Response of a Spontaneous Murine Tumor to Hyperthermia: Factors Which Modify the Thermal Response in Vivo

• Published in: Radiation research 1980-08, Vol.83 (2), p.312-322
• Main Authors: Urano, Muneyasu, Gerweck, Leo E., Epstein, Roger, Cunningham, Mary, Suit, Herman D.
• Format: Article
• Language: English
• Subjects: Air; Animals; Blood; Breathing; Cancer; Cell Line; Cell Survival; Female; Fibrosarcoma - pathology; Fibrosarcoma - therapy; Hot Temperature - therapeutic use; Hydrogen-Ion Concentration; Hyperthermia; Hypoxia; Lungs; Mice; Neoplasm Transplantation; Sarcoma, Experimental - pathology; Sarcoma, Experimental - therapy; Skin Neoplasms - pathology; Skin Neoplasms - therapy; Space life sciences; Time Factors; Transplantation, Isogeneic; Tumor burden; Tumors
• ISSN: 0033-7587; 1938-5404
• DOI: 10.2307/3575282

Factors which may modify the thermal response of a C3Hf/Sed mouse spontaneous fibrosarcoma were studied. Hyperthermia was given in a constant-temperature water bath by immersing the mouse foot or culture flask at 43.5°C. The pH effect was confirmed in the first experiment. Single-cell suspensions were treated at various pH in vitro and cell survival was determined by lung colony assay in vivo. The slope of the survival curve decreased with decreasing pH level without changing extrapolation numbers. To study the effect of tumor size on the thermal response, tumors of four different sizes were treated in vivo. Tumor growth analysis demonstrated that an increase of the thermal sensitivity was associated with increasing tumor volume. ${\rm TCD}_{50}$, treatment time to achieve a tumor control in half the treated animals, also decreased with increasing tumor volume, i.e., 170, 141, 123, and 111 min for 35-, 100-, 270-, and $800\text{-}{\rm mm}^{3}$ tumors, respectively. Comparative studies on in vivo and in vitro cell survival strongly suggested that the tumor pH decreases with tumor growth. An attempt was made to reduce blood pH by adding 15% CO2 in the respiratory air; this resulted in slight enhancement of the thermal response. These results are discussed.