FOXO1 Suppression is a Determinant of Acquired Lapatinib-Resistance in HER2-Positive Gastric Cancer Cells Through MET Upregulation.
OBJECTIVE
Lapatinib is a candidate drug for treatment of trastuzumab-resistant, human epidermal growth factor receptor 2 (HER2)-positive gastric cancer (GC). Unfortunately, lapatinib resistance renders this drug ineffective. The present study investigated the implication of forkhead box O1 (FOXO1) signaling in the acquired lapatinib resistance in HER2-positive GC cells.


METHODS
Lapatinib-resistant GC cell lines (SNU-216 LR2-8) were generatedin vitroby chronic exposure of lapatinib-sensitive, HER2-positive SNU-216 cells to lapatinib. SNU-216 LR cells with FOXO1 overexpression were generated by stable transfection of a constitutively active FOXO1 mutant (FOXO1A3). HER2 and MET in SNU-216 LR cells were downregulated using RNA interference. The sensitivity of GC cells to lapatinib and/or cisplatin was determined by crystal violet assay. In addition, Western blot analysis, luciferase reporter assay and reverse transcription-polymerase chain reaction were performed.


RESULTS
SNU-216 LR cells showed upregulations of HER2 and MET, but downregulation of FOXO1 compared to parental SNU-216 cells. FOXO1 overexpression in SNU-216 LR cells significantly suppressed resistance to lapatinib and/or cisplatin. In addition, FOXO1 negatively controlled HER2 and MET at the transcriptional level and was negatively controlled by these molecules at the post-transcriptional level. A positive crosstalk was shown between HER2 and MET, each of which increased resistance to lapatinib and/or cisplatin.


CONCLUSIONS
FOXO1 serves as an important linker between HER2 and MET signaling pathways through negative crosstalks and is a key regulator of the acquired lapatinib resistance in HER2-positive GC cells. These findings provide a rationale for establishing a novel treatment strategy to overcome lapatinib resistance in a subtype of GC patients.
Tumour Biology, Cancer Research Institute, Seoul National University College of Medicine, Seoul, Korea.
Jinju
J
Park
Tumour Biology, Cancer Research Institute, Seoul National University College of Medicine, Seoul, Korea.
Yiseul
Y
Choi
Department of Forensic Medicine, National Forensic Service Busan Institute, Yangsan, Korea.
Young San
YS
Ko
Department of Pathology, Seoul National University College of Medicine, Seoul, Korea.
Younghoon
Y
Kim
Department of Pathology, Eulji University Hospital, Eulji University School of Medicine, Daejeon, Korea.
Jung-Soo
JS
Pyo
Department of Pathology, Jeju National University Hospital, Jeju, Korea.
Bo Gun
BG
Jang
Department of Pathology, Seoul National University College of Medicine, Seoul, Korea.
Min A
MA
Kim
Department of Molecular Medicine, Inha University College of Medicine, Incheon, Korea.
Jae-Seon
JS
Lee
Department of Pathology, Seoul National University College of Medicine, Seoul, Korea.
Mee Soo
MS
Chang
Ischemic/Hypoxic Disease Institute Medical Research Center, Seoul National University College of Medicine, Seoul, Korea.
Jong-Wan
JW
Park
Tumour Biology, Cancer Research Institute, Seoul National University College of Medicine, Seoul, Korea.|Ischemic/Hypoxic Disease Institute Medical Research Center, Seoul National University College of Medicine, Seoul, Korea.|Department of Anatomy, Seoul National University College of Medicine, Seoul, Korea.
Byung Lan
BL
Lee
D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use*; D019008:Drug Resistance, Neoplasm; D000071161:Forkhead Box Protein O1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006801:Humans; D000077341:Lapatinib; D019859:Proto-Oncogene Proteins c-met / Q000235:genetics / Q000378:metabolism*; D011799:Quinazolines / Q000494:pharmacology*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D013274:Stomach Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D015854:Up-Regulation
D000970:Antineoplastic Agents; D000071161:Forkhead Box Protein O1; D000077341:Lapatinib; D019859:Proto-Oncogene Proteins c-met; D011799:Quinazolines; D018719:Erb-b2 Receptor Tyrosine Kinases; C085126:FOXO1 protein, human; C508053:ERBB2 protein, human; C491743:MET protein, human
Drug resistance; ErbB-2 receptor; Human FOXO1 protein; Human MET protein; Lapatinib; Stomach neoplasms