Heat-induced Signal Transduction Pathways Leading to Cell Death and Cell Survival in Cancer Cells

In recent years, cancer therapy research has focused on molecular targets. For efficient hyperthermic cancer therapy, potential targets of interest are molecules which respond to heat and selectively activate signal transduction factors which can inhibit cancer cell proliferation. Signal transduction pathways affected by heat include p53 mediated pathways, JNK (Jun N-terminal kinase) mediated pathways, Akt (protein kinase B) mediated pathways, NBS1 (Nijimegen breakage syndrome 1) mediated pathways, classic MAP (mitogen activated protein) kinase mediated pathways, and p38 MAP kinase mediated pathways. Events such as cell death, cell survival, cell proliferation, and/or cell cycle arrest can be affected by these pathways. To learn more about heat-induced gene and protein expression, cDNA arrays and protein microarrays were used to study cellular responses to heat. This paper briefly reviews interactions of pro- and anti-apoptotic genes and proteins which are induced by heat shock and are components of signal transduction pathways.著作権者：日本ハイパーサーミア学会日本ハイパーサーミア学会及び著作者の許諾を得て登

p53 変異型ヒト口腔がん細胞における高LET 放射線によるp53 非依存Akt 生存シグナルの抑制

Although mutations and deletions in the p53 tumor suppressor gene lead to resistance to low linear energy transfer (LET) radiation, high-LET radiation efficiently induces cell lethality and apoptosis regardless of the p53 gene status in cancer cells. Recently, it has been suggested that the induction of p53-independent apoptosis takes place through the activation of Caspase-9 which results in the cleavage of Caspase-3 and poly (ADP-ribose) polymerase (PARP). This study was designed to examine if high-LET radiation depresses serine/threonine protein kinase B (PKB, also known as Akt) and Akt-related proteins. Human gingival cancer cells (Ca9-22 cells) harboring a mutated p53 (mp53) gene were irradiated with 2 Gy of X-rays or Fe-ion beams. The cellular contents of Akt-related proteins participating in cell survival signaling were analyzed with Western Blotting 1, 2, 3 and 6h after irradiation. Cell cycle distributions after irradiation were assayed with flow cytometric analysis. Akt-related protein levels decreased when cells were irradiated with high-LET radiation. High-LET radiation increased G(2)/M phase arrests and suppressed the progression of the cell cycle much more efficiently when compared to low-LET radiation. These results suggest that high-LET radiation enhances apoptosis through the activation of Caspase-3 and Caspase-9, and suppresses cell growth by suppressing Akt-related signaling, even in mp53 bearing cancer cells.博士（医学）・甲第598号・平成25年3月15日Copyright © 2012 Elsevier Inc. All rights reserve

ATR阻害は非相同末端結合および相同組換え修復と非依存的に5-FUを増感する

The anticancer agent 5-fluorouracil (5-FU) is cytotoxic and often used to treat various cancers. 5-FU is thought to inhibit the enzyme thymidylate synthase, which plays a role in nucleotide synthesis and has been found to induce single- and double-strand DNA breaks. ATR Ser/Thr kinase (ATR) is a principal kinase in the DNA damage response and is activated in response to UV- and chemotherapeutic drug-induced DNA replication stress, but its role in cellular responses to 5-FU is unclear. In this study, we examined the effect of ATR inhibition on 5-FU sensitivity of mammalian cells. Using immunoblotting, we found that 5-FU treatment dose-dependently induced the phosphorylation of ATR at the autophosphorylation site Thr-1989 and thereby activated its kinase. Administration of 5-FU with a specific ATR inhibitor remarkably decreased cell survival, compared with 5-FU treatment combined with other major DNA repair kinase inhibitors. Of note, the ATR inhibition enhanced induction of DNA double-strand breaks and apoptosis in 5-FU-treated cells. Using gene expression analysis, we found that 5-FU induced the activation of the intra-S cell-cycle checkpoint. Cells lacking BRCA2 were sensitive to 5-FU in the presence of ATR inhibitor. Moreover, ATR inhibition enhanced the efficacy of the 5-FU treatment, independently of the nonhomologous end-joining and homologous recombination repair pathways. These findings suggest that ATR could be a potential therapeutic target in 5-FU-based chemotherapy.博士（医学）・甲第791号・令和3年3月15日© 2020 Ito et al. Published under exclusive license by The American Society for Biochemistry and Molecular Biology, Inc.This is an Open Access article under the CC BY license(https://creativecommons.org/licenses/by/4.0/)