Panels of Markers for Erlotinib and Gefitinib Sensitivity Found in NSCLC Cell Lines

NEW YORK-The drive to findmarkers that will predict which patientswill benefit from erlotinib(Tarceva) and gefitinib (Iressa) inchedforward with studies reported fromtwo groups. Both studies used humannon-small-cell lung cancer (NSCLC)cell lines to identify panels of markersthat not only provide the basis fordevelopment of clinically usefulscreening tests for erlotinib and gefitinibsensitivity, but also open newpossibilities for overcoming resistance.EGFR-IndependentActivationRoman Perez-Soler, MD, of MontefioreMedical Center, New York, andcolleagues reported that in a panel ofnine human NSCLC cell lines, twowere highly sensitive to erlotinib(Tarceva) and both expressed epithelialgrowth factor receptor (EGFR).The other seven cell lines were resistant,but five of them expressed EGFR(abstract 7026).Erlotinib induced G1-S phase arrestin sensitive cells and to some extentin resistant cells. Sensitivity toerlotinib did not correlate with expressionof ErbB family genes, nor wasthere any correlation between drugsensitivity and baseline p-HER1 orepithelial growth factor receptor(EGFR) expression.There were no differences in baselineexpression of P-EGFR betweensensitive and resistant cell lines. Baselineexpression of P-ERK1/2, P-AKT,and P-STAT-3 was undetectable orlow in sensitive cell lines but high inmost resistant cell lines.Erlotinib resistance correlated withhigher baseline expression ofp-MAPK, p-Akt, and p-STAT. Inductionof p-HER1/EGFR and p-AKT byEGF was seen in both sensitive andresistant cells and was blocked byerlotinib in both groups."These data support the hypothesisthat HER1/EGFR-independentbaseline activation of downstream signalingmolecules may define the patientsubpopulation that is less likelyto derive a clinical benefit from erlotinibtherapy," Dr. Perez-Soler said.The investigators analyzed effectsof erlotinib on the cell cycle by flowcytometry. They measured expressionof the activated upstream and downstreamelements of the EGFR pathway(EGFR, ERK1/2, AKT, and STAT-3)at baseline and after stimulation withEGF, determined by western blotanalysis.In the second study, investigatorFred R. Hirsch, MD, of the Universityof Colorado Health Sciences Centerin Denver reported gene array datashowing that E-cadherin signalingplays a central role in determininggefitinib sensitivity. High expressionof E-cadherin correlated with highsensitivity to gefitinib and that highexpression of SIP-1 and ZEB-1 correlatedwith high resistance to gefitinib.Dr. Hirsch and colleagues determinedgefitinib sensitivity in 18NSCLC cell lines. Ten cells lines werestudied using oligonucleotide microarrayanalysis. The researchers usedthree distinct filtration and normalizationnormalizationalgorithms to process the expressiondata and generate a list of 144candidate genes. This approach wascombined with five machine-learningalgorithms to build a test set for predictorgenes. The 16 genes whose expressionwas more than threefolddifferent in sensitive vs resistant cellswere verified by quantitative real-timereverse transcriptase polymerase chainreaction (RT-PCR).The final analysis identified a panelof 13 different genes that were able topredict gefitinib in 9 of 10 cell linesused for validation. "This biomarkerpanel may be of significant value forselecting NSCLC patients for gefitinibtreatment," Dr. Hirsch said.Future Study DirectionAccording to Dr. Hirsch, futuredirections for this research will includeconfirming the predictive valueof E-cadherin, HER3, SIP-1, andZEB-1 expression in a test set of celllines and identifying genes in themicroarray gene set that are controlledby SIP-1 and ZEB-1.Dr. Hirsch told Oncology NewsInternational that early work has alreadyshown that five markers fromthis set predicted gefitinib sensitivityin 9 of 10 cell lines tested. "We will alsocontinue attempts to overcome resistanceby blocking ZEB-1 and SIP-1,"he said.The researchers have attempted unsuccessfullyto do this by using histonedeacetylase inhibitors and will be tryingsRNA constructs next. A prospectivetrial evaluating the relationship ofexpression of SIP-1, ZEB-1, E-cadherin,and HER3 to EGFR mutationsis being planned.