is through inhibition of CDK2 activity and redistribution of p21 and p27, independent of p53. Oncogene 17(18): 2393-2402.
57. Denoyelle C, Albanese P, Uzan G, Hong L, Vannier JP, et al. (2003) Molecular mechanism of the anti-cancer activity of cerivastatin, an inhibitor of HMG-CoA reductase, on aggressive human breast cancer cells. Cell Signal 15(3): 327-338.
58. Koyuturk M, Ersoz M, Altiok N (2007) Simvastatin induces apoptosis in human breast cancer cells: p53 and estrogen receptor independent pathway requiring signaling through JNK. Cancer Lett 250(2): 220-228.
59. Sassano A, Katsoulidis E, Antico G, Altman JK, Redig AJ, et al. (2007) Suppressive effects of statins on acute promyelocytic leukemia cells. Cancer Res 67(9): 4524-4532.
60. Collisson EA, Kleer C, Wu M, De A, Gambhir SS, et al. (2003) Atorvastatin prevents RhoC isoprenylation, invasion, and metastasis in human melanomacells. Mol Cancer Ther 2(10): 941-948.
61. Kusama T, Mukai M, Iwasaki T, Tatsuta M, Matsumoto Y, et al. (2001) Inhibition of epidermal growth factor-induced RhoA translocation and invasion of human pancreatic cancer cells by 3-hydroxy-3- methylglutaryl-coenzyme a reductase inhibitors. Cancer Res 61(12): 4885-4891.
62. Wu H, Jiang H, Lu D, Xiong Y, Qu C, et al. (2009) Effect of simvastatin on glioma cell proliferation, migration, and apoptosis. Neurosurgery 65(6): 1087-1096.
63. Frick M, Dulak J, Cisowski J, Józkowicz A, Zwick R, et al. (2003) Statins differentially regulate vascular endothelial growth factor synthesis in endothelial and vascular smooth muscle cells. Atherosclerosis 170(2): 229-236.
64. Matusewicz L, Meissner J, Toporkiewicz M, Sikorski AF (2015) The effect of statins on cancer cells--review. Tumour Biol 36(7): 4889-4904.
65. Kawata S, Yamasaki E, Nagase T, Inui Y, Ito N, et al. (2001) Effect of pravastatin on survival in patients with advanced hepatocellular carcinoma. A randomized controlled trial. Br J Cancer 84(7): 886-891.
66. Graf H, Jüngst C, Straub G, Dogan S, Hoffmann RT, et al. (2008) Chemoembolization combined with pravastatin improves survival in patients withhepatocellular carcinoma. Digestion 78(1): 34-38.
67. Shafique K, McLoone P, Qureshi K, Leung H, Hart C, et al. (2012) Cholesterol and the risk of grade-specific prostate cancer incidence: evidence from two largeprospective cohort studies with up to 37 years’ follow up. BMC Cancer 12: 25.
68. Pelton K, Freeman MR, Solomon KR (2012) Cholesterol and prostate cancer. Curr Opin Pharmacol 12(6): 751-759.
69. Katz MS, Minsky BD, Saltz LB, Riedel E, Chessin DB, et al. (2005) Association of statin use with a pathologic complete response to neoadjuvant chemoradiation for rectal cancer. Int J Radiat Oncol Biol Phys 62(5): 1363-1370.
70. Bjerre LM, LeLorier J (2001) Do statins cause cancer? A meta-analysis of large randomized clinical trials. Am J Med 110(9): 716-723.
71. Nielsen SF, Nordestgaard BG, Bojesen SE (2012) Statin use and reduced cancer-related mortality. N Engl J Med 367(19): 1792-1802.
72. Sala-Vila A, Calder PC (2011) Update on the relationship of fish intake with prostate, breast, and colorectal cancers. Crit Rev Food Sci Nutr 51(9): 855-871.
73. Zheng JS, Hu XJ, Zhao YM, Yang J, Li D (2013) Intake of fish and marine n-3 polyunsaturated fatty acids and risk of breast cancer: meta-analysis of data from 21 independent prospective cohort studies. BMJ 346: f3706.
74. Schley PD, Brindley DN, Field CJ (2007) (n-3) PUFA alter raft lipid composition and decrease epidermal growth factor receptor levels in lipid rafts of human breast cancer cells. J Nutr 137(3): 548-553.
75. Altenburg JD, Farag SS (2015) The potential role of PD0332991 (Palbociclib) in the treatment of multiple myeloma. Expert Opin Investig Drugs 24(2): 261-271.
76. Corsetto PA, Cremona A, Montorfano G, Jovenitti IE, Orsini F, et al. (2012) Chemical-physical changes in cell membrane microdomains of breast cancer cells after omega-3 PUFA incorporation. Cell Biochem Biophys 64(1): 45-59.
77. Safwat S, Hathout RM, Ishak RA, Mortada ND (2017) Augmented simvastatin cytotoxicity using optimized lipid nanocapsules: a potential for breast cancer treatment. J Liposome Res 27(1): 1-10.
78. Wu Y, Wang Z, Liu G, Zeng X, Wang X, et al. (2015) Novel Simvastatin- Loaded Nanoparticles Based on Cholic Acid-Core Star-Shaped PLGA for Breast Cancer Treatment. J Biomed Nanotechnol 11(7): 1247-1260.