Alterations in the Mitochondrial Displacement Loop in Lung Cancers

Makoto Suzuki, Shinichi Toyooka, Kuniharu Miyajima, Toshihiko Iizasa, Takehiko Fujisawa, Nebiyou B. Bekele, Adi F. Gazdar

Research output: Contribution to journalArticlepeer-review

95 Scopus citations

Abstract

Purpose: Alterations of the noncoding displacement (D) loop of mitochondrial DNA are present in many cancers. These alterations include numerical changes in a homopolymeric C tract (PCT) at positions 303-309 and single base substitutions (SBS). We determined the frequency of D-loop alterations in lung cancer cell lines and tumors, and related them to clinicopathologic features. Experimental Design: We sequenced the entire D-loop of 28 lung cancer cell lines [12 small cell lung cancer (SCLC) and 16 non-small cell lung cancer (NSCLC)] and matched B-lymphoblastoid cell lines. In 55 resected NSCLCs and corresponding nonmalignant lungs we determined the length of the PCT. Results: In nonmalignant cell lines and tissues the most frequent PCT repeat number was seven (36 of 83; 43%) with a range of six to nine. Alterations, often multiple, were present in 17 of 28 (61%) of the cell lines, including 8 of 12 SCLC (67%) and 9 of 16 NSCLC (56%) lines. They consisted of SBS in 8 of 28 lines (29%), all of which were homoplasmic, and PCT changes in 14 of 28 (50%) lines, 8 of which were homoplasmic. Of interest, 95% (40 of 42) of the SBS were present within the two hypervariable regions in the D-loop. Because SBS were more frequent if PCT changes were present, only the PCT number was determined in resected samples. PCT changes were present in 11 of 55 (20%) of the NSCLC tumors. Changes were never noted in tumors when the PCT number in the nonmalignant tissue was seven, and only two tumor cell lines had changes when the PCT number in the matched lymphoblastoid cell line was seven. These changes were higher in squamous cell carcinomas (8 of 25; 32%) than in adenocarcinomas (3 of 30; 10%; P = 0.04) and in large tumors (T3 and T4; 7 of 20; 35%) compared with smaller tumors (T1 and T2; 4 of 35; 11%; P = 0.04). Smoking history, gender, age, and stage were not related to frequency of PCT change. Conclusions: Our findings indicate that D-loop alterations are frequent in lung cancers and their cell lines, and that these changes are weakly associated with certain clinical parameters. In tumors PCT changes were only present when the corresponding nonmalignant lung demonstrated a variation from the most common repeat number of seven.

Original languageEnglish (US)
Pages (from-to)5636-5641
Number of pages6
JournalClinical Cancer Research
Volume9
Issue number15
StatePublished - Nov 15 2003

ASJC Scopus subject areas

  • Oncology
  • Cancer Research

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