Cathepsin C is a tissue-specific regulator of squamous carcinogenesis.

Serine and cysteine cathepsin (Cts) proteases are an important class of intracellular and pericellular enzymes mediating multiple aspects of tumor development. Emblematic of these is CtsB, reported to play functionally significant roles during pancreatic islet and mammary carcinogenesis. CtsC, on the other hand, while up-regulated during pancreatic islet carcinogenesis, lacks functional significance in mediating neoplastic progression in that organ. Given that protein expression and enzymatic activity of both CtsB and CtsC are increased in numerous tumors, we sought to understand how tissue specificity might factor into their functional significance. Thus, whereas others have reported that CtsB regulates metastasis of mammary carcinomas, we found that development of squamous carcinomas occurs independently of CtsB. In contrast to these findings, our studies found no significant role for CtsC during mammary carcinogenesis but revealed squamous carcinogenesis to be functionally dependent on CtsC. In this context, dermal/stromal fibroblasts and bone marrow-derived cells expressed increased levels of enzymatically active CtsC that regulated the complexity of infiltrating immune cells in neoplastic skin, development of angiogenic vasculature, and overt squamous cell carcinoma growth. These studies highlight the important contribution of tissue/microenvironment context to solid tumor development and indicate that tissue specificity defines functional significance for these two members of the cysteine protease family.

De novo carcinogenesis promoted by chronic inflammation is B lymphocyte dependent.

Chronic inflammation predisposes tissue to cancer development; however, regulatory mechanisms underlying recruitment of innate leukocytes toward developing neoplasms are obscure. We report that genetic elimination of mature T and B lymphocytes in a transgenic mouse model of inflammation-associated de novo epithelial carcinogenesis, e.g., K14-HPV16 mice, limits neoplastic progression to development of epithelial hyperplasias that fail to recruit innate immune cells. Adoptive transfer of B lymphocytes or serum from HPV16 mice into T and B cell-deficient/HPV16 mice restores innate immune cell infiltration into premalignant tissue and reinstates necessary parameters for full malignancy, e.g., chronic inflammation, angiogenic vasculature, hyperproliferative epidermis. These findings support a model in which B lymphocytes are required for establishing chronic inflammatory states that promote de novo carcinogenesis.

TIMP-1 alters susceptibility to carcinogenesis.

Tissue inhibitors of metalloproteinases (TIMPs) are a family of multifunctional proteins known to possess a broad range of biological activities, including inhibition of metalloproteinase activity, regulation of proliferation and apoptosis of a variety of cell types, and, depending on the context, differential regulation of angiogenic and inflammatory responses. Elevated mRNA expression of TIMP family members correlates with malignancy and clinical outcome in many human cancer types; however, a protective role for TIMPs also has been observed in various mouse models of human cancer. In the current study, we found distinct spatial-temporal expression patterns for the mRNA of TIMP family members in a mouse model of epithelial carcinogenesis [i.e., keratin 14-human papillomavirus 16 (K14-HPV16) transgenic mice]. To test the hypothesis that elevated expression of TIMP-1 functionally regulates epithelial carcinogenesis, we introduced a human TIMP-1 transgene into K14-HPV16 transgenic mice and assessed neoplastic progression. Results from these studies suggest that TIMP-1 enhances tumorgenicity by potentiating keratinocyte hyperproliferation and appearance of chromosomal aberrations in premalignant cells, thereby increasing their risk to undergo malignant conversion. In addition, TIMP-1 inhibits tissue gelatinolytic activity in tumor stroma, affects stabilization of collagen fibrils, but does not inhibit malignant conversion of dysplasias into carcinomas or development of metastases. The combined implications of these studies suggest that TIMP-1 is an important contributor to epithelial neoplastic progression and supports the concept that TIMP-1 exerts differential regulation on tissues in a stage-dependent manner.

Early neoplastic progression is complement independent.

Infiltration of leukocytes into premalignant tissue is a common feature of many epithelial neoplasms and is thought to contribute to cancer development. However, the molecular and cellular regulatory mechanisms underlying activation of innate host responses to enhanced neoplastic cell proliferation are largely unknown. Considering the importance of the complement system in regulating inflammation during acute pathologic tissue remodeling, we examined the functional significance of complement component 3 (C3) as a regulator of inflammatory cell infiltration and activation during malignant progression by using a transgenic mouse model of multistage epithelial carcinogenesis, e.g., HPV16 mice. Whereas abundant deposition of C3 is a characteristic feature of premalignant hyperplasias and dysplasias coincident with leukocyte infiltration in neoplastic tissue, genetic elimination of C3 neither affects inflammatory cell recruitment toward neoplastic skin nor impacts responding pathways downstream of inflammatory cell activation, e.g., keratinocyte hyperproliferation or angiogenesis. Taken together, these data suggest that complement-independent pathways are critical for leukocyte recruitment into neoplastic tissue and leukocyte-mediated potentiation of tumorigenesis.

FcRgamma activation regulates inflammation-associated squamous carcinogenesis.

Chronically activated leukocytes recruited to premalignant tissues functionally contribute to cancer development; however, mechanisms underlying pro- versus anti-tumor programming of neoplastic tissues by immune cells remain obscure. Using the K14-HPV16 mouse model of squamous carcinogenesis, we report that B cells and humoral immunity foster cancer development by activating Fcgamma receptors (FcgammaRs) on resident and recruited myeloid cells. Stromal accumulation of autoantibodies in premalignant skin, through their interaction with activating FcgammaRs, regulate recruitment, composition, and bioeffector functions of leukocytes in neoplastic tissue, which in turn promote neoplastic progression and subsequent carcinoma development. These findings support a model in which B cells, humoral immunity, and activating FcgammaRs are required for establishing chronic inflammatory programs that promote de novo carcinogenesis.

Stromal regulation of vessel stability by MMP14 and TGFbeta.

Innate regulatory networks within organs maintain tissue homeostasis and facilitate rapid responses to damage. We identified a novel pathway regulating vessel stability in tissues that involves matrix metalloproteinase 14 (MMP14) and transforming growth factor beta 1 (TGFbeta(1)). Whereas plasma proteins rapidly extravasate out of vasculature in wild-type mice following acute damage, short-term treatment of mice in vivo with a broad-spectrum metalloproteinase inhibitor, neutralizing antibodies to TGFbeta(1), or an activin-like kinase 5 (ALK5) inhibitor significantly enhanced vessel leakage. By contrast, in a mouse model of age-related dermal fibrosis, where MMP14 activity and TGFbeta bioavailability are chronically elevated, or in mice that ectopically express TGFbeta in the epidermis, cutaneous vessels are resistant to acute leakage. Characteristic responses to tissue damage are reinstated if the fibrotic mice are pretreated with metalloproteinase inhibitors or TGFbeta signaling antagonists. Neoplastic tissues, however, are in a constant state of tissue damage and exhibit altered hemodynamics owing to hyperleaky angiogenic vasculature. In two distinct transgenic mouse tumor models, inhibition of ALK5 further enhanced vascular leakage into the interstitium and facilitated increased delivery of high molecular weight compounds into premalignant tissue and tumors. Taken together, these data define a central pathway involving MMP14 and TGFbeta that mediates vessel stability and vascular response to tissue injury. Antagonists of this pathway could be therapeutically exploited to improve the delivery of therapeutics or molecular contrast agents into tissues where chronic damage or neoplastic disease limits their efficient delivery.

Type I collagen is a genetic modifier of matrix metalloproteinase 2 in murine skeletal development.

Recessive inactivating mutations in human matrix metalloproteinase 2 (MMP2, gelatinase A) are associated with syndromes that include abnormal facial appearance, short stature, and severe bone loss. Mmp2(-/-) mice have only mild aspects of these abnormalities, suggesting that MMP2 function is redundant during skeletal development in the mouse. Here, we report that Mmp2(-/-) mice with additional mutations that render type I collagen resistant to collagenase-mediated cleavage to TC(A) and TC(B) fragments (Col1a1(r/r) mice) have severe developmental defects resembling those observed in MMP2-null humans. Composite Mmp2(-/-);Col1a1(r/r) mice were born in expected Mendelian ratios but were half the size of wild-type, Mmp2(-/-), and Col1a1(r/r) mice and failed to thrive. Furthermore, composite Mmp2(-/-);Col1a1(r/r) animals had very abnormal craniofacial features with shorter snouts, bulging skulls, incompletely developed calvarial bones and unclosed cranial sutures. In addition, trabecular bone mass was reduced concomitant with increased numbers of bone-resorbing osteoclasts and osteopenia. In vitro, MMP2 had a unique ability among the collagenolytic MMPs to degrade mutant collagen, offering a possible explanation for the genetic interaction between Mmp2 and Col1a1(r). Thus, because mutations in the type I collagen gene alter the phenotype of mice with null mutations in Mmp2, we conclude that type I collagen is an important modifier gene for Mmp2. Developmental Dynamics 236:1683-1693, 2007. (c) 2007 Wiley-Liss, Inc.