Cross-talk between Phospho-STAT3 and PLCγ1 Plays a Critical Role in Colorectal Tumorigenesis

Abstract

Hyper-phosphorylation at the Y705 residue of signal transducer and activator of transcription 3 (STAT3) is implicated in tumorigenesis of leukemia and some solid tumors. However, its role in the development of colorectal cancer (CRC) is not well defined. To rigorously test the impact of this phosphorylation on colorectal tumorigenesis, we engineered a STAT3 Y705F knock-in to interrupt STAT3 activity in HCT116 and RKO CRC cells. These STAT3 Y705F mutant cells fail to respond to cytokine stimulation and grow slower than parental cells. These mutant cells are also greatly diminished in their abilities to form colonies in culture, to exhibit anchorage-independent growth in soft agar, and to grow as xenografts in nude mice. These observations strongly support the premise that STAT3 Y705 phosphorylation is crucial in colorectal tumorigenesis. Although it is generally believed that STAT3 functions as a transcription factor, recent studies indicate that transcription-independent functions of STAT3 also play an important role in tumorigenesis. We show here that wild-type STAT3, but not STAT3 Y705F mutant protein, associates with PLCγ1. PLCγ1 is a central signal transducer of growth factor and cytokine signaling pathways that are involved in tumorigenesis. In STAT3 Y705F mutant CRC cells, PLCγ1 activity is reduced. Moreover, over-expression of a constitutively active form of PLC γ1 rescues the transformation defect of STAT3 Y705F mutant cells. In aggregate, our study identifies previously unknown cross-talk between STAT3 and the PLCγ signaling pathways that may play a critical role in colorectal tumorigenesis.

Lysine-Specific Demethylase 1 (LSD1/KDM1A) Contributes to Colorectal Tumorigenesis via Activation of the Wnt/Β-Catenin Pathway by Down-Regulating Dickkopf-1 (DKK1)

“…Somatic cell gene targeting was performed as described previously [35], [36]. Briefly, an 837 bp fragment from intron 6 to exon 7 of the LSD1 locus was amplified for 25 cycles from genomic DNA as the left homology arm (HA) using the following primers: P1, 5′-GGGAAAGUGGACCTCCTACCTGGCTGAT-3′ and P2, 5′-GGAGACAUTCA TTGTAACTGTCGAGCTGCTG-3′.…”

Gain of Interaction with IRS1 by p110α-Helical Domain Mutants Is Crucial for Their Oncogenic Functions

“…As described in (Zhang et al, 2011), 3 million cells were injected subcutaneously into the flanks of 4 to 6-week-old female athymic nude mice. Tumor volume was measured with electronic calipers, and volumes were calculated as length × width 2 /2.…”

Identification and functional characterization of p130Cas as a substrate of protein tyrosine phosphatase nonreceptor 14

“…Soft agar assays were performed as described (43). Briefly, DLD1 and RKO clones were trypsinized, counted twice using a hemocytometer, and plated at 5000 cells/ml in top plugs consisting of 0.4% SeaPlaque agarose (FMC Bioproducts, Rockland, Maine) and McCoy’s 5A medium.…”