CCR1 and hepatocellular carcinoma: CCL9/CCR1 signaling has been shown to be important for the recruitment of myeloid progenitors to intestinal tumors, leading to enhanced invasion.34TGF-β signaling pathway can activate MDSC to produce CCL9,35Baoyuan Jiedu decoction, a traditional Chinese medicine formula, can inhibit the accumulation of MDSC in premetastatic niche of lung via the downregulated TGF-β/CCL9 pathway in 4T1 tumor-bearing mice.36So, what is the upstream signaling of CCL9 in H22 orthotopic hepatoma mice?