title: Relationship of p15 and p16 gene alterations to elevated dihydrofolate reductase in childhood acute lymphoblastic leukaemia.
abstract: The downstream effects of p15 and p16 gene deletions and loss of transcripts on dihydrofolate reductase (DHFR) were examined in 63 B-precursor (BP) acute lymphoblastic leukaemia (ALL) samples. p15 and/or p16 gene deletions were seen in 6% and 8%, respectively, of BP-ALL samples; however, losses of p15 and/or p16 transcripts were seen in 26 out of 63 (41%) samples. Loss of p15 transcripts (36.5%) exceeded that for p16 (17.5%). For the 26 BP-ALLs that lacked p15 and/or p16 transcripts, only six (23%) exhibited low levels of DHFR by flow cytometry assay with Pt430, a fluorescent anti-folate. Conversely, 18 out of 37 (49%) BP-ALL samples with intact p15 and/or p16 genes and transcripts showed low levels of DHFR (P = 0.04). In p15- and p16-null K562 cells transfected with a tetracycline-inducible p15 cDNA construct, induction of p15 transcripts and protein was accompanied by decreased growth rates, decreased S-phase fraction, decreased retinoblastoma protein phosphorylation, and markedly reduced levels of DHFR transcripts and protein. Collectively, our results suggest that losses of p15 and/or p16 gene expression result in elevated levels of DHFR in BP-ALL in children. However, additional downstream factors undoubtedly also contribute to elevated levels of this enzyme target.
authors.affiliation: Experimental and Clinical Therapeutics Program, Barbara Ann Karmanos Cancer Institute, Detroit, Michigan, USA.
authors.forename: S J
authors.initials: SJ
authors.lastname: Shah
authors.forename: J W
authors.initials: JW
authors.lastname: Taub
authors.forename: T L
authors.initials: TL
authors.lastname: Witt
authors.forename: B H
authors.initials: BH
authors.lastname: Pollock
authors.forename: B C
authors.initials: BC
authors.lastname: Ding
authors.forename: D S
authors.initials: DS
authors.lastname: Moore
authors.forename: M
authors.initials: M
authors.lastname: Amylon
authors.forename: J
authors.initials: J
authors.lastname: Pullen
authors.forename: Y
authors.initials: Y
authors.lastname: Ravindranath
authors.forename: L H
authors.initials: LH
authors.lastname: Matherly
mesh_terms: D000293:Adolescent; D015139:Blotting, Southern; D002051:Burkitt Lymphoma / Q000201:enzymology / Q000235:genetics*; D016022:Case-Control Studies; D002453:Cell Cycle; D018797:Cell Cycle Proteins; D002648:Child; D002675:Child, Preschool; D016001:Confidence Intervals; D050762:Cyclin-Dependent Kinase Inhibitor p15; D004305:Dose-Response Relationship, Drug; D004318:Doxycycline / Q000494:pharmacology; D005260:Female; D005434:Flow Cytometry; D017353:Gene Deletion; D015870:Gene Expression / Q000187:drug effects; D019942:Genes, p16; D006801:Humans; D007223:Infant; D020014:K562 Cells; D016015:Logistic Models; D008297:Male; D016017:Odds Ratio; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics*; D025521:Tumor Suppressor Proteins
chemical_list: C493966:CDKN2B protein, human; D018797:Cell Cycle Proteins; D050762:Cyclin-Dependent Kinase Inhibitor p15; D012333:RNA, Messenger; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D013762:Tetrahydrofolate Dehydrogenase; D004318:Doxycycline