Lapatinib resistance in HCT116 cells is mediated by elevated MCL-1 expression and decreased BAK activation and not by ERBB receptor kinase mutation.
We have defined some of the mechanisms by which the kinase inhibitor lapatinib kills HCT116 cells. Lapatinib inhibited radiation-induced activation of ERBB1/2, extracellular signal-regulated kinases 1/2, and AKT, and radiosensitized HCT116 cells. Prolonged incubation of HCT116 cells with lapatinib caused cell killing followed by outgrowth of lapatinib-adapted cells. Adapted cells were resistant to serum starvation-induced cell killing and were cross-resistant to multiple therapeutic drugs. Lapatinib was competent to inhibit basal and epidermal growth factor (EGF)-stimulated ERBB1 phosphorylation in adapted cells. Coexpression of dominant-negative ERBB1 and dominant-negative ERBB2 inhibited basal and EGF-stimulated ERBB1 and ERBB2 phosphorylation in parental and adapted cells. However, in neither parental nor adapted cells did expression of dominant-negative ERBB1 and dominant-negative ERBB2 recapitulate the cell death-promoting effects of lapatinib. Adapted cells had increased expression of MCL-1, decreased expression of BAX, and decreased activation of BAX and BAK. Overexpression of BCL-XL protected parental cells from lapatinib toxicity. Knockdown of MCL-1 expression enhanced lapatinib toxicity in adapted cells that was reverted by knockdown of BAK expression. Inhibition of caspase function modestly reduced lapatinib toxicity in parental cells, whereas knockdown of apoptosis-inducing factor expression suppressed lapatinib toxicity. Thus, in HCT116 cells, lapatinib adaptation can be mediated by altered expression of pro- and antiapoptotic proteins that maintain mitochondrial function.
Department of Biochemistry, Virginia Commonwealth University, Richmond, VA 23298-0035, USA.
Aditi Pandya
AP
Martin
Anna
A
Miller
Luni
L
Emad
Mohammed
M
Rahmani
Teneille
T
Walker
Clint
C
Mitchell
Michael P
MP
Hagan
Margaret A
MA
Park
Adly
A
Yacoub
Paul B
PB
Fisher
Steven
S
Grant
Paul
P
Dent
D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D004354:Drug Screening Assays, Antitumor; D004789:Enzyme Activation / Q000187:drug effects; D066246:ErbB Receptors / Q000235:genetics*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D045325:HCT116 Cells; D006801:Humans; D000077341:Lapatinib; D009154:Mutation / Q000235:genetics*; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D011799:Quinazolines / Q000494:pharmacology*; D034741:RNA, Small Interfering / Q000378:metabolism; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000037:antagonists & inhibitors; D020893:Receptor, ErbB-3 / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000378:metabolism*
D066246:ErbB Receptors; D048049:Extracellular Signal-Regulated MAP Kinases; D000077341:Lapatinib; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2; D011799:Quinazolines; D034741:RNA, Small Interfering; D018719:Erb-b2 Receptor Tyrosine Kinases; D020893:Receptor, ErbB-3; D016159:Tumor Suppressor Protein p53; D050998:bcl-2 Homologous Antagonist-Killer Protein; C512478:EGFR protein, human