We recently developed a high-throughput proteomics technology, the Micro-Western arrays (Ciaccio MF, Nature Methods 2010). Micro-Western array is a nano-litter scale array-based Western blotting assay. This method allowed us to measure 96 to 384 different phosphosites on multiple proteins of a set of 6 to 15 different samples simultaneously. We applied this technology in investigating molecular mechanism of anticancer effect of small molecular compound. Colon cancer is the third leading cause of cancer-related death in the world. Previously, we reported that agonists for liver X receptors (LXRs) suppressed the proliferation of several human cancer cell lines. LXRβ and LXRβ are nuclear receptors and are important regulators of cholesterol, fatty acid, and glucose homeostasis. 96-well proliferation assay and colony formation assay showed that three commonly used LXR agonists 22(R)-hydroxycholesterol, T0901317, and GW3965 suppressed proliferation of HT-29 and HCT-116 human colon cancer cells dose-dependently. Flow cytometry analysis indicated that LXR agonists induced G1 cell cycle arrest but not apoptosis in colon cancer cells. We then used gene overexpression and shRNA/siRNA knockdown to verify that LXRβ and LXRβ were directly involved in the growth inhibition caused by LXR agonists. To understand the molecular mechanism, we used gene array and Micro-Western Array with more than 240 phosphorylated antibodies targeting signaling network regulating receptor tyrosine kinases (RTKs), cell cycle, cell stress, and PI3K/Akt to systematically investigate signaling proteins being affected by LXR agonists in multiple time points. With help of bioinformatics modeling, our result revealed a potential mechanism how nuclear receptor LXR regulating cell cycle in human colon cancer cells via EGFR/PI3K/Akt and ABCA1/SREBP-1/LDLR signaling. Effect of LXR agonists treatment with or without chemotherapy agents on HT-29 xenograft model and validation of target proteins for LXR agonists in patients’ tissues are currently ongoing. Our observations suggested that LXR agonists treatment may be a potential adjuvant therapy for colon cancers.
Date:
2012-04
Relation:
Cancer Research. 2012 Apr;72:Abstract number 1276.
