Expression level of CRKL and AXL combined with exon 19 deletion in EGFR and ALK status confer differential prognosis of lung adenocarcinoma subtypes

Abstract

Non-small cell lung cancer (NSCLC) is a lethal cancer-related disease in population. Adenocarcinoma (AC) is subclassified into several subtypes based on the new classification by the International Association for the Study of Lung Cancer, American Thoracic Society and European Respiratory Society in 2011. Correlation between original expression of Crk-like (CRKL) and anaplastic lymphoma receptor tyrosine kinase in diverse histological components of AC and epidermal growth factor receptor (EGFR) or ALK status was evaluated by immunohistochemistry and sequencing in present study. A total of 106 cases, including 83 patients (78.3%) with mixed-type ACs, were assessed in the present study using eligible follow-up data. The ACs consisted of 32 acinar, 12 papillary, 5 mucinous, 11 micropapillary and 46 solid-predominant ACs. In total, 69.8% samples were composed of 2 or 3 histological components, with different expression levels of CRKL and AXL. ACs with EGFR mutation had a higher level of AXL expression compared with ACs without mutation (P=0.019). Multivariate survival analysis showed that AC subtypes and EGFR mutation subtypes were significantly associated with the progression-free survival (PFS) time. Acinar AC was the subtype with the most notable PFS time (30.6 months), which was significantly different from the PFS time of papillary, mucinous, micropapillary and solid-predominant ACs (hazard ratio, 0.4; 95% CI, 0.21-0.75; P=0.005). Among the ACs with exon 19 mutation, the median PFS time (28.8 months) of patients with a lower level of AXL protein expression was increased compared with the PFS time of patients with the L858R mutation and wild-type EGFR (9.1 months and 11 months, respectively; P=0.03), whereas no significant difference in ACs with an increased level of AXL expression. However, AC patients with higher level of CRKL expression had better PFS (28.8 months) than patients with the L858R mutation and wild-type EGFR (9.1 months and 11.3 months, respectively). Exon 19 deletion is an important status that is associated with an improved response to conventional chemotherapy. The identification of EGFR mutations combined with CRKL and AXL status may potentially alter the way that lung AC is treated.

Keywords: ALK rearrangement; AXL; CRKL; EGFR mutation; lung adenocarcinoma.

Figure 1.

IHC staining of CRKL, AXL and ALK fusion protein in lung AC samples. (A and B) Representative acinar and solid predominant AC tissues. CRKL antibodies showed (A) lower expression level with weak cytoplasmic staining in acinar AC and (B) higher level of protein expression in a solid AC (original magnification, ×100). (C and D) AXL immunostaining also showed (C) lower and (D) higher expression level, with weakly and moderately positive reaction in two acinar ACs, respectively (original magnification ×100). (E) ALK rearrangement positive staining by Ventana IHC; brown staining granules full of cytoplasm could be observed (original magnification, ×200). CRKL, Crk-like; AXL, AXL receptor tyrosine kinase; ALK, anaplastic lymphoma receptor tyrosine kinase; AC, adenocarcinoma; IHC, immunohistochemistry.

Figure 2.

PFS comparisons among AC patients with different EGFR mutation types and treated with conventional chemotherapy. (A) PFS comparisons for patients having different histological subtypes. (B) PFS comparisons for patients receiving conventional chemotherapy. (C) PFS comparisons for patients harboring different EGFR status. EGFR, epidermal growth factor receptor; PFS, progression-free survival; AC, adenocarcinoma MicroP AC, micropapillary AC; TXT+CBP, docetaxel and carboplatin; GEM+CBP, gemcitabine and carboplatin; NVB+CBP, tavelbine and carboplatin; Pemetrexed+PDD, pemetrexed and cisplatin; TAX+CBP, Taxol^® and carboplatin.

Figure 3.

PFS comparisons among AC patients with different expression levels of CRKL and AXL protein combined with EGFR status. (A) PFS comparisons for patients with lower level of AXL expression and different EGFR mutation types. (B) PFS comparisons for patients with higher level of AXL expression and different EGFR mutation types. (C) PFS comparisons for patients with lower level of CRKL protein and different EGFR mutation types. (D) PFS comparisons for patients with higher level of CRKL protein and different EGFR mutation types. PFS, progression-free survival; AC, adenocarcinoma; CRKL, Crk-like; AXL, AXL receptor tyrosine kinase; EGFR, epidermal growth factor receptor;