Methylthioadenosine (MTA) Rescues Methylthioadenosine Phosphorylase (MTAP)-Deficient Tumors from Purine Synthesis Inhibition in Vivo via Non-Autonomous Adenine Supply

Astrid Ruefli-Brasse, Doreen Sakamoto, Jessica Orf, Minqing Rong, Jianxia Shi, Tim Carlson, Kim Quon, Alexander Kamb, Dineli Wickramasinghe

.

DOI: 10.4236/jct.2011.24072                

Abstract

Methylthioadenosine phosphorylase, (MTAP) is a key enzyme in the adenine and methionine salvage pathways. MTAP is encoded on human chromosome 9p21 in close proximity to the p16INK4a and p14ARF tumor suppressor genes and is frequently co-deleted with p16INK4a in many cancers. Deletion of MTAP has been reported to create a reliance of MTAP^–/– tumors on de novo purine synthesis to maintain adequate pools of AMP, leading to increased sensitivity to purine synthesis inhibitors, such as L-alanosine. The ‘Achilles heel’ created by the loss of MTAP in cancer cells provides a unique therapeutic opportunity whereby MTAP^–/– tumors could be selectively targeted with purine synthesis inhibitors and normal tissues could be preferentially rescued with MTAP substrates, such as MTA. We demonstrate that, in contrast to published literature, MTAP^–/– cells are not more sensitive to inhibition of de novo purine synthesis than MTAP^+/+ cells. Although MTA can preferentially rescue MTAP^+/+ cells from purine-synthesis inhibitor toxicity in vitro, MTA protects cells of both genotypes from L-alanosine equivalently in vivo. Our data demonstrate that in vivo, adenine salvaged from plasma and adjacent tissues is sufficient to protect MTAP^–/– tumors from the effects of purine synthesis inhibitors. These results suggest targeting MTAP^–/– tumors with de novo purine synthesis inhibitors is unlikely to provide significant benefit over other therapeutic strategies and may explain, at least in part, the lack of efficacy of L-alanosine in clinical trials.

Keywords

Methylthioadenosine Phosphorylase, Purine Metabolism, L-Alanosine, Adenine Salvage

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	L. Christa, L. Thuillier, A. Munier and J. L. Perignon, “Salvage of 5’-Deoxy-methylthioadenosine into Purines and Methionine by Lymphoid Cells and Inhibition of Cell Proliferation,” Biochimica et Biophysica Acta, Vol. 803, No. 1-2, 1984, pp. 7-10. doi:10.1016/0167-4889(84)90048-X
[2]	A. E. Pegg and H. G. Williams-Ashman, “Phosphate-Stimulated Breakdown of 5’-Methylthioadenosine by Rat Ventral Prostate,” Biochemical Journal, Vol. 115, 1969, pp. 241-247.
[3]	P. S. Backlund Jr. and R. A. Smith, “Methionine Synthesis from 5’-Methylthioadenosine in Rat Liver,” Journal of Biological Chemistry, Vol. 256, 1981, pp. 1533-1535.
[4]	T. W. Stone and H. A. Simmonds, “Purines: Basic and Clinical Aspects,” Kluwer Academic Publishers, Dordrecht, 1991. doi:10.1007/978-94-011-3911-3
[5]	N. Kamatani and D. A. Carson, “Dependence of Adenine Production upon Polyamine Synthesis in Cultured Human Lymphoblasts,” Biochim Biophys Acta, Vol. 675, 1981, pp. 344-350.
[6]	A. L. Subhi, P. Diegelman, C. W. Porter, B. Tang, Z. J. Lu, G. D. Markham and W. D. Kruger, “Methylthioa-denosine Phosphorylase Regulates Ornithine Decarboxylase by Production of Downstream Metabolites,” Journal of Biological Chemistry, Vol. 278, 2003, pp. 49868-49873. doi:10.1074/jbc.M308451200
[7]	A. Batova, M. B. Diccianni, T. Nobori, T. Vu, J. Yu, L. Bridgeman and A. L. Yu, “Frequent Deletion in the Methylthioadenosine Phosphorylase Gene in T-Cell Acute Lymphoblastic Leukemia: Strategies for Enzyme-Targeted Therapy,” Blood, Vol. 88, 1996, pp. 3083-3090.
[8]	T. Nobori, J. G. Karras, F. Della Ragione, T. A. Waltz, P. P. Chen and D. A. Carson, “Absence of Methylthioa-denosine Phosphorylase in Human Gliomas,” Cancer Research, Vol. 51, 1991, pp. 3193-3197.
[9]	T. Nobori, K. Takabayashi, P. Tran, L. Orvis, A. Batova, A. L. Yu and D. A. Carson, “Genomic Cloning of Methylthioadenosine Phosphorylase: A Purine Metabolic Enzyme Deficient in Multiple Different Cancers,” Proceedings of the National Academy of Sciences of the United States of America, Vol. 93, No. 12, 1996, pp. 6203-6208. doi:10.1073/pnas.93.12.6203
[10]	A. Batova, M. B. Diccianni, M. Omura-Minamisawa, J. Yu, C. J. Carrera, L. J. Bridgeman, F. H. Kung, J. Pullen, M. D. Amylon and A. L. Yu, “Use of Alanosine as a Methylthioadenosine Phosphorylase-Selective Therapy for T-Cell Acute Lymphoblastic Leukemia in Vitro,” Cancer Research, Vol. 59, 1999, pp. 1492-1497.
[11]	Z. H. Chen, O. I. Olopade and T. M. Savarese, “Expression of Methylthioadenosine Phosphorylase cDNA in p16-, MTAP-Malignant Cells: Restoration of Methylthioadenosine Phosphorylase-Dependent Salvage Pathways and Alterations of Sensitivity to Inhibitors of Purine De Novo Synthesis,” Molecular Pharmacology, Vol. 52, 1997, pp. 903-911.
[12]	A. Batova, H. Cottam, J. Yu, M. B. Diccianni, C. J. Carrera and A. L. Yu, “EFA (9-Beta-D-erythrofuranosyladenine) Is an Effective Salvage Agent for Methylthioadenosine Phosphorylase-Selective Therapy of T-Cell Acute Lymphoblastic Leukemia with L-Alanosine,” Blood, Vol. 107, No. 3, 2006, pp. 898-903. doi:10.1182/blood-2005-06-2430
[13]	C. Rago, B. Vogelstein and F. Bunz, “Genetic Knockouts and Knockins in Human Somatic Cells,” Nature Protocols, Vol. 2, 2007, pp. 2734-2746. doi:10.1038/nprot.2007.408
[14]	S. Swift, J. Lorens, P. Achacoso and G. P. Nolan, “Rapid Production of Retroviruses for Efficient Gene Delivery to Mammalian Cells Using 293T Cell-Based Systems,” Current Protocols in Immunology, 2001, Unit 10.17C.
[15]	P. J. Casey and J. M. Lowenstein, “Inhibition of Adenylosuccinate Lyase by L-Alanosyl-5-aminoimidazole-4-carboxylic Acid Ribonucleotide (Alanosyl-Aicor),” Biochemical Pharmacology, Vol. 36, No. 5, 1987, pp. 705-709. doi:10.1016/0006-2952(87)90722-2
[16]	A. K. Tyagi and D. A. Cooney, “Identification of the Antimetabolite of L-Alanosine, L-Alanosyl-5-amino-4-imidazole-carboxylic Acid Ribonucleotide, in Tumors and Assessment of Its Inhibition of Adenylosuccinate Synthetase,” Cancer Research, Vol. 40, 1980, pp. 4390-4397.
[17]	C. H. Takimoto, “New Antifolates: Pharmacology and Clinical Applications,” Oncologist, Vol. 1, 1996, pp. 68-81.
[18]	S. Coulthard and L. Hogarth, “The Thiopurines: An Update,” Investigational New Drugs, Vol. 23, No. 6, 2005, pp. 523-532. doi:10.1007/s10637-005-4020-8
[19]	N. Kamatani, W. A. Nelson-Rees and D. A. Carson, “Selective Killing of Human Malignant Cell Lines Deficient in Methylthioadenosine Phosphorylase, a Purine Metabolic Enzyme,” Proceedings of the National Academy of Sciences of the United States of America, Vol. 78, No. 2, 1981, pp. 1219-1223. doi:10.1073/pnas.78.2.1219
[20]	G. M. Dosik, D. Stewart, M. Valdivieso, M. A. Burgess and G. P. Bodey, “Phase I Study of L-Alanosine Using a Daily x 3 Schedule,” Cancer Treatment Reports, Vol. 66, 1982, pp. 73-76.
[21]	H. L. Kindler, H. A. Burris, A. B. Sandler and I. A. Oliff, “A Phase II Multicenter Study of L-Alanosine, a Potent Inhibitor of Adenine Biosynthesis, in Patients with MTAP-Deficient Cancer,” Investigational New Drugs, Vol. 27, No. 1, 2009, pp. 75-81. doi:10.1007/s10637-008-9160-1
[22]	R. Munshi, A. S. Clanachan and H. P. Baer, “5’-Deoxy-5’-methylthioadenosine: A Nucleoside Which Differentiates between Adenosine Receptor Types,” Biochemical Pharmacology, Vol. 37, No. 10, 1988, pp. 2085-2089. doi:10.1016/0006-2952(88)90560-6
[23]	R. A. Olsson, E. M. Khouri, J. L. Bedynek Jr. and J. McLean, “Coronary Vasoactivity of Adenosine in the Conscious Dog,” Circulation Research, Vol. 45, 1979, pp. 468-478.
[24]	M. K. Riscoe and A. J. Ferro, “5-Methylthioribose. Its effects and Function in Mammalian Cells,” Journal of Biological Chemistry, Vol. 259, 1984, pp. 5465-5471.
[25]	A. K. Tyagi, D. C. Thake, E. McGee and D. A. Cooney, “Determinants of the Toxicity of L-Alanosine to Various Organs of the Mouse,” Toxicology, Vol. 21, No. 1, 1981, pp. 59-69. doi:10.1016/0300-483X(81)90016-0
[26]	J. Yu, A. Batova, L. Shao, C. J. Carrera and A. L. Yu, “Presence of Methylthioadenosine Phosphorylase (MTAP) in Hematopoietic Stem/Progenitor Cells: Its Therapeutic Implication for MTAP (-) Malignancies,” Clinical Cancer Research, Vol. 3, 1997, pp. 433-438.