Molecular analysis of non-small cell lung cancer identifies subsets with different sensitivity to insulin-like growth factor I receptor inhibition

Abstract

Purpose: This study aimed to identify molecular determinants of sensitivity of non-small cell lung cancer (NSCLC) to anti-insulin-like growth factor receptor (IGF-IR) therapy.

Experimental design: A total of 216 tumor samples were investigated, of which 165 consisted of retrospective analyses of banked tissue and an additional 51 were from patients enrolled in a phase II study of figitumumab, a monoclonal antibody against IGF-IR, in stage IIIb/IV NSCLC. Biomarkers assessed included IGF-IR, epidermal growth factor receptor, IGF-II, IGF-IIR, insulin receptor substrate 1 (IRS-1), IRS-2, vimentin, and E-cadherin. Subcellular localization of IRS-1 and phosphorylation levels of mitogen-activated protein kinase and Akt1 were also analyzed.

Results: IGF-IR was differentially expressed across histologic subtypes (P = 0.04), with highest levels observed in squamous cell tumors. Elevated IGF-IR expression was also observed in a small number of squamous cell tumors responding to chemotherapy combined with figitumumab (P = 0.008). Because no other biomarker/response interaction was observed using classical histologic subtyping, a molecular approach was undertaken to segment NSCLC into mechanism-based subpopulations. Principal component analysis and unsupervised Bayesian clustering identified three NSCLC subsets that resembled the steps of the epithelial to mesenchymal transition: E-cadherin high/IRS-1 low (epithelial-like), E-cadherin intermediate/IRS-1 high (transitional), and E-cadherin low/IRS-1 low (mesenchymal-like). Several markers of the IGF-IR pathway were overexpressed in the transitional subset. Furthermore, a higher response rate to the combination of chemotherapy and figitumumab was observed in transitional tumors (71%) compared with those in the mesenchymal-like subset (32%; P = 0.03). Only one epithelial-like tumor was identified in the phase II study, suggesting that advanced NSCLC has undergone significant dedifferentiation at diagnosis.

Conclusion: NSCLC comprises molecular subsets with differential sensitivity to IGF-IR inhibition.

Figure 1

Cy-5 Fluorescence images (20X) of 2 representative of biomarker stainings of samples from the Yale NSCLC cohort for each indicated tissue marker.

Figure 2

AQUA scores of marker expression by histological subtype in the Yale NSCLC cohort (N=165). The central box represents the values from the lower to upper quartile (25 to 75 percentile). In the box plots, the middle line represents the median. A line extends from the minimum to the maximum value, excluding “outside” and “far out” values which are displayed as separate points. An outside value is defined as a value that is smaller than the lower quartile minus 1.5 times the interquartile range, or larger than the upper quartile plus 1.5 times the interquartile range (inner fences). These values are plotted with a square marker. A far out value is defined as a value that is smaller than the lower quartile minus 3 times the interquartile range, or larger than the upper quartile plus 3 times the interquartile range (outer fences). These values are plotted with a round or triangular marker. The number inside the box indicates the number of patients in the subset.

Figure 3

IGF-IR expression in tumors from patients enrolled in a phase 2 study of chemotherapy given alone (PC) or with figitumumab (PCF) (N=44). A. IGF-IR expression in tumors from patients responding (PR) or not responding (SD/PD) to their respective PC or PCF therapy. B. IGF-IR expression in tumors from patients receiving PCF according to response (PR vs. SD/PD) and histological subtype (AD=adenocarcinoma, LC/NOS=large cell carcinoma and undifferentiated, SQ=squamous cell carcinoma). Box plots were constructed as in Figure 2.

Figure 4

Cy-5 Fluorescence images of representative of IGF-IR expression in tumors of patients enrolled a phase 2 study of chemotherapy given alone (PC) or with figitumumab (PCF). Inserts show cytokeratin (green) and DAPI (blue) fluorescence. A-B panels, patients received PCF. C panels, patients received PC.

Figure 5

AQUA scores of marker expression by molecular subtypes in the Yale (A, N=137) and Phase 2 (B, N=43) NSCLC cohorts. Box plots were constructed as in Figure 2. Abbreviations, M=Mesenchymal-like, T=Transitional.

Figure 5

AQUA scores of marker expression by molecular subtypes in the Yale (A, N=137) and Phase 2 (B, N=43) NSCLC cohorts. Box plots were constructed as in Figure 2. Abbreviations, M=Mesenchymal-like, T=Transitional.