Downregulation of p38 MAPK Activation and Radiation-Sensitive 52 Expression Enhances 5-Fluorouracil and Erlotinib-Induced Cytotoxicity in Human Lung Squamous Cells.

Abstract

INTRODUCTION:

5-Fluorouracil (5-FU) is used to treat various cancers, including non-small-cell lung cancer (NSCLC). It inhibits nucleotide synthesis and induces single- and double-strand DNA breaks. In the homologous recombination pathway, radiation-sensitive 52 (Rad52) plays a crucial role in DNA repair by promoting the annealing of complementary single-stranded DNA and stimulating Rad51 recombinase activity. Erlotinib (Tarceva) is a selective epidermal growth factor receptor tyrosine kinase inhibitor with clinical activity against NSCLC cells. However, whether the combination of 5-FU and erlotinib has synergistic activity against NSCLC cells is unknown.

METHODS:

After the 5-FU and/or erlotinib treatment, the expressions of Rad52 mRNA were determined by quantitative real-time polymerase chain reaction analysis. Protein levels of Rad52 and phospho-p38 MAPK were determined by Western blot analysis. We used specific Rad52 or p38 MAPK small interfering RNA and p38 MAPK inhibitor (SB2023580) to examine the role of p38 MAPK-Rad52 signal in regulating the chemosensitivity of 5-FU and/or erlotinib. Cell viability was assessed by MTS assay and trypan blue exclusion assay.

RESULTS:

In 2 squamous cell carcinoma cell lines, namely, H520 and H1703, 5-FU reduced Rad52 expression in a p38 MAPK inactivation-dependent manner. Enhancement of p38 MAPK activity by transfection with MKK6E (a constitutively active form of MKK6) vector increased the Rad52 protein level and cell survival by 5-FU. However, in human lung bronchioloalveolar cell adenocarcinoma A549 cells, 5-FU reduced Rad52 expression and induced cytotoxicity independent of p38 MAPK. Moreover, 5-FU synergistically enhanced the cytotoxicity and cell growth inhibition of erlotinib in NSCLC cells; these effects were associated with Rad52 downregulation and p38 MAPK inactivation in H520 and H1703 cells.

CONCLUSION:

The results provide a rationale for combining 5-FU and erlotinib in lung cancer treatment.

• Authors: Jen-Chung Ko, Jyh-Cheng Chen, Chia-Li Wei, Li-Ling Liu, Chin-Cheng Chien, I-Hsiang Huang, Jou-Min Hsieh, Chen-Shan Chiang, Pei-Yu Tseng, Hsiang-Hung Cheng, Yong-Cing Tsao, Yun-Wei Lin
• Journal: Pharmacology (Pharmacology) Vol. 106 Issue 11-12 Pg. 623-636 ( 2021) ISSN: 1423-0313 [Electronic] Switzerland
• PMID: 34753130 (Publication Type: Journal Article)
• Copyright: © 2021 S. Karger AG, Basel.

Chemical References

• Antineoplastic Agents
• Rad52 DNA Repair and Recombination Protein
• Erlotinib Hydrochloride
• p38 Mitogen-Activated Protein Kinases
• Fluorouracil

Topics

• Antineoplastic Agents (pharmacology)
• Cell Line, Tumor
• Cell Survival (drug effects)
• Down-Regulation (drug effects)
• Erlotinib Hydrochloride (pharmacology)
• Fluorouracil (pharmacology)
• Humans
• Lung Neoplasms (pathology)
• Neoplasms, Squamous Cell (pathology)
• Rad52 DNA Repair and Recombination Protein (drug effects)
• p38 Mitogen-Activated Protein Kinases (drug effects)