Morphoproteomic depiction of constitutively activated mTOR and ERK pathways in adenocarcinoma of the large intestine: A pilot study

Abstract

14580 Background: Preclinical studies have demonstrated a role for the mammalian target of rapamycin (mTOR) pathway in intestinal tumorigenesis. However, the mTOR and its related ERK pathway in human adenocarcinoma of the large intestine (ALI) have been little examined. Methods: To assess morphoproteomic alterations of ALI, tissue materials from three patients with ALI were analyzed in the present study. Antibody probes used included phosphorylated (p)-mTOR (Ser-2448) and one of its downstream effectors, p-p70S6K (Thr-389); bcl-2, which undergoes mTOR-dependent phosphorylative inactivation; and p-extracellular signal-regulated kinase (ERK)1/2 (Thr-202/Tyr-204), a co-activator of p-p70S6K. The intensity of the chromogenic signal and the cellular compartmentalization (plasmalemmal, cytoplasmic, and/or nuclear) were assessed and scored on a scale of 0–3+. Results: Moderate to strong (up to 2+ or 3+) expression of p-mTOR and its substrate, p-p70S6K, and p-ERK1/2 was present in all three cases. We also found plasmalemmal translocation of p-mTOR and nuclear translocation of p-p70S6K and p-ERK1/2, indicating constitutive activation of these protein analytes and their corresponding signal transduction pathways. We did not detect bcl-2 expression in any of these cases. Conclusions: Morphoproteomic analysis reveals constitutive activation of the mTOR and ERK pathways in ALI as evidenced by the collective commonalities of expression of p-mTOR, p-p70S6K, and p- ERK1/2 and the plasmalemmal translocation of p-mTOR and nuclear translocation of p-p70S6K and p-ERK1/2. The absence of bcl-2 expression in this context is noteworthy. These findings coincide with the preclinical data on the efficacy of rapamycin and a rapamycin analogue against colon cancer cell lines and xenograft models. Although preliminary, these observations of morphoproteomic alterations represent the first in primary human ALI specimens according to a review of the literature. The present pilot study offers a starting point for further studies (we are currently conducting a confirmatory study with larger series of cases) and the design of clinical trials using such small molecule inhibitors(e.g. rapamycin, RAD001) in a combinational strategy against ALI. No significant financial relationships to disclose.