Therapeutic resistance: characterization and inactivation by specific antiserum of a putative protein family produced by tumour cells.
A multitherapy resistance (MTR) factor produced by Cloudman S91 mouse melanoma cells rescues a responsive cell line after gamma-irradiation, short wavelength ultraviolet light, mitomycin C, vinblastine and actinomycin D. A similar activity with respect to ionizing radiation is now shown to be produced by human melanoma cells and by both human and mouse breast cancer cells but not by five normal cell lines. In these studies, the factor produced in serum-free conditioned medium (SFCM) by Cloudman S91/I3 cells is further characterized. Its activity in a clonogenic assay using related Cloudman S91/amel cells is destroyed by trypsin but not by DNase and is stable for at least 8 days at a variety of temperatures including 37 degrees C. Molecules greater than 30 kDa from SFCM collected from S91/I3 cells were concentrated and separated by preparative zonal electrophoresis (PZE). Bioactivity was present in both the cathode- and the anode-running fractions. The active acidic (anode) fractions were analysed by preparative isoelectric focusing. Bioactivity was present between pI 3.5 and 4.2. These PZE fractions were also used to immunize two rabbits, both of which produced antiserum that abrogated the bioactivity of SFCM and of the PZE cathode fractions. Antiserum also decreased the survival of irradiated S91/I3 producer cells that do not respond to SFCM but nonetheless must require MTR proteins for the expression of radiation resistance. These studies present a model for the production of rescue factors by non-clonogenic tumour cells that may persist in some tumours for considerable periods of time.
Zhou
S
S
Department of Radiology, New Jersey Medical School, Newark 07103-2714, USA.
Li
W
W
Hill
H Z
HZ
Hill
G J
GJ
Kueppers
F
F
McKenna
W G
WG
Muschel
R J
RJ
Wolansky
L J
LJ
Silva
H C
HC
D026921:Amino Acid Transport Systems, Neutral; D000818:Animals; D016895:Culture Media, Serum-Free; D004307:Dose-Response Relationship, Radiation; D004586:Electrophoresis; D006801:Humans; D007106:Immune Sera; D008545:Melanoma / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry* / Q000187:drug effects / Q000276:immunology / Q000528:radiation effects; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000187:drug effects / Q000276:immunology / Q000528:radiation effects; D051379:Mice; D005810:Multigene Family; D009363:Neoplasm Proteins / Q000276:immunology / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D026921:Amino Acid Transport Systems, Neutral; D016895:Culture Media, Serum-Free; D007106:Immune Sera; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D009363:Neoplasm Proteins