大腸直腸癌是一種常見並且容易造成死亡的癌症。大約有三分之一的大腸直腸癌病人會發展成為轉移性的大腸直腸癌而且轉移後的大腸直腸癌往往是相關死亡的主要原因。所以迫切的了解大腸直腸癌的轉移分子機制，並找到新的治療標靶目標以及用於檢測和治療在具有大腸直腸癌轉移的病人的生物標記物是相當重要的。絲氨酸/蘇胺酸的蛋白質磷酸酶2A型(PP2A)，其完全酶的三聚體的組成分別是負責催化功能的C次單元，構成結構骨架的A次單元以及種類多變並負責受質選擇的B次單元。在此，我們探討了B56γ次單元成員中的B56γ3對於在大腸直腸癌細胞中上皮間質細胞轉換的角色。B56γ3在一系列的大腸直癌細胞當中表現不同的差異，其中以HCT116細胞株表達最高的B56γ3表現量。我們發現當B56γ3大量表達在HCT116和SW480的細胞當中，會增加一種關鍵的EMT誘導轉錄因子-Snail的表達，如果以核糖核酸干擾法降低B56γ3的表達則會減少Snail的表達。此外B56γ3大量表達在HCT116和SW480的細胞中時會稍微增加紡錘形態或是散射形態的細胞數，相反的，如果以核糖核酸干擾法降低B56γ3的表達則會減少這類形態的細胞數。為了更明瞭B56γ3對於細胞形態的調控，我們在HCT116細胞中使用CRISPR/Cas9的方法將能轉錄出B56γ3的基因PPP2R5C剔除掉，發現剔除掉PPP2R5C後的HCT116細胞，顯著的減少紡錘形態和散射形態，並增加HCT116細胞的上皮細胞形態。我們也進一步發現當B56γ3大量表達在HCT116和SW480的細胞中會顯著的增加細胞爬行和侵襲的能力，相反的，如果以核糖核酸干擾法降低B56γ3的表達或是基因剔除PPP2R5C則會顯著的降低細胞爬行和侵襲的能力。在分子機制上，我們發現B56γ3大量表達後會選擇性的增強AKT在T308的磷酸化，以核糖核酸干擾法降低B56γ3的表達則會降低AKT在T308的磷酸化。在HCT116和SW480的細胞中處理AKT抑制劑MK-2206或使用專一性針對AKT的siRNA來降低AKT的表達，發現會顯著的阻斷由B56γ3主導的Snail的表達量增加、HCT116和SW480的細胞爬行以及侵襲的能力。總結，PP2A的次單元B56γ3會增強AKT的活性來增加Snail的表達量並促進了大腸直腸癌的上皮間質細胞轉換。我們的研究前所未有的闡述了先前已被廣為認知的PP2A的腫瘤抑制調節次單元B56γ3具有在大腸直腸癌細胞中促進上皮間質細胞轉換的角色。

Colorectal cancer (CRC) is one of the most common human cancers, and is also one of the leading causes of cancer mortality. Approximately one-third of patients with CRC will develop metastatic diseases, and metastatic diseases are the major cause of CRC-related death. It is therefore urgent to better understand molecular mechanisms underlying metastasis of CRC and to find new therapeutic targets as well as biomarkers for detection and treatment for patients with CRC at risk of suffering metastatic diseases. The Ser/Thr protein phosphatase 2A (PP2A) holoenzyme is composed of a catalytic subunit (C), a structural subunit (A), and a highly variable regulatory subunit (B), which confers substrate specificity to PP2A. We investigated the role of B56γ3, the largest splice isoform of the B56γ, in epithelial-mesenchymal transition (EMT) of CRC cell lines. B56γ3 was differentially expressed in a series of CRC cell lines, and among the cell lines, HCT116 showed the highest levels of B56γ3 and SW480 showed moderate level of B56γ3. We found that B56γ3 overexpression increased levels of Snail, a key EMT-inducing transcriptional factor, whereas B56γ3 knockdown reduced levels of Snail in both HCT116 and SW480 cell lines. B56γ3 overexpression modestly increased the number of cells, whereas knockdown of B56γ3 reduced the number of cells with spindle-shaped and scattering morphology in both HCT116 and SW480 cell lines. To better observe the role of B56γ3 on EMT, we made PPP2R5C, which encodes B56γs, knockout clones of HCT116 cells by CRISPR/Cas9 approach, we found that B56γ knockout markedly reduced spindle-shaped and scattering morphology, and increased the epithelial morphology of HCT116 cells. Furthermore, B56γ3 overexpression significantly increased the migration and invasion ability, but knockdown of B56γ3 significantly reduced the migration and invasion ability of both HCT116 and SW480 cell lines. In addition, B56γ knockout markedly reduced the migration and invasion ability of HCT116 cells. Mechanistically, we found that B56γ3 overexpression selectively enhanced whereas knockdown of B56γ3 selectively reduced Thr308 phosphorylation, but not Ser473 phosphorylation, of AKT. Inhibition of AKT by AKT inhibitor MK-2206 or knockdown of AKT expression using siRNA specifically against AKT significantly blocked B56γ3-mediated increases in the level of Snail, the migration and invasion ability of both HCT116 and SW480 cell lines. In summary, the B56γ3 regulatory subunit of PP2A enhances AKT activity to increase Snail expression, and subsequently, promotes EMT of CRC cells. Our findings suggest an unprecedented role of a previously known tumor suppressor regulatory subunit of PP2A in promoting EMT of CRC cells.

1. Irrazábal T, Belcheva A, Girardin SE, Martin A, Philpott DJ. The multifaceted role of the intestinal microbiota in colon cancer. Mol Cell. 2014 Apr 24;54(2):309-20.
2. Sadikovic B, Al-Romaih K, Squire J.A, Zielenska M. Cause and consequences of genetic and epigenetic alterations in human cancer. Curr Genomics. 2008 Sep;9(6):394-408.
3. Ewing I, Hurley JJ, Josephides E, Millar A. The molecular genetics of colorectal cancer. Frontline Gastroenterol. 2014 Jan;5(1):26-30.
4. Pritchard CC, Grady WM. Colorectal cancer molecular biology moves into clinical practice. Gut. 2011 Jan;60(1):116-29.
5. Steeg PS. Targeting metastasis. Nature Rev Cancer. 2016 Apr;16(4):201-18.
6. Valastyan S, Weinberg RA. Tumor metastasis: molecular insights and evolving paradigms. Cell. 2011 Oct 14;147(2):275-92.
7. Van Cutsem E, Kohne CH, Hitre E, et al. Cetuximab and chemotherapy as initial treatment for metastatic colorectal cancer. N Engl J Med. 2009 Apr 2;360(14):1408-17.
8. Liao X, Lochhead P, Nishihara R, et al. Aspirin use, tumor PIK3CA mutation, and colorectal-cancer survival. N Engl J Med. 2012 Oct 25;367(17):1596-606.
9. Markowitz SD, Bertagnolli MM. Molecular origins of cancer: Molecular basis of colorectal cancer. N Engl J Med. 2009 Dec 17;361(25):2449-60.
10. Kastrinos F, Syngal S. Inherited colorectal cancer syndromes. Cancer J. 2011 Nov-Dec;17(6):405-15.
11. Sinicrope FA, Sargent DJ. Molecular pathways: microsatellite instability in colorectal cancer: prognostic, predictive, and therapeutic implications. Clin Cancer Res. 2012 Mar 15;18(6):1506-12.
12. Soreide K, Janssen EA, Soiland H, Korner H, Baak JP: Microsatellite instability in colorectal cancer. Br J Surg. 2006 Apr;93(4):395-406.
13. Nieuwenhuis MH, Vogt S, Jones N, Nielsen M, Hes FJ, Sampson JR, Aretz S, Vasen HF. Evidence for accelerated colorectal adenoma—carcinoma progression in MUTYH-associated polyposis? Gut. 2012 May;61(5):734-8.
14. Sakamoto S, Kyprianou N. Targeting anoikis resistance in prostate cancer metastasis. Mol Aspects Med. 2010 Apr;31(2):205-14.
15. Bissell MJ, Hines WC. Why don't we get more cancer? A proposed role of the microenvironment in restraining cancer progression. Nat. Med. 2011 Mar;17(3):320-9.
16. Kalluri R, Weinberg RA. The basics of epithelial-mesenchymal transition. J Clin Invest. 2009 Jun;119(6):1420-8.
17. Chaffer CL, Weinberg RA. Weinberg. A perspective on cancer cell metastasis. Science. 2011 Mar 25;331(6024):1559-64.
18. Davis FM, Stewart TA, Thompson EW, Monteith GR. Targeting EMT in cancer: opportunities for pharmacological intervention. Trends Pharmacol Sci. 2014 Sep;35(9):479-88.
19. Cohen P. The structure and regulation of protein phosphatases. Annu Rev Biochem. 1989; 58: 453-508.
20. Janssens V and Goris J. Protein phosphatase 2A: a highly regulated family of serine/threonine phosphatases implicated in cell growth and signalling. Biochem J. 2001 Feb 1;353(Pt 3):417-39.
21. Healy AM, Zolnierowicz S, Stapleton AE, Goebl M, Roach AA and Pringle JR. CDC55, a Saccharomyces cerevisiae gene involved in cellular morphogenesis: identification, characterization, and homology to the B subunit of mammalian type 2A protein phosphatase. Mol Cell Biol. 1991 Nov;11(11):5767-80.
22. McCright B and Virshup DM. Identification of a new family of protein phosphatase 2A regulatory subunits. J Biol Chem. 1995 Nov 3;270(44):26123-8.
23. Csortos C, Zolnierowicz S, Bakó E, Durbin SD, DePaoli-Roach AA. High complexity in the expression of the B' subunit of protein phosphatase 2A0. Evidence for the existence of at least seven novel isoforms. J Biol Chem. 1996 Feb 2;271(5):2578-88.
24. Tanabe O, Nagase T, et al. Molecular cloning of a 74-kDa regulatory subunit (B" or delta) of human protein phosphatase 2A. FEBS Lett. 1996 Jan 22;379(1):107-11.
25. Moreno CS, Park S, Nelson K, Ashby D, Hubalek F, Lane WS and Pallas DC. WD40 repeat proteins striatin and S/G (2) nuclear autoantigen are members of a novel family of calmodulin-binding proteins that associate with protein phosphatase 2A. J Biol Chem. 2000 Feb 25;275(8):5257-63.
26. Dagda RK, Zaucha JA, Wadzinski BE and Strack S. A developmentally regulated, neuron-specific splice variant of the variable subunit B beta targets protein phosphatase 2A to mitochondria and modulates apoptosis. J Biol Chem. 2003 Jul 4;278(27):24976-85.
27. McCright B, Rivers AM, Audlin S and Virshup DM. The B56 family of protein phosphatase 2A (PP2A) regulatory subunits encodes differentiation-induced phosphoproteins that target PP2A to both nucleus and cytoplasm. J Biol Chem. 1996 Sep 6;271(36):22081-9.
28. Strack S, Zaucha JA, Ebner FF, Colbran RJ and Wadzinski BE. Brain protein phosphatase 2A: developmental regulation and distinct cellular and subcellular localization by B subunits. J Comp Neurol. 1998 Mar 23;392(4):515-27.
29. Kuo YC, Huang KY, Yang CH, Yang YS, Lee WY and Chiang CW. Regulation of phosphorylation of Thr-308 of Akt, cell proliferation, and survival by the B55 alpha regulatory subunit targeting of the protein phosphatase 2A holoenzyme to Akt. J Biol Chem. 2008 Jan 25;283(4):1882-92.
30. Eichhorn PJ, Creyghton MP and Bernards R. Protein phosphatase 2A regulatory subunits and cancer. Biochim Biophys Acta. 2009 Jan;1795(1):1-15.
31. Arnold HK and Sears RC. Protein phosphatase 2A regulatory subunit B56 alpha associates with c-myc and negatively regulates c-myc accumulation. Mol Cell Biol. 2006 Apr;26(7):2832-44.
32. Li HH, Cai X, Shouse GP, Piluso LG and Liu X. A specific PP2A regulatory subunit, B56 gamma, mediates DNA damage-induced dephosphorylation of p53 at Thr55. EMBO J. 2007 Jan 24;26(2):402-11.
33. Eichhorn PJ, Creyghton MP and Bernards R. Protein phosphatase 2A regulatory subunits and cancer. Biochim Biophys Acta. 2009 Jan;1795(1):1-15.
34. Suganuma M, Fujiki H, Suguri H, Yoshizawa S, Hirota M, Nakayasu M, Ojika M, Wakamatsu K, Yamada K and Sugimura T. Okadaic acid: an additional non-phorbol-12-tetradecanoate-13-acetate-type tumor promoter. Proc Natl Acad Sci USA. 1988 Mar;85(6):1768-71.
35. Suganuma M, Fujiki H, Furuya-Suguri H, Yoshizawa S, Yasumoto S, Kato Y, Fusetani N and Sugimura T. Calyculin A, an inhibitor of protein phosphatases, a potent tumor promoter on CD-1 mouse skin. Cancer Res. 1990 Jun 15;50(12):3521-5.
36. Fujiki H and Suganuma M. Tumor promotion by inhibitors of protein phosphatases 1 and 2A: the okadaic acid class of compounds. Adv Cancer Res. 1993; 61:143-194.
37. McCright B, Rivers AM, Audlin S and Virshup DM. The B56 family of protein phosphatase 2A (PP2A) regulatory subunits encodes differentiation-induced phosphoproteins that target PP2A to both nucleus and cytoplasm. J Biol Chem. 1996 Sep 6;271(36):22081-9.
38. Eichhorn PJ, Creyghton MP and Bernards R. Protein phosphatase 2A regulatory subunits and cancer. Biochim Biophys Acta. 2009 Jan;1795(1):1-15.
39. Lechward K, Awotunde OS, Swiatek W and Muszynska G. Protein phosphatase 2A: variety of forms and diversity of functions. Acta Biochim Pol. 2001;48(4):921-33.
40. Chen W, Possemato R, Campbell KT, Plattner CA, Pallas DC and Hahn WC. Identification of specific PP2A complexes involved in human cell transformation. Cancer Cell. 2004 Feb;5(2):127-36.
41. Muneer S, Ramalingam V, Wyatt R, Schultz RA, Minna JD and Kamibayashi C. Genomic organization and mapping of the gene encoding the PP2A B56gamma regulatory subunit. Genomics. 2002 Mar;79(3):344-8.
42. Zheng H, Chen Y, Chen S, Niu Y, Yang L, Li B, Lu Y, Geng S, Du X and Li Y. Expression and distribution of PPP2R5C gene in leukemia. J Hematol Oncol. 2011 May 6;4:21.
43. McCright B, Brothman AR and Virshup DM. Assignment of human protein phosphatase 2A regulatory subunit genes B56alpha, B56beta, B56gamma, B56delta, and B56epsilon (PPP2R5A-PPP2R5E), highly expressed in muscle and brain, to chromosome regions 1q41, 11q12, 3p21, 6p21.1, and 7p11.2 --> p12. Genomics. 1996 Aug 15;36(1):168-70.
44. Varadkar P, Despres D, Kraman M, Lozier J, Phadke A, Nagaraju K and McCright B. The protein phosphatase 2A B56gamma regulatory subunit is required for heart development. Dev Dyn. 2014 Jun;243(6):778-90.
45. Arroyo JD and Hahn WC. Involvement of PP2A in viral and cellular transformation. Oncogene. 2005 Nov 21;24(52):7746-55.
46. Moreno CS, Ramachandran S, Ashby DG, Laycock N, Plattner CA, Chen W, Hahn WC and Pallas DC. Signaling and transcriptional changes critical for transformation of human cells by simian virus 40 small tumor antigen or protein phosphatase 2A B56gamma knockdown. Cancer Res. 2004 Oct 1;64(19):6978-88
47. Ito A, Kataoka TR, Watanabe M, Nishiyama K, Mazaki Y, Sabe H, Kitamura Y and Nojima H. A truncated isoform of the PP2A B56 subunit promotes cell motility through paxillin phosphorylation. EMBO J. 2000 Feb 15;19(4):562-71.
48. Chen W, Possemato R, Campbell KT, Plattner CA, Pallas DC and Hahn WC. Identification of specific PP2A complexes involved in human cell transformation. Cancer Cell. 2004 Feb;5(2):127-36.
49. Deichmann M, Polychronidis M, Wacker J, Thome M and Naher H. The protein phosphatase 2A subunit Bgamma gene is identified to be differentially expressed in malignant melanomas by subtractive suppression hybridization. Melanoma Res. 2001 Dec;11(6):577-85.
50. Arnold HK and Sears RC. Protein phosphatase 2A regulatory subunit B56alpha associates with c-myc and negatively regulates c-myc accumulation. Mol Cell Biol. 2006 Apr;26(7):2832-44.
51. Margolis SS, Perry JA, Forester CM, Nutt LK, Guo Y, Jardim MJ, Thomenius MJ, Freel CD, Darbandi R, Ahn JH, Arroyo JD, Wang XF, Shenolikar S, Nairn AC, Dunphy WG, Hahn WC, et al. Role for the PP2A/B56delta phosphatase in regulating 14-3-3 release from Cdc25 to control mitosis. Cell. 2006 Nov 17;127(4):759-73.
52. Bellacosa A, Testa JR, Staal SP, Tsichlis PN. A retroviral oncogene, Akt, encoding a serine-threonine kinase containing an SH2-like region. Science. 1991 Oct 11;254(5029):274-7.
53. Marte BM, Downward J. PKB/Akt: connecting phosphoinositide 3-kinase to cell survival and beyond, Trends Biochem. Trends Biochem Sci. 1997 Sep;22(9):355-8.
54. Hanada M, Feng J.H, Hemmings B.A, Structure, regulation and function of PKB/AKT — a major therapeutic target. Biochim Biophys Acta. 2004 Mar 11;1697(1-2):3-16.
55. Masure S, Haefner B, Wesselink J.J, Hoefnagel E, Mortier E, Verhasselt P, Tuytelaars A, Gordon R, Richardson A. Molecular cloning, expression and characterization of the human serine/threonine kinase Akt-3. Eur. J. Biochem. 1999 Oct 1;265(1):353-60.
56. Scheid MP, Woodgett JR. Unravelling the activation mechanisms of protein kinase B/Akt. FEBS Lett. 2003 Jul 3;546(1):108-12.
57. CallejaV, Alcor D, Laguerre M, Park J, Vojnovic B, Hemmings B.A, Downward J, Parker P.J, Larijani B. Intramolecular and intermolecular interactions of protein kinase B define its activation in vivo. PLoS Biol. 2007 Apr;5(4):e95
58. Calleja V, Laguerre M, Parker PJ, Larijani B. Role of a novel PH-kinase domain interface in PKB/Akt regulation: structural mechanism for allosteric inhibition. PLoS Biol. 2009 Jan 20;7(1):e17
59. Jethwa N, Chung GH, Lete MG, Alonso A, Byrne RD, Calleja V, Larijani B. Endomembrane PtdIns (3,4,5) P3 activates the PI3K-Akt pathway. J. Cell Sci. 2015 Sep 15;128(18):3456-65.
60. Kunkel MT, Ni Q, Tsien RY, Zhang J, Newton AC. Spatio-temporal dynamics of protein kinase B/Akt signaling revealed by a genetically encoded fluorescent reporter. J. Biol. Chem. 2005 Feb 18;280(7):5581-7.
61. Kuo YC, Huang KY, Yang CH, Yang YS, Lee WY, Chiang CW. Regulation of phosphorylation of Thr-308 of Akt, cell proliferation, and survival by the B55alpha regulatory subunit targeting of the protein phosphatase 2A holoenzyme to Akt. J. Biol. Chem. 2008 Jan 25;283(4):1882-92.
62. Brognard J, Sierecki E, Gao T, Newton AC. PHLPP and a second isoform, PHLPP2, differentially attenuate the amplitude of Akt signaling by regulating distinct Akt isoforms. Mol. Cell. 2007 Mar 23;25(6):917-31.
63. Chen M, Pratt CP, Zeeman M.E, Schultz N, Taylor B.S, Neill A’O, Castillo-Martin M, Nowak DG, Naguib A, Grace DM, et al. Identification of PHLPP1 as a tumor suppressor reveals the role of feedback activation in PTEN-mutant prostate cancer progression. Cancer Cell. 2011 Aug 16;20(2):173-86
64. Datta SR, Dudek H, Tao X, Masters S, Fu H, Gotoh Y, Greenberg ME. Akt phosphorylation of BAD couples survival signals to the cell-intrinsic death machinery. Cell. 1997 Oct 17;91(2):231-41.
65. del Peso L, González-García M, Page C, Herrera R, Nuñez G. Interleukin-3-induced phosphorylation of BAD through the protein kinase Akt. Science. 1997 Oct 24;278(5338):687-9.
66. Datta SR, Katsov A, Hu L, Petros A, Fesik SW, Yaffe MB, Greenberg ME. 14–3-3 proteins and survival kinases cooperate to inactivate BAD by BH3 domain phosphorylation. Mol. Cell. 2000 Jul;6(1):41-51.
67. Willis SN, Fletcher JI, Kaufmann T, van Delft MF, Chen L, Czabotar PE, Ierino H, Lee EF, Fairlie WD, Bouillet P, Strasser A, Kluck RM, Adams JM, Huang DC. Apoptosis initiated when BH3 ligands engage multiple Bcl-2 homologs, not Bax or Bak. Science. 2007 Feb 9;315(5813):856-9.
68. Mayo LD, Donner DB. A phosphatidylinositol 3-kinase/Akt pathway promotes translocation of Mdm2 from the cytoplasm to the nucleus. Proc Natl Acad Sci U S A. 2001 Sep 25;98(20):11598-603.
69. Zhou BP, Liao Y, Xia W, Zou Y, Spohn B, Hung MC. HER-2/neu induces p53 ubiquitination via Akt-mediated MDM2 phosphorylation. Nat. Cell Biol. 2001 Nov;3(11):973-82.
70. Manning1 BD and Cantley LW. AKT/PKB Signaling: Navigating Downstream. Cell. 2007 Jun 29;129(7):1261-74.
71. Liang J, Zubovitz J, Petrocelli T, Kotchetkov R, Connor MK, Han K, Lee JH, Ciarallo S, Catzavelos C, Beniston R, Franssen E, Slingerland JM. PKB/Akt phosphorylates p27, impairs nuclear import of p27 and opposes p27-mediated G1 arrest. Nat. Med. 2002 Oct;8(10):1153-60.
72. Shin I, Yakes FM, Rojo F, Shin NY, Bakin AV, Baselga J, Arteaga CL. PKB/Akt mediates cell-cycle progression by phosphorylation of p27(Kip1) at threonine 157 and modulation of its cellular localization. Nat. Med. 2002 Oct;8(10):1145-52.
73. Sekimoto T, Fukumoto M, Yoneda Y. 14–3-3 suppresses the nuclear localization of threonine 157-phosphorylated p27(Kip1). EMBO J. 2004 May 5;23(9):1934-42.
74. Medema RH, Kops GJ, Bos JL, Burgering BM. AFX-like Forkhead transcription factors mediate cell-cycle regulation by Ras and PKB through p27kip1. Nature. 2000 Apr 13;404(6779):782-7.
75. Zhou BP, Liao Y, Xia W, Spohn B, Lee MH, Hung MC. Cytoplasmic localization of p21Cip1/WAF1 by Akt-induced phosphorylation in HER-2/neu-overexpressing cells. Nat. Cell Biol. 2001 Mar;3(3):245-52.
76. Manning BD. Balancing Akt with S6K: implications for both metabolic diseases and tumorigenesis. J Cell Biol. 2004 Nov 8; 167(3):399-403.
77. Harrington LS, Findlay GM, Gray A, Tolkacheva T, Wigfield S, Rebholz H, Barnett J, Leslie NR, Cheng S, Shepherd PR, Gout I, Downes CP, Lamb RF. The TSC1-2 tumor suppressor controls insulin-PI3K signaling via regulation of IRS proteins. J Cell Biol. 2004 Jul 19; 166(2):213-23
78. Shah OJ, Hunter T. Turnover of the active fraction of IRS1 involves raptor-mTOR- and S6K1-dependent serine phosphorylation in cell culture models of tuberous sclerosis. Mol Cell Biol. 2006 Sep; 26(17):6425-34.
79. Tzatsos A, Kandror KV. Nutrients suppress phosphatidylinositol 3-kinase/Akt signaling via raptor-dependent mTOR-mediated insulin receptor substrate 1 phosphorylation. Mol Cell Biol. 2006 Jan; 26(1):63-76.
80. Manning BD, Cantley LC. AKT/PKB signaling: navigating downstream. Cell. 2007 Jun 29;129(7):1261-74.
81. Altomare DA, Testa JR. Perturbations of the AKT signaling pathway in human cancer. Oncogene. 2005 Nov 14;24(50):7455-64.
82. Chan CH, Jo U, Kohrman A, Rezaeian AH, Chou PC, Logothetis C, et al. Posttranslational regulation of AKT in human cancer. Cell Biosci. 2014 Oct 1;4(1):59.
83. Ahmed NN, Franke TF, Bellacosa A, Datta K, Gonzalez‐Portal ME, Taguchi T, et al The proteins encoded by c‐AKT and v‐AKT differ in post‐translational modification, subcellular localization and oncogenic potential. Oncogene. 1993 Jul;8(7):1957-63.
84. Yang WK, Wu CY, Wu J, Lin HK. Regulation of AKT signaling activation by ubiquitination. Cell Cycle. 2010 Feb 1;9(3):487-97.
85. Sun M, Wang G, Paciga JE, Feldman RI, Yuan ZQ, Ma XL, Shelley SA, Jove R, Tsichlis PN, Nicosia SV and Cheng JQ. AKT1/PKBalpha kinase is frequently elevated in human cancers and its constitutive activation is required for oncogenic transformation in NIH3T3 cells. Am. J. Pathol. 2001 Aug;159(2):431-7.
86. Yuan ZQ, Sun M, Feldman RI, Wang G, Ma X, Jiang C, Coppola D, Nicosia SV and Cheng JQ. Frequent activation of AKT2 and induction of apoptosis by inhibition of phosphoinositide-3-OH kinase/Akt pathway in human ovarian cancer. Oncogene. 2000 May 4;19(19):2324-30.
87. Altomare DA, Tanno S, De Rienzo A, Klein-Szanto A, Skele KL, Hoffman JP and Testa JR. (2003). Frequent activation of AKT2 kinase in human pancreatic carcinomas. J. Cell. Biochem. 2002;87(4):470-6.
88. Nakatani K, Thompson DA, Barthel A, Sakaue H, Liu W, Weigel RJ and Roth RA. Up-regulation of Akt3 in estrogen receptor-deficient breast cancers and androgen-independent prostate cancer lines. J Biol Chem. 1999 Jul 30;274(31):21528-32.
89. Lin HJ, Jin Y, Castle VP, Nunez G, Huang M and Lin J. Overexpression of Akt/AKT can modulate chemotherapy-induced apoptosis. Anticancer Res. 2000 Jan-Feb;20(1A):407-16.
90. Alessi DR, James SR, Downes CP, Holmes AB, Gaffney PR, Reese CB, Cohen P. Characterization of a 3-phosphoinositide-dependent protein kinase which phosphorylates and activates protein kinase B alpha. Curr Biol. 1997 Apr 1; 7(4):261-9.
91. Vanhaesebroeck B, Alessi DR. The PI3K-PDK1 connection: more than just a road to PKB. Biochem J. 2000 Mar 15; 346 Pt 3:561-76.
92. Sarbassov DD, Guertin DA, Ali SM, Sabatini DM. Phosphorylation and regulation of Akt/PKB by the rictor-mTOR complex. Science. 2005 Feb 18; 307(5712):1098-101.
93. David O, Jett J, LeBeau H, Dy G, Hughes J, Friedman M, Brody AR. Phospho-Akt overexpression in non-small cell lung cancer confers significant stage-independent survival disadvantage. Clin Cancer Res. 2004 Oct 15; 10(20):6865-71.
94. Tang JM, He QY, Guo RX, Chang XJ. Phosphorylated Akt overexpression and loss of PTEN expression in non-small cell lung cancer confers poor prognosis. Lung Cancer. 2006 Feb; 51(2):181-91.
95. Lim WT, Zhang WH, Miller CR, Watters JW, Gao F, Viswanathan A, Govindan R, McLeod HL. PTEN and phosphorylated AKT expression and prognosis in early- and late-stage non-small cell lung cancer. Oncol Rep. 2007 Apr; 17(4):853-7.
96. Mukohara T, Kudoh S, Yamauchi S, Kimura T, Yoshimura N, Kanazawa H, Hirata K, Wanibuchi H, Fukushima S, Inoue K, Yoshikawa J. Expression of epidermal growth factor receptor (EGFR) and downstream-activated peptides in surgically excised non-small-cell lung cancer (NSCLC). Lung Cancer. 2003 Aug; 41(2):123-30.
97. Tsao AS, McDonnell T, Lam S, Putnam JB, Bekele N, Hong WK, Kurie JM. Increased phospho-AKT (Ser(473)) expression in bronchial dysplasia: implications for lung cancer prevention studies. Cancer Epidemiol Biomarkers Prev. 2003 Jul; 12(7):660-4.
98. Massion PP, Taflan PM, Shyr Y, Rahman SM, Yildiz P, Shakthour B, Edgerton ME, Ninan M, Andersen JJ, Gonzalez AL. Early involvement of the phosphatidylinositol 3-kinase/Akt pathway in lung cancer progression. Am J Respir Crit Care Med. 2004 Nov 15; 170(10):1088-94.
99. Tsurutani J, Fukuoka J, Tsurutani H, Shih JH, Hewitt SM, Travis WD, Jen J, Dennis PA. Evaluation of two phosphorylation sites improves the prognostic significance of Akt activation in non-small-cell lung cancer tumors. J Clin Oncol. 2006 Jan 10; 24(2):306-14.
100. Gallay N, Dos Santos C, Cuzin L, Bousquet M, Simmonet Gouy V, Chaussade C, Attal M, Payrastre B, Demur C, Récher C. The level of AKT phosphorylation on threonine 308 but not on serine 473 is associated with high-risk cytogenetics and predicts poor overall survival in acute myeloid leukemia. Leukemia. 2009 Jun; 23(6):1029-38.
101. Pearce LR, Komander D, Alessi DR. The nuts and bolts of AGC protein kinases. Nat Rev Mol Cell Biol. 2010 Jan; 11(1):9-22.
102. Feng J, Park J, Cron P, Hess D, Hemmings BA. Identification of a PKB/Akt hydrophobic motif Ser-473 kinase as DNA-dependent protein kinase. J Biol Chem. 2004 Sep 24; 279(39):41189-96.
103. Lai TY, Yen CJ, Tsai HW, Yang YS, Hong WF, Chiang CW. The B56γ3 regulatory subunit-containing protein phosphatase 2A outcompetes Akt to regulate p27KIP1 subcellular localization by selectively dephosphorylating phospho-Thr157 of p27KIP1. Oncotarget. 2016 Jan 26;7(4):4542-58.
104. American Cancer Society. Colorectal Cancer Facts & Figures 2017-2019. Atlanta, Ga: American Cancer Society; 2017.
105. Libutti SK, Salz LB, Willett CG, Levine RA. Chapter 57,60: Cancer of the colon. In: DeVita VT, Lawrence TS, Rosenberg SA, eds. DeVita, Hellman, and Rosenberg’s Cancer: Principles and Practice of Oncology. 10th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2015.
106. Sigurdson ER, Benson AB, Minsky B. Cancer of the rectum. In: Niederhuber JE, Armitage JO, Dorshow JH, Kastan MB, Tepper JE, eds. Abeloff’s Clinical Oncology. 5th ed. Philadelphia, Pa. Elsevier: 2014: 1336-1359.
107. Steele SR, Johnson EK, Champagne B. Endoscopy and polyps-diagnostic and therapeutic advances in management. World J Gastroenterol 2013; 19(27): 4277-4288.
108. Van Schaeybroeck S, Lawler M, Johnston B, et al. Colorectal cancer. In: Neiderhuber JE, Armitage JO, Doroshow JH, Kastan MB, Tepper JE, eds. Abeloff’s Clinical Oncology. 5th ed. Philadelphia, Pa: Elsevier; 2014: 1278-1335.
109. Sipos F, Galamb O. Epithelial‐to‐mesenchymal and mesenchymal‐to‐epithelial transitions in the colon. World J Gastroenterol. 2012 Feb 21;18(7):601-8.
110. Winston JT, Strack P, Beer-Romero P, Chu CY, Elledge SJ, Harper JW. The SCFbeta-TRCP-ubiquitin ligase complex associates specifically with phosphorylated destruction motifs in IkappaBalpha and beta-catenin and stimulates IkappaBalpha ubiquitination in vitro. Genes Dev. 1999 Feb 1;13(3):270-83.
111. Julien S, Puig I, Caretti E, Bonaventure J, Nelles L, van Roy F, Dargemont C, de Herreros AG, Bellacosa A, Larue L. Activation of NF-kappaB by Akt upregulates Snail expression and induces epithelium mesenchyme transition. Oncogene. 2007 Nov 22;26(53):7445-56.
112. Grille SJ, Bellacosa A, Upson J, et al. The protein kinase Akt induces epithelial mesenchymal transition and promotes enhanced motility and invasiveness of squamous cell carcinoma lines. Cancer Res. 2003 May 1;63(9):2172-8.
113. Lee TY, Lai TY, Lin SC, Wu CW, Ni IF, Yang YS, Hung LY, and Chiang CW. The B56γ3 Regulatory Subunit of Protein Phosphatase 2A (PP2A) Regulates S Phase-specific Nuclear Accumulation of PP2A and the G1 to S Transition. J Biol Chem. 2010 Jul 9;285(28):21567-80.