Timothy Steele Ph.D.

Research narrative

Introduction

Human natural killer (NK) cells are a population of lymphocytes which can lyse tumor target cells in vitro without prior sensitization and with no major histocompatibility complex restriction. In the body, these cells act as the first line of defense against virus-infected cells.

The YT cell line is an interleukin-2-independent human leukemia NK-like cell line that has been used in numerous studies to investigate natural killer cell function. YT cells were isolated originally from a 15 year old boy with acute lymphoblastic lymphoma. Our laboratory has been using a derivative of the YT cell line, YT-INDY, to investigate new treatment strategies for this type of leukemia. Clinically, although NK cell leukemias in patients are relatively rare, they tend to be aggressive and very difficult to treat. Consequently, patient outcomes show that the mortality rate is quite high. Insight gleaned from the research in this proposal might contribute to better therapeutic approaches to these types of cancers.

Statin drugs are very effective for lowering LDL cholesterol levels and have a limited number of short-term side effects. Their mechanism of action relies on interrupting the formation of cholesterol by inhibiting HMG-CoA reductase, which is responsible for controlling the rate of cholesterol production. In addition, statins increase the ability of the liver to remove LDL-cholesterol that is present in the blood. It is not unusual for the LDL-cholesterol levels to drop by 20-60% in statin-treated patients. Commonly prescribed statins include lovastatin (Mevacor™), simvastatin (Zocor™), atorvastatin (Lipitor™), fluvastatin (Lescol™), pravastatin (Pravachol™), and rosuvastatin calcium (Crestor™).

Aside from their effects on LDL-cholesterol, statins have been shown to inhibit the growth of several commonly used leukemic cell lines. In our hands, several statins were able to inhibit several cell YT-INDY cell functions, including cell growth. The novel effect of statins on leukemia cells is a new, and potentially exciting, field of research.

Preliminary Results

Preliminary investigations have shown that:

Statins profoundly inhibit the natural killer cell cytotoxicity of YT-INDY, but the inhibition can be reversed with mevalonate and GGPP. Other mevalonate pathway intermediates, such as FPP, DMPP, IPP, or squalene, could not reverse the inhibition.
Intermediate-to-high levels of statins decrease the proliferative response of YT-INDY. Mevalonate and GGPP can restore cell proliferation to near control values.
Statins reduce the percentage of cells in the S phase of the cell cycle and increase the percentage of cells in the G0/G1 phase. Mevalonate can fully restore control levels of cells in each phase of the cell cycle, while GGPP can partially restore the cell levels.
ERK1/ERK2 phosphorylation is reduced in statin-treated YT-INDY, indicating that statins can exert a suppressive effect on this MAP kinase pathway. Mevalonate can reverse the statin-induced suppression of ERK1/ERK2 phosphorylation.

Selected Publications

Steele, T.A. and Hauser, C.C. (2005) Role of Interferon-α in a successful murine tumor therapy. Exp. Biol. Med. 230: 487-493.
Young H.E., Duplaa C., Yost M.J., Henson N.L., Floyd J.A., Detmer K., Thompson A.J., Powell S.W., Gamblin T.C., Kizziah K., Holland B.J., Boev A., Van De Water J.M., Godbee D.C., Jackson S., Rimando M., Edwards C.R., Wu E., Cawley C., Edwards P.D., Macgregor A., Bozof R., Thompson T.M., Petro G.J. Jr, Shelton H.M., McCampbell B.L., Mills J.C., Flynt F.L., Steele T.A., et al. (2004) Clonogenic analysis reveals reserve stem cells in postnatal mammals. II. Pluripotent epiblastic-like stem cells. Anatomical Record 277A: 178-203.
Young H.E., Duplaa C., Romero-Ramos M., Chesselet M.F., Vourc'h P., Yost M.J., Ericson K., Terracio L., Asahara T., Masuda H., Tamura-Ninomiya S., Detmer K., Bray R.A., Steele T.A., et al. (2004) Adult reserve pluripotent stem cells and their potential for tissue engineering. Cell Biochem. Biophys. 40: 1-80.
Shackelford, R.E., Mansuszak, R.P., Johnson, C.D., Hellrung, D.J., Steele, T.A., Link, C.J., and Wang, S. (2003) Desferrioxamine treatment increases the genomic stability of Ataxia-telangiectasia cells. DNA Repair 2: 971-981.
Steele, T.A. (2002) Clinical significance of interleukin-18. Leuk. Res. 26: 975-976.
Steele, T.A. (2002) Role of oncolytic viruses in cancer treatment modalities. Comments on Theoretical Biol. 7: 35-52.
Steele, T.A. (2002) Chemotherapy-induced immunosuppression and reconstitution of immune function. Leuk. Res. 26: 107-110.
Mawson, T. and Steele, T.A. (2001) Possible role of retinoids in hepatitis B virus-associated liver damage. Exp. Biol. Med. 226: 734-739.
Young, H.E., Steele, T.A., Bray, R.A., Hudson, J., Floyd, J.A., Hawkins, K., Thomas, K., Austin, T., Edwards, C., Cuzzourt, J., Duenzl, M., Lucas, P.A. and Black, Jr., A.C. (2001) Human reserve pluripotent mesenchymal stem cells are present in the connective tissues of skeletal muscle and dermis from fetal, adult, and geriatric donors. Anat. Record 264: 51-62.
Steele, T.A. and Carpenter, S.S. (2000) Immunotherapeutic strategies for ovarian cancer. Mod. Asp. Immunobiol. 1: 131-135.
K. Detmer, A.N. Walker, T.M. Jenkins, T.A. Steele and H. Dannawi. (2000) Erythroid differentiation in vitro is blocked by cyclopamine, an inhibitor of Hedgehog signaling. Blood Cells, Molecules, and Diseases. Blood Cells Mol. Dis. 26: 360-372.
Steele, T.A. (2000) Recent developments in the virus therapy of cancer. Proc. Soc. Exp. Biol. Med. 223: 118-127.
Detmer, K., Steele, T.A., Shoop, M., Dannawi, H. (1999) Lineage-restricted expression of the bone morphogenetic protein-7 and placental bone morphogenetic protein genes in human hematopoietic cell lines. Blood Cells Mol. Dis. 25: 310-323.
Young, H. E., Steele, T.A., Bray, R. A., Detmer, K., Blake, L. W., Lucas, P. A., and Black, Jr, A. C. (1999) Human pluripotent and progenitor cells display cell surface cluster differentiation markers CD10, CD13, CD56 and MHC class-I. Proc. Soc. Exp. Biol. Med. 221: 63-71.
Steele, T.A. and Cox, D. C. (1996). Elimination of EL-4 and L1210 murine tumors by 1,3-bis (2-chloroethyl)-1-nitrosourea requires an intact immune response. Proc. Soc. Exper. Biol. Med. 212: 63-68.
Al-Sheboul, S., Crosely, D. and Steele, T.A. (1996). Inhibition of reovirus-stimulated murine natural killer cell cytotoxicity by cyclosporine. Life Sci. 59: 1675-1682.
Steele, T.A. and Cox, D. C. (1995). Reovirus type 3 chemoimmunotherapy of murine lymphoma is abrogated by cyclosporine. Cancer Biother. 10: 307-315.
Steele, T.A. and Brahmi, Z. (1989). Phosphatidylinositol metabolism in tumor target cell-stimulated human natural killer cells. In: Natural Killer Cells and Host Defense (E. W. Ades and C. Lopez, ed.) p. 167-171. S. Karger Publishers, Inc., New York.
Steele, T.A. and Brahmi, Z. (1988). Inhibition of human natural killer cell activity by the protein kinase C inhibitor 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7) is an early but postbinding event. J. Immunol. 141: 3164-3169.
Steele, T.A. and Brahmi, Z. (1988). Phosphatidylinositol metabolism accompanies early activation events in tumor target cell-stimulated human natural killer cells. Cell. Immunol. 112: 402-413.
Steele, T.A. and Brahmi, Z. (1988). Chlorpromazine inhibits human natural killer cell activity and antibody-dependent cell-mediated cytotoxicity. Biochem. Biophys. Res. Comm. 155: 597-602.