Limits...
Inhibition of mutant EGFR in lung cancer cells triggers SOX2-FOXO6-dependent survival pathways.

Rothenberg SM, Concannon K, Cullen S, Boulay G, Turke AB, Faber AC, Lockerman EL, Rivera MN, Engelman JA, Maheswaran S, Haber DA - Elife (2015)

Bottom Line: Treatment of EGFR-mutant lung cancer with erlotinib results in dramatic tumor regression but it is invariably followed by drug resistance.In characterizing early transcriptional changes following drug treatment of mutant EGFR-addicted cells, we identified the stem cell transcriptional regulator SOX2 as being rapidly and specifically induced, both in vitro and in vivo.Together, these observations point to a physiological feedback mechanism that attenuates oncogene addiction-mediated cell death associated with the withdrawal of growth factor signaling and may therefore contribute to the development of resistance.

View Article: PubMed Central - PubMed

Affiliation: Cancer Center, Massachusetts General Hospital, Harvard Medical School, Charlestown, United States.

ABSTRACT
Treatment of EGFR-mutant lung cancer with erlotinib results in dramatic tumor regression but it is invariably followed by drug resistance. In characterizing early transcriptional changes following drug treatment of mutant EGFR-addicted cells, we identified the stem cell transcriptional regulator SOX2 as being rapidly and specifically induced, both in vitro and in vivo. Suppression of SOX2 sensitizes cells to erlotinib-mediated apoptosis, ultimately decreasing the emergence of acquired resistance, whereas its ectopic expression reduces drug-induced cell death. We show that erlotinib relieves EGFR-dependent suppression of FOXO6, leading to its induction of SOX2, which in turn represses the pro-apoptotic BH3-only genes BIM and BMF. Together, these observations point to a physiological feedback mechanism that attenuates oncogene addiction-mediated cell death associated with the withdrawal of growth factor signaling and may therefore contribute to the development of resistance.

Show MeSH

Related in: MedlinePlus

The highest induction of SOX2 in individually isolated subclones ofEGFR-mutant cells occurs in a subset of cells, as forthe parental cells.(A) Immunofluorescence analysis of colonies formed fromsingle HCC827 cells for DAPI (blue), SOX2 (green), and Ki67 (red).(B) Similar analysis of DAPI (blue) and SOX2 (green) inPC9 cells. For HCC827 cells, because the cloning efficiency is extremelylow (<1%), a single cell suspension of HCC827 cells was plated atlow density and allowed to form discrete colonies. PC9 cells were clonedby limiting dilution, and individual subclones were expanded prior toanalysis.DOI:http://dx.doi.org/10.7554/eLife.06132.019
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4384750&req=5

fig2s5: The highest induction of SOX2 in individually isolated subclones ofEGFR-mutant cells occurs in a subset of cells, as forthe parental cells.(A) Immunofluorescence analysis of colonies formed fromsingle HCC827 cells for DAPI (blue), SOX2 (green), and Ki67 (red).(B) Similar analysis of DAPI (blue) and SOX2 (green) inPC9 cells. For HCC827 cells, because the cloning efficiency is extremelylow (<1%), a single cell suspension of HCC827 cells was plated atlow density and allowed to form discrete colonies. PC9 cells were clonedby limiting dilution, and individual subclones were expanded prior toanalysis.DOI:http://dx.doi.org/10.7554/eLife.06132.019

Mentions: To test whether the heterogeneous induction of SOX2 following EGFR inhibitionrepresents a stochastic event or a heritable property shared by a subset of theparental population, we treated cells sequentially with pulses of erlotinib.Retreatment of cells after a period of recovery produced similar heterogeneity ofSOX2+ cells as the initial treatment, pointing to the absence of enrichmentfor highly inducible cells (Figure 2B andFigure 2—figure supplement 4A). Inaddition, SOX2 could still be induced in cells made resistant to erlotinib, but onlyat the much higher doses of drug required to fully inhibit EGFR in resistant cells(Figure 2—figure supplement 4B).Finally, cloning of 5–6 individual HCC827 and PC9 cells consistently generatedmixed populations, including high level SOX2 inducers together with non-expressingcells, demonstrating that this heterogeneity is likely stochastic, rather thanheritable (Figure 2C and Figure 2—figure supplement 5). Thus, erlotinibtreatment of EGFR-mutant cells results in transient andheterogeneous induction of SOX2, with a stochastic distribution, integrally tied toinhibition of EGFR, in which the cells with the highest expression have a lowproliferative index.


Inhibition of mutant EGFR in lung cancer cells triggers SOX2-FOXO6-dependent survival pathways.

Rothenberg SM, Concannon K, Cullen S, Boulay G, Turke AB, Faber AC, Lockerman EL, Rivera MN, Engelman JA, Maheswaran S, Haber DA - Elife (2015)

The highest induction of SOX2 in individually isolated subclones ofEGFR-mutant cells occurs in a subset of cells, as forthe parental cells.(A) Immunofluorescence analysis of colonies formed fromsingle HCC827 cells for DAPI (blue), SOX2 (green), and Ki67 (red).(B) Similar analysis of DAPI (blue) and SOX2 (green) inPC9 cells. For HCC827 cells, because the cloning efficiency is extremelylow (<1%), a single cell suspension of HCC827 cells was plated atlow density and allowed to form discrete colonies. PC9 cells were clonedby limiting dilution, and individual subclones were expanded prior toanalysis.DOI:http://dx.doi.org/10.7554/eLife.06132.019
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4384750&req=5

fig2s5: The highest induction of SOX2 in individually isolated subclones ofEGFR-mutant cells occurs in a subset of cells, as forthe parental cells.(A) Immunofluorescence analysis of colonies formed fromsingle HCC827 cells for DAPI (blue), SOX2 (green), and Ki67 (red).(B) Similar analysis of DAPI (blue) and SOX2 (green) inPC9 cells. For HCC827 cells, because the cloning efficiency is extremelylow (<1%), a single cell suspension of HCC827 cells was plated atlow density and allowed to form discrete colonies. PC9 cells were clonedby limiting dilution, and individual subclones were expanded prior toanalysis.DOI:http://dx.doi.org/10.7554/eLife.06132.019
Mentions: To test whether the heterogeneous induction of SOX2 following EGFR inhibitionrepresents a stochastic event or a heritable property shared by a subset of theparental population, we treated cells sequentially with pulses of erlotinib.Retreatment of cells after a period of recovery produced similar heterogeneity ofSOX2+ cells as the initial treatment, pointing to the absence of enrichmentfor highly inducible cells (Figure 2B andFigure 2—figure supplement 4A). Inaddition, SOX2 could still be induced in cells made resistant to erlotinib, but onlyat the much higher doses of drug required to fully inhibit EGFR in resistant cells(Figure 2—figure supplement 4B).Finally, cloning of 5–6 individual HCC827 and PC9 cells consistently generatedmixed populations, including high level SOX2 inducers together with non-expressingcells, demonstrating that this heterogeneity is likely stochastic, rather thanheritable (Figure 2C and Figure 2—figure supplement 5). Thus, erlotinibtreatment of EGFR-mutant cells results in transient andheterogeneous induction of SOX2, with a stochastic distribution, integrally tied toinhibition of EGFR, in which the cells with the highest expression have a lowproliferative index.

Bottom Line: Treatment of EGFR-mutant lung cancer with erlotinib results in dramatic tumor regression but it is invariably followed by drug resistance.In characterizing early transcriptional changes following drug treatment of mutant EGFR-addicted cells, we identified the stem cell transcriptional regulator SOX2 as being rapidly and specifically induced, both in vitro and in vivo.Together, these observations point to a physiological feedback mechanism that attenuates oncogene addiction-mediated cell death associated with the withdrawal of growth factor signaling and may therefore contribute to the development of resistance.

View Article: PubMed Central - PubMed

Affiliation: Cancer Center, Massachusetts General Hospital, Harvard Medical School, Charlestown, United States.

ABSTRACT
Treatment of EGFR-mutant lung cancer with erlotinib results in dramatic tumor regression but it is invariably followed by drug resistance. In characterizing early transcriptional changes following drug treatment of mutant EGFR-addicted cells, we identified the stem cell transcriptional regulator SOX2 as being rapidly and specifically induced, both in vitro and in vivo. Suppression of SOX2 sensitizes cells to erlotinib-mediated apoptosis, ultimately decreasing the emergence of acquired resistance, whereas its ectopic expression reduces drug-induced cell death. We show that erlotinib relieves EGFR-dependent suppression of FOXO6, leading to its induction of SOX2, which in turn represses the pro-apoptotic BH3-only genes BIM and BMF. Together, these observations point to a physiological feedback mechanism that attenuates oncogene addiction-mediated cell death associated with the withdrawal of growth factor signaling and may therefore contribute to the development of resistance.

Show MeSH
Related in: MedlinePlus