ras oncogene activation and occupational exposures in acute myeloid leukemia

Abstract

Background: Epidemiologic studies of acute myeloid leukemias (AMLs) show small increases in risk of disease associated with certain occupations and chemical exposures.

Purpose: This study was designed to determine whether the presence of mutationally activated ras oncogenes in AML are associated with occupational and chemical exposures.

Methods: We interviewed 62 patients with newly diagnosed AML (or their next-of-kin), all of whom were enrolled in a national multicenter clinical trial, and 630 healthy control subjects. DNA extracted from patients' pretreatment bone marrow samples was amplified by using the polymerase chain reaction and probed with allele-specific oligonucleotides for activating point mutations at the 12th, 13th, and 61st codons of three protooncogenes: H-ras (also known as HRAS), K-ras (also known as KRAS2), and N-ras (also known as NRAS).

Results: Patients with ras mutation-positive AML had a higher frequency (six of 10 patients) of working 5 or more years in an a priori high-risk occupation than did patients with ras mutation-negative AML (eight of 52; odds ratio [OR] = 6.8; 95% confidence interval [CI] = 1.3-36). Patients with ras mutation-positive AML were more likely than patients with ras mutation-negative AML to have breathed chemical vapor on the job (OR = 9.1; 95% CI = 1.3-64) or to have had skin contact with chemicals (OR = 6.9; 95% CI = 1.3-37). When ras-positive patients were compared with healthy control subjects, the ORs for occupation and occupational exposures remained elevated, while patients with ras mutation-negative AML showed no increased risk when compared with control subjects.

Conclusion: Activation of ras proto-oncogenes may identify an etiologic subgroup of AML caused by occupation and chemical exposure.

Implication: Disease etiology may be better understood if epidemiologic measures of exposure are integrated with molecular assays of the genetic defects responsible for cancer initiation and promotion.