ABSTRACT
Due to their ballistic precision, apoptosis induction by protons could be a strategy to specifically eliminate neoplastic cells. To characterize the cellular and molecular effects of these hadrons, we performed dose-response and time-course experiments by exposing different cell lines (PC3, Ca301D, MCF7) to increasing doses of protons and examining them with FACS, RT-PCR, and electron spin resonance (ESR). Irradiation with a dose of 10 Gy of a 26,7 Mev proton beam altered cell structures such as membranes, caused DNA double strand breaks, and significantly increased intracellular levels of hydroxyl ions, are active oxygen species (ROS). This modified the transcriptome of irradiated cells, activated the mitochondrial (intrinsic) pathway of apoptosis, and resulted in cycle arrest at the G2/M boundary. The number of necrotic cells within the irradiated cell population did not significantly increase with respect to the controls. The effects of irradiation with 20 Gy were qualitatively as well as quantitatively similar, but exposure to 40 Gy caused massive necrosis. Similar experiments with photons demonstrated that they induce apoptosis in a significantly lower number of cells and in a temporally delayed manner. These data advance our knowledge on the cellular and molecular effects of proton irradiation and could be useful for improving current hadrontherapy protocols.
Subject(s)
Apoptosis/radiation effects , Neoplasms/radiotherapy , Proton Therapy , Apoptosis/genetics , Base Sequence , Cell Cycle/radiation effects , Cell Line, Tumor , DNA Damage , DNA Primers/genetics , Electron Spin Resonance Spectroscopy , Female , Flow Cytometry , Humans , Male , Necrosis , Neoplasms/genetics , Neoplasms/metabolism , Neoplasms/pathology , Photons/therapeutic use , RNA, Messenger/genetics , RNA, Neoplasm/genetics , Reactive Oxygen Species/metabolism , Reverse Transcriptase Polymerase Chain ReactionABSTRACT
The ability of lung fibroblasts to modulate the immune response has been evaluated by analyzing the synthesis and release of interleukin (IL)-10 and IL-12 by lipopolysaccharide (LPS)-stimulated peripheral blood monocytes exposed to pulmonary fibroblast conditioned medium (FCM). IL-10 and IL-12 contents and gene expression were markedly modified by treatment with FCM as measured by ELISA (+97.5 +/- 12.8% and -68 +/- 7.3% for IL-10 and IL-12, respectively), immunocytochemistry, and reverse transcriptase-polymerase chain reaction (RT-PCR). These effects appeared to be mediated by prostaglandin E(2) (PGE(2)) as the modified release of both cytokines was reduced by treatment with indomethacin and mimicked by addition of exogenous PGE(2.) As a result of the enhanced production of IL-10, exposure of LPS/interferon (IFN)-gamma-activated monocytes to FCM was also able to reduce the expression of the class II major histocompatibility complex (MHC) molecule, human leukocyte-associated antigen-DR (HLA-DR) (-51.8 +/- 8.7%) and of the costimulatory molecule, CD40 (-53.9 +/- 11.7%). The expression of both molecules was completely restored when monocytes were pretreated with a neutralizing anti-IL-10 monoclonal antibody. The FCM obtained from fibrotic lung fibroblasts was instead less efficacious in potentiating LPS-stimulated IL-10 release and, consequently, in reducing HLA-DR and CD40 expression, suggesting that an impairment of the immune regulation operated by fibroblasts may be involved in the maintenance of chronic pulmonary inflammation.
