1. ¹Department of Microbiology-Immunology, Kimmel Cancer Center, Jefferson Medical College, Philadelphia, USA
2. ²Department of Medicine, Kimmel Cancer Center, Jefferson Medical College, Philadelphia, USA
3. ³Oncology Drug Discovery, Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, NJ, USA
4. ⁴Department of Radiation Oncology, Kimmel Cancer Center, Jefferson Medical College, Philadelphia, USA

Correspondence: K Huebner, Kimmel Cancer Center, BLSB, Room 1008, 233 S. 10th Street, Philadelphia, PA 19107, USA. E-mail: Kay.Huebner@mail.jci.tju.edu

⁵Current address: School of Veterinary Medicine, University of Pennsylvania, 38th and Spruce, Philadelphia, PA 19104, USA

⁶These authors contributed equally to this work

Received 22 January 2004; Revised 25 May 2004; Accepted 7 June 2004; Published online 19 October 2004.

Abstract

To identify functions of the fragile tumour suppressor gene, FHIT, matched pairs of Fhit-negative and -positive human cancer cell clones, and normal cell lines established from Fhit -/- and +/+ mice, were stressed and examined for differences in cell cycle kinetics and survival. A larger fraction of Fhit-negative human cancer cells and murine kidney cells survived treatment with mitomycin C or UVC light compared to matched Fhit-positive cells; 10-fold more colonies of Fhit-deficient cells survived high UVC doses in clonigenic assays. The human cancer cells were synchronised in G1, released into S and treated with UVC or mitomycin C. At 18 h post mitomycin C treatment 6-fold more Fhit-positive than -negative cells had died, and 18 h post UVC treatment 3.5-fold more Fhit-positive cells were dead. Similar results were obtained for the murine -/- cells. After low UVC doses, the rate of DNA synthesis in -/- cells decreased more rapidly and steeply than in +/+ cells, although the Atr–Chk1 pathway appeared intact in both cell types. UVC surviving Fhit -/- cells appear transformed and exhibit >5-fold increased mutation frequency. This increased mutation burden could explain the susceptibility of Fhit-deficient cells in vivo to malignant transformation.