The role of TGF-β1–miR-21–ROS pathway in bystander responses induced by irradiated non-small-cell lung cancer cells

Abstract

Background:Many studies have indicated an important implication of radiation-induced bystander effects (RIBEs) in cancer radiotherapy, but the detailed signalling remains unclear.Methods:The roles of tumour growth factor-beta1 (TGF-β1) and miR-21 in medium-mediated RIBEs in H1299 non-small-cell lung cancer cells were investigated using DNA damage, changes in proliferation and levels of reactive oxygen species (ROS) as end points. SB431542, a specific inhibitor of TGF-β type 1 receptor kinases, was used to inhibit TGF-β1 pathways in irradiated and bystander cells. Exogenous miR-21 regulation was achieved through inhibitor or mimic transfection.Results:Compared with relative sham-radiation-conditioned medium, radiation-conditioned medium (RCM) from irradiated cells 1 h post radiation (1-h RCM) caused an increase in ROS levels and DNA damage in bystander cells, while 18-h RCM induced cell cycle delay and proliferation inhibition. All these effects were eliminated by TGF-βR1 inhibition. One-hour RCM upregulated miR-21 expression in bystander cells, and miR-21 inhibitor abolished bystander oxidative stress and DNA damage. Eighteen-hour RCM downregulated miR-21 of bystander cells, and miR-21 mimic eliminated bystander proliferation inhibition. Furthermore, the dysregulation of miR-21 was attenuated by TGF-βR1 inhibition.Conclusions:The TGF-β1–miR-21–ROS pathway of bystander cells has an important mediating role in RIBEs in H1299 cells.

Radiation quality-dependence of bystander effect in unirradiated fibroblasts is associated with TGF-β1-Smad2 pathway and miR-21 in irradiated keratinocytes

“…Although the study from Dickey et al suggests that instead of a primary signaling factor, the changes in the expression of miRNAs are more likely a manifestation of RIBE32, we and others have demonstrated an important mediating role of miRNAs such as miR-21 and miR-663133334. These results support the hypothesis that bystander effect is epigenetically mediated353637.…”

Advances in targeting the transforming growth factor β1 signaling pathway in lung cancer radiotherapy (Review)

“…An in vitro study demonstrated that the TGFB1-miR-21-ROS signaling pathway in bystander cells was critical for bystander responses to manifest in NSCLC (Fig. 2) (61) demonstrated that when NSCLC cells were irradiated with 5 Gy X-rays, the TGFB1 signaling pathway was activated and the cells released certain signaling molecules, including TGFB1, into the surrounding medium. These signaling molecules diffused to bystander cells and activated the TGFB1-miR-21-ROS signaling pathway in these bystander cells (61).…”

“…2) (61) demonstrated that when NSCLC cells were irradiated with 5 Gy X-rays, the TGFB1 signaling pathway was activated and the cells released certain signaling molecules, including TGFB1, into the surrounding medium. These signaling molecules diffused to bystander cells and activated the TGFB1-miR-21-ROS signaling pathway in these bystander cells (61). A prior study also revealed that TGFB-induced miR-183 silenced tumor-associated natural killer (NK) cells (Fig.…”

Key mechanisms involved in ionizing radiation-induced systemic effects. A current review

“…The signal inducing bystander effects have been shown to include factors such as ROS, 66 cytokine(s), [67][68][69] interleukin(s), 66,70 cyclooxygenase-2 (COX-2), [71][72][73] tumor necrosis factor α (TNFα) 70,74 and transforming growth factor β1 (TGF-β1). 49,73,75 The interaction of that signal with the neighboring or a distant cell can lead to variable types of cellular and sub-cellular damage.…”

“…One approach is the transfer of medium from cultured irradiated cells to non-irradiated cells. 20,44,49,67 This technique allows simultaneously the detection and analysis of secreted RIBE factors in the conditioned medium and the study of their effect on non-irradiated (bystander) cells.…”