Figure 4

Expressional relevance of l -CaD to 5-FU and radiation response in human colon cancer cell lines. (a) Expression of caldesmon isoforms in 14 human colon cancer cell lines. Unlike in colon cancer tumor, most cell lines tested did not express l-CaD (65 kDa). Moderated immunoreactive signal of l-CaD (65 kDa) was detected only in SNU-C5, CaCo2, HCT-116, SW480 and SW620. (b) Relative poor response of l-CaD (65 kDa) positive cell lines to 5-FU and radiation. Expressional levels of h-CaD (80 kDa) isoforms were correlated neither with 5-FU, radiation nor invasion (data not shown). However, cell lines expressed l-CaD (65 kDa) (SNU-C5, CaCo2, HCT-116, SW480, SW620) showed relatively poor response to 5-FU and radiation compared l-CaD (65 kDa) negative cell lines (SNU-C4, SNU-81, SNU-407, SNU-769A, SNU-769B, DLD-1, LoVo, NCI-H508, NCI-H747). (c) Effect of l-CaD (65 kDa) suppression on 5-FU. Treatment of 5-FU treatment after l-CaD siRNA transfection increased 5-FU susceptibility in HCT-116. However, such artificial suppression of l-CaD (65 kDa) did not alter the response to radiation in HCT-116 (data not shown).