Comparison of the X-Radiation, Drug and Ultraviolet-Radiation Responses of Clones Isolated from a Human Colorectal Tumor Cell Line

Abstract

We isolated several clones with a wide range of responses to X radiation from an unirradiated human colorectal (HCT 116) tumor cell line. The responses of one of these clones (HCT116-Clone10) and nine other clones to either fractionated or acute (i.e. single, nonfractionated doses) X irradiation in vitro was similar to that of the parental cell line. By contrast, after the same types of treatment, another clone (HCT116-Clone2) manifested a significantly increased survival whereas a third clone (HCT116-CloneK) manifested a significantly decreased survival relative to the parental cell line. This suggested that they were, respectively, a radioresistant and a radiosensitive clone. All three clones (clones 2, 10, K) retained their tumorigenic phenotype and formed tumors in nude mice. G-banding studies demonstrated that they were of human origin and were derived from the same parental cell line. The metaphases of HCT116-Clone2 demonstrated features commonly associated with genomic instability (i.e. mitotic catastrophe including chromosome and chromatid breaks, dicentrics and additional nonclonal markers). Data obtained by quantitative fluorescence in situ hybridization (Q- FISH) analysis failed to demonstrate any apparent correlation between the radiosensitivity and the relative telomere content of these three clones. Interestingly, HCT116-CloneK was the most resistant to several chemotherapeutic drugs (topotecan, camptothecin, etoposide and cisplatin) with diverse mechanisms of action. Also, there were no significant differences in the survivals of the three clones after treatment with UV radiation. Because of the lack of overlap among the relative sensitivities of these clones to X radiation, chemotherapeutic drugs and UV radiation, these clones may be useful models for evaluating the genetic basis of the response of human tumor cells to these treatment agents both in vitro and in vivo.

Death through a tragedy: mitotic catastrophe

“…This may also be true for heterogeneous and genetically instable clinical tumor samples exposed to radiation. [54][55][56] Most experimental facts concerning the biology of MC are based on observations obtained using cells growing in monolayer, and even if these may serve well as models, extrapolation to three-dimensional in vivo structures should be done with great consideration. 57 In fact, specific cell-cell and cell-matrix interactions may be as important as the genomic background for the MC response, although this point of view is frequently neglected.…”

Transcriptomic profiling of radiation-resistant or -sensitive human colorectal cancer cells: Acute effects of a single X-radiation dose

“…This was because these radiationresistant or -sensitive clones were closely related genetically but differed only in their XR-resistance or -sensitivity (9). However, our cDNA microarray results have demonstrated that at least up to 24 h after XR treatment with an acute dose of 4 Gy, which would have killed more than 50% of the cells in all the 3 clones used in our studies (9), there was no significant up-regulation or down-regulation of the majority of known DNA damage sensor/repair, cell cycle, and or apoptosis related genes in either clone when each was individually compared to the control clone with the same radiation response as the parental HCT116 cells. Instead, our results suggested potentially novel genes, or even new pathways, that may or may not interact with the known DNA damage response routes (detection, repair, cell cycle, apoptosis) that can putatively lead to sensitivity or resistance to XR (1).…”

“…Clone2_XRR , HCT116 CloneK_XRS and HCT116 Clone10_control were all isolated at the same time (9). HCT116 Clone2_XRR and HCT116 CloneK_XRS were subsequently characterized as an XR-resistant and XR-sensitive clone (relative to the parental HCT116 cell line), respectively.…”

“…Cells were seeded into a 25-cm 2 flask on day 0 and used for experimentation on day 3 such that, at the time of irradiation, they were in the exponential phase of growth (9). We carefully controlled growth conditions (temperature, pH, nutrient availability) to minimize variations in genetic expression that were unrelated to treatment effects.…”

“…19,200, covering approximately one-third of all human genes). We compared the in vitro transcriptomic profiles of clones derived from a human colorectal tumor cell line that differed significantly in their XR-response phenotypes (9) following treatment with XR. We believe that such an approach would enhance the probability of deciphering the genetic signatures, if any, that were specifically associated with either XR-resistance or -sensitivity.…”