Molecular effects of Lapatinib in the treatment of HER2 overexpressing oesophago-gastric adenocarcinoma

Abstract

Background: Lapatinib, a dual EGFR and HER2 inhibitor has shown disappointing results in clinical trials of metastatic oesophago-gastric adenocarcinomas (OGAs), and in vitro studies suggest that MET, IGFR, and HER3 confer resistance. This trial applied Lapatinib in the curative neoadjuvant setting and investigated the feasibility and utility of additional endoscopy and biopsy for assessment of resistance mechanisms ex vivo and in vivo.

Methods: Patients with HER2 overexpressing OGA were treated for 10 days with Lapatinib monotherapy, and then in combination with three cycles of Oxaliplatin and Capecitabine before surgery. Endoscopic samples were taken for molecular analysis at: baseline including for ex vivo culture +/- Lapatinib to predict in vivo response, post-Lapatinib monotherapy and at surgery. Immunohistochemistry (IHC) and proteomic analysis was performed to assess cell kinetics and signalling activity.

Results: The trial closed early (n=10) due to an anastomotic leak in two patients for which a causative effect of Lapatinib could not be excluded. The reduction in Phosphorylated-HER2 (P-HER2) and P-EGFR in the ex vivo-treated biopsy demonstrated good correlation with the in vivo response at day 10. Proteomic analysis pre and post-Lapatinib demonstrated target inhibition (P-ERBB2, P-EGFR, P-PI3K, P-AKT, and P-ERK) that persisted until surgery. There was also significant correlation between the activation of MET with the level of P-Erk (P=0.0005) and P-PI3K : T-PI3K (total PI3K) ratio (P=0.0037). There was no significant correlation between the activation status of IGFR and HER3 with downstream signalling molecules.

Conclusions: Additional endoscopy and biopsy sampling for multiple biomarker endpoints was feasible and confirmed in vitro data that MET is likely to be a significant mechanism of Lapatinib resistance in vivo.

Figure 1

Study design where patients undergo a baseline biopsy and ex vivo sample was taken at D0. Patients then received 10 days of Lapatinib monotherapy after which a repeat biopsy and functional imaging was performed. Patients went on to receive three cycles of Oxaliplatin and Capecitabine concurrent with Lapatinib on a 21-day cycle, followed by definitive surgery.

Figure 2

Immunohistochemistry for the phosphorylated species for the RTKs P-HER2, P-EGFR and the downstream molecules P-Erk and P-Akt. Examples of staining performed using the Axio Slide Scanner (Oberkochen, Germany) at 40 × and images at a 35% digital zoom. No 3+ staining was observed for P-Akt.

Figure 3

Phosphorylated:total (P : T) receptor ratios for HER2 (A), EGFR (B), and p95HER2 (C), along with the downstream molecules P-PI3K : T-PI3K ratio (D), P-Akt (E), and P-Erk (F) at baseline, D10 and surgery.

Figure 4

The ratio of phosphorylated to total protein amount representing the activation status of c-met (A), IGFR (B), and HER3 (C), plotted against the activated downstream signalling molecules P-Erk (i), and P-PI3K : T-PI3K (ii) ratio.