RNA disruption is associated with response to multiple classes of chemotherapy drugs in tumor cell lines

Narendrula, Rashmi; Mispel-Beyer, Kyle; Guo, Baoqing; Parissenti, Amadeo M.; Pritzker, Laura B.; Pritzker, Ken; Masilamani, Twinkle; Wang, Xiaohui; Lannér, Carita

Significant RNA disruption occurred after 24 h exposure to paclitaxel and docetaxel in A2780 cells and after 48 h in CaOV3 ovarian tumor cell lines treated with docetaxel. RNA disruption was always maximal at the longest incubation time (72 h) (Fig. 1) . Carboplatininduced RNA disruption required a longer exposure time for detection (72 h) and RDI values of carboplatintreated cells were significantly different from untreated cells when a 50 μM drug concentration was applied to both A2780 and CaOV3 cells (Fig. 2) . The difference in exposure time and concentration needed to induce RNA disruption may be due to the different mechanisms of action of the two drugs. Furthermore, the drugs produce slightly different rRNA fragments between the 28S and 18S rRNA bands ( Figs. 1 and 2) , although a common rRNA fragment of slightly greater mobility than the 18S rRNA was generated by both agents. Differing RNA fragmentation patterns were observed by Houge et al. depending upon the apoptosis-inducing agent used and the cell line being investigated. They observed a unique cleavage site in the 28S rRNA in bovine endothelial cells, although the RNA cleavage patterns in different cell types were remarkably similar overall [12] . In yeast, different apoptosis-inducing agents or treatments also generated different patterns of rRNA degradation [16] . In another study by He et al. in murine macrophages, rRNA cleavage was induced by the tricothecene mycotoxin deoxynivalenol. The pattern observed by He et al. contains a similar fragment just below the 18S rRNA and contains three fragments in the region between the 28S and 18S rRNA bandssimilar to patterns observed by Houge et al. [12] . In a study by Nadano et al., two different apoptosis-inducing agents were used in Jurkat and U937 cells to initiate rRNA fragmentation (Fas ligand and TNFα), producing a pattern with a band just below the 18S rRNA but with only one clearly discernable band in the region between the 28S and 18S rRNAs [25] . A very different RNA banding pattern was demonstrated by King et al. in S49 cells treated with several different apoptotic stimuli. No degradation band below the 18S rRNA was observed and all 5 degradation bands were derived from the 5'-end of the 28S rRNA [17] . In our study, the RNA disruption pattern generated by taxane treatment is the same in the A2780 and CaOV3 cells, composed of a major fragment below the 18S rRNA band and two major fragments between the 28S and 18S rRNA bands (Fig. 1) . Carboplatin treatment also generated a fragment just below the 18S rRNA band in both A2780 and CaOV3 cells but appeared to generate multiple fragments in the region between the 28S and 18S rRNA (Fig. 2) . Therefore, ordered RNA disruption appears to occur in different ways depending on the cell type and stimulus, suggesting varying mechanisms or reaction kinetics for RNA disruption in cells, depending upon the cell line and/or the RNA disruption-inducing agent.