However, tumor progression and eventual invasion of the host is also dependent on the host response in terms of inflammation and antitumor immunity.

This host response provides both a tumor-promoting environment and an immune barrier to tumor progression that the tumor needs to neutralize or overcome in order to progress (reviewed in [80-82]). Indeed for colorectal carcinoma and other types of cancer, the presence of adaptive immune cells within the tumor has been shown to be a better predictor of tumor progression and prognosis than traditional or molecular tumor staging [83]. Tumors have been shown Lapatinib mouse not only to originate in inflamed learn more tissues due to infections, but some human tumors develop in sterile chronic inflammation, due to mechanical, chemical, radiation, or other types of injury, or due to genetic pathology. For example, chronic indwelling of urinary catheters has been shown to be associated with bladder carcinoma [84], chronic exposure to asbestosis is associated with lung cancer and mesothelioma (chemical) [85], and secondary pancreatitis resulting from a mutation in the trypsinogen gene has been associated with pancreatic carcinoma

[86]. Inflammation has been proposed to be involved in the promotion of cancer, in part through the production of reactive oxygen and nitrogen species; both species induce the formation of DNA cross-links, single- or double-strand breaks that can drive genomic instability and mutations within oncogenes and tumor suppressor genes [80, 87-89]. In addition, clear experimental evidence indicates

that inflammation provides a tumor-promoting environment in which stromal cells and infiltrating inflammatory hematopoietic cells, such as macrophages, produce growth and angiogenic factors as well as tissue remodeling enzymes [80, 90-94] (Fig. 1). Activation of certain oncogenes, such as RET, Hras and Kras, has been shown to Urease induce, both in the transformed cells as well as in surrounding tissue, an intrinsic inflammation with a secretory pattern; this pattern is reminiscent of that observed in senescent cells, of inflammatory mediators and chemokines that attract inflammatory hematopoietic cells, thus initiating and amplifying the inflammatory response [95-99]. Inflammation also causes infiltration by bone-marrow-derived tumor-associated macrophages and monocyte-derived myeloid cell subsets [100], which perform a critical protumorigenic function in creating the tumor environment by remodeling healthy tissue to accommodate the expanding tumor, increasing angiogenesis and suppressing antitumor T-cell responses [101, 102].