Regulation of DNA Polymerase POLD4 Influences Genomic Instability in Lung Cancer

• Published in: Cancer research (Chicago, Ill.) Vol. 70; no. 21; pp. 8407 - 8416
• Main Authors: QIN MIAO HUANG, TOMIDA, Shuta, TAKAHASHI, Takashi, SUZUKI, Motoshi, MASUDA, Yuji, ARIMA, Chinatsu, KE CAO, KASAHARA, Taka-Aki, OSADA, Hirotaka, YATABE, Yasushi, AKASHI, Tomohiro, KAMIYA, Kenji
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA American Association for Cancer Research 01.11.2010
• Subjects: Antineoplastic agents; Biological and medical sciences; Blotting, Western; Carcinoma, Non-Small-Cell Lung - enzymology; Carcinoma, Non-Small-Cell Lung - genetics; Carcinoma, Non-Small-Cell Lung - pathology; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Chromatin Immunoprecipitation; DNA Breaks, Double-Stranded; DNA Methylation; DNA Polymerase III - antagonists & inhibitors; DNA Polymerase III - genetics; DNA Polymerase III - metabolism; DNA Repair; DNA Replication; Gene Expression Regulation, Neoplastic; Genomic Instability; Humans; Immunoprecipitation; Lung Neoplasms - enzymology; Lung Neoplasms - genetics; Lung Neoplasms - pathology; Medical sciences; Pharmacology. Drug treatments; Pneumology; Protein Subunits; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - genetics; RNA, Small Interfering - pharmacology; Small Cell Lung Carcinoma - enzymology; Small Cell Lung Carcinoma - genetics; Small Cell Lung Carcinoma - pathology; Tumors; Tumors of the respiratory system and mediastinum; Lung disease; Enzyme; Respiratory disease; Transferases; Lung cancer; Genomics; Malignant tumor; Bronchopulmonary; Nucleotidyltransferases; Regulation(control); Genetics; Bronchus disease; Instability; Genome; DNA-directed DNA polymerase; Cancer
• DOI: 10.1158/0008-5472.can-10-0784
• ISSN: 0008-5472

Genomic instability is an important factor in cancer susceptibility, but a mechanistic understanding of how it arises remains unclear. We examined hypothesized contributions of the replicative DNA polymerase δ (pol δ) subunit POLD4 to the generation of genomic instability in lung cancer. In examinations of 158 lung cancers and 5 mixtures of 10 normal lungs, cell cycle- and checkpoint-related genes generally showed mRNA expression increases in cancer, whereas POLD4 showed reduced mRNA in small cell lung cancer (SCLC). A fraction of non-small cell lung cancer patients also showed low expression comparable with that in SCLC, which was associated with poor prognosis. The lung cancer cell line ACC-LC-48 was found to have low POLD4 expression, with higher histone H3K9 methylation and lower acetylation in the POLD4 promoter, as compared with the A549 cell line with high POLD4 expression. In the absence of POLD4, pol δ exhibited impaired in vitro DNA synthesis activity. Augmenting POLD4 expression in cells where it was attenuated altered the sensitivity to the chemical carcinogen 4-nitroquinoline-1-oxide. Conversely, siRNA-mediated reduction of POLD4 in cells with abundant expression resulted in a cell cycle delay, checkpoint activation, and an elevated frequency of chromosomal gap/break formation. Overexpression of an engineered POLD4 carrying silent mutations at the siRNA target site rescued these phenotypes, firmly establishing the role of POLD4 in these effects. Furthermore, POLD4 overexpression reduced intrinsically high induction of γ-H2AX, a well-accepted marker of double-stranded DNA breaks. Together, our findings suggest that reduced expression of POLD4 plays a role in genomic instability in lung cancer.