Introduction 1 4 5 6 7 8 9 10 2 2 11 2 2 HSP70 Materials and methods FIR incubator 11 2 Calculation of FIR absorbed per 10-cm tissue culture dish in the FIR incubator 2 −1 −1 −1 −1 −1 −1 −2 −1 2 2 3 2 2 2 Cell lines and cell culture 2 Measurement of cell number and growth 4 3 Histochemistry 2 Microarray studies and data analysis 2 12 P http://www.godatabase.org HSP70A HSP70A HSP70A HSP70A Xba Bam Reverse transcription (RT)-polymerase chain reaction (PCR) 12–18 2  HSP70A HSP70B HSP70C glyceraldehyde-3-phosphate dehydrogenase G3PDH HSPs G3PDH HSPs G3PDH Quantitative real-time RT-PCR data analysis HSP70A α-actin 2+ HSP70A α-actin HSP70A  α-actin α-actin −1/m HSP70 Enzyme-Linked Immuno Sorbent Assay (ELISA) 5 Protein extraction and Western blotting 6 2 3 4 13 Small interfering RNA (siRNA) 1 4 2  2  Table 1 Characterization of Hsp70 (A, B, and C) Gene Location a  mRNA homology to Hsp70A (%) Alternative names GenBank Hsp70A 6p21.3 100 100 HSPA1A, Hsp72, Hsp70-1a M11717 Hsp70B lq23 84 84 HSPA6, Hsp70B X51757 Hsp70C 6p21.3 99 98 HSPA1B, Hsp72, Hsp70-1b M5980 a Statistical analysis t Results FIR irradiation selectively inhibits the growth of specific cancer cell lines 1 Fig. 1 5 P  Microarray analysis and extraction of candidate gene for FIR control 2 2 2 Fig. 2 a b c d n P  HSP70A HSP70A 3 HSP70A HSP70A 3 3 3 Fig. 3 HSP70 a HSP70 HSP70 b c d e  HSP70A 4 4 4 4 Fig. 4 a b c n P  Discussion In the present studies, we showed that FIR suppresses the proliferation of HSC3, Sa3, and A549 cell lines. Two other cell lines, A431 and MCF7, showed almost no growth arrest in response to FIR. The effect of FIR does not seem to be related to the cell type or source, because these three cell lines have different origins: HSC3 is from a tongue squamous cell carcinoma, Sa3 is from a gingival squamous cell carcinoma, and A549 is from a pulmonary adenocarcinoma. FIR was found to cause hypertrophy without apoptosis in all three sensitive cell lines, although there was a slight increase in necrosis in the Sa3 cells by histological observation. In addition, the expression of apoptosis-related genes was unchanged in the FIR-sensitive cells by microarray analysis. Overall, FIR seemed to cause changes in the cytoskeleton, suppress proliferation, and induce some necrosis without apoptosis. These results raise the question of why proliferation of A431 and MCF7 was not suppressed by FIR. Perhaps something in certain cancer cell lines is present for resistance to FIR. We then focused on genes encoding the HSPs, which are well known to participate in the cellular resistance to stress. We found that HSP70 showed the highest correlation with the growth rate of cancer cells affected by FIR in 35 HSP genes on the microarray system. HSP70 HSP70 12 13 14 19 17 20 21 22 23 Conclusion It was found here for the first time the effect on body temperature range by FIR in several cancer cell lines in vitro, which is controlled by endogenous HSP70 to protect cells from FIR-induced growth arrest. This finding suggests that FIR may be a very effective medical treatment for some cancer cell lines that have a low level of HSP70. Furthermore, if the level of HSP70 in any cancer of a patient is measured, the effect of medical treatment by FIR on the cancer may be predicted.