A switch from stromal to tumor cell expression of stromelysin-1 mRNA associated with the conversion of squamous to spindle carcinomas during mouse skin tumor progression

Both Full-Length and Protease-Cleaved Products of Osteopontin Are Elevated in Infectious Diseases

Circulating full-length osteopontin (FL-OPN) is elevated in plasma from patients with various infectious diseases, such as adult T-cell leukemia, Mycobacterium tuberculosis (TB), hepatitis virus infection, leptospirosis, acquired immune deficiency syndrome (AIDS), AIDS/TB, and coronavirus disease 2019 (COVID-19). Proteolysis of OPN by thrombin, matrix metalloproteases, caspase 8/3, cathepsin D, plasmin, and enterokinase generates various cleaved OPNs with a variety of bioactivities by binding to different target cells. Moreover, OPN is susceptible to gradual proteolysis. During inflammation, one of the cleaved fragments, N-terminal thrombin-cleaved OPN (trOPN or OPN-Arg¹⁶⁸ [OPN-R]), induces dendritic cell (DC) adhesion. Further cleavage by carboxypeptidase B2 or carboxypeptidase N removes Arg¹⁶⁸ from OPN-R to OPN-Leu¹⁶⁷ (OPN-L). Consequently, OPN-L decreases DC adhesion. In particular, the differences in plasma level over time are observed between FL-OPN and its cleaved OPNs during inflammation. We found that the undefined OPN levels (mixture of FL-OPN and cleaved OPN) were elevated in plasma and reflected the pathology of TB and COVID-19 rather than FL-OPN. These infections are associated with elevated levels of various proteases. Inhibition of the cleavage or the activities of cleaved products may improve the outcome of the therapy. Research on the metabolism of OPN is expected to create new therapies against infectious diseases.

Stromal cyclin D1 promotes heterotypic immune signaling and breast cancer growth

The cyclin D1 gene encodes the regulatory subunit of a holoenzyme that drives cell autonomous cell cycle progression and proliferation. Herein we show cyclin D1 abundance is increased >30-fold in the stromal fibroblasts of patients with invasive breast cancer, associated with poor outcome. Cyclin D1 transformed hTERT human fibroblast to a cancer-associated fibroblast phenotype. Stromal fibroblast expression of cyclin D1 (cyclin D1^Stroma) in vivo, enhanced breast epithelial cancer tumor growth, restrained apoptosis, and increased autophagy. Cyclin D1^Stroma had profound effects on the breast tumor microenvironment increasing the recruitment of F4/80⁺ and CD11b⁺ macrophages and increasing angiogenesis. Cyclin D1^Stroma induced secretion of factors that promoted expansion of stem cells (breast stem-like cells, embryonic stem cells and bone marrow derived stem cells). Cyclin D1^Stroma resulted in increased secretion of proinflammatory cytokines (CCL2, CCL7, CCL11, CXCL1, CXCL5, CXCL9, CXCL12), CSF (CSF1, GM-CSF1) and osteopontin (OPN) (30-fold). OPN was induced by cyclin D1 in fibroblasts, breast epithelial cells and in the murine transgenic mammary gland and OPN was sufficient to induce stem cell expansion. These results demonstrate that cyclin D1^Stroma drives tumor microenvironment heterocellular signaling, promoting several key hallmarks of cancer.

The gene expression profiles of canine mammary cancer cells grown with carcinoma-associated fibroblasts (CAFs) as a co-culture in vitro

Background

It is supposed that fibroblasts present in tumour microenvironment increase cancer invasiveness and its ability to metastasize but the mechanisms have not been clearly defined yet. Thus, the current study was designed to assess changes in gene expression in five various cancer cell lines grown as a co-culture with the carcinoma-associated fibroblasts (CAFs) in vitro.

Results

A carcinoma-associated fibroblast cell line was isolated from a canine mammary cancer. Then, a co-culture of cancer cells with the CAFs was established and maintained for 72 hrs. Having sorted the cells, a global gene expression in cancer cells using DNA microarrays was examined. The analysis revealed an up-regulation of 100 genes and a down-regulation of 106 genes in the cancer cells grown as a co-culture with the CAFs in comparison to control conditions. The PANTHER binomial statistics tool was applied to determine statistically over-manifested pathways (p < 0.05). Bulk of the up-regulated genes are involved in the adhesion, the angiogenesis, the epithelial-mesenchymal transition (EMT) and generally take part in the developmental processes. These results were further confirmed using real-time qPCR. Moreover, a wound-healing assay and growth characteristics on Matrigel matrix showed that CAFs increase cancer cell migration and matrix invasion.

Conclusion

The results of the current study showed that the co-culturing of cancer cells and the CAFs caused significant changes to the cancer gene expression. The presence of the CAFs in a microenvironment of cancer cells promotes adhesion, angiogenesis and EMT.

Keratinocyte expression of MMP3 enhances differentiation and prevents tumor establishment

Matrix metalloproteinase (MMP)-3 is induced by multiple cell types in the skin during processes involved in both normal and pathological tissue remodeling. We previously demonstrated that MMP3-null animals have an increased sensitivity to the development of squamous cell carcinoma, suggesting that overall, MMP3 has a protective role in squamous cell carcinoma. However, not all cellular responses affected by a loss of MMP3 are tumor-protective, and tumor expression of MMP3 is co-incident with an invasive tumor phenotype. Transgenic mice were generated with MMP3 targeted to keratinocytes to examine the biological role of tumor-produced MMP3. Overexpression of MMP3 reduced tumor multiplicity in response to chemically induced squamous cell carcinoma. Vascular density was increased with MMP3 overexpression; however, other cellular processes, including tumor growth and leukocyte infiltration, were unaffected. In accordance with the change in tumor multiplicity, SP-1 murine papilloma cell lines that were generated to stably express MMP3 lost the capacity to establish palpable tumors following orthotopic injection into immunocompromised mice. Analysis of epidermal biopsies taken at 1 to 2 weeks postinjection revealed that these MMP3-expressing Sp-1 lines had reduced levels of proliferation and pronounced differentiation. These same cells demonstrated an increased ability to differentiate in vitro, an effect that was inhibited by broad-spectrum MMP and selective MMP3 inhibition. These studies suggest that keratinocyte expression of MMP3 promotes cellular differentiation, impeding tumor establishment during tumorigenesis.

Requirement of MMP-3 in anchorage-independent growth of oral squamous cell carcinomas

BACKGROUND

Matrix metalloproteinase-3 (MMP-3) is expressed in various carcinomas; however, its function is not clearly established. This study was to assess its possible role in oral squamous cell carcinomas (OSCCs).

MATERIALS AND METHODS

Specimens of seven oral pre-malignant lesions (OPMLs) and 92 OSCCs were subjected to MMP-3 detection by RT-PCR and Western blot. Antisense oligodeoxynucleotides (AODNs) of MMP-3 were used to transfect OSCC (OECM-1 and SCC-9) and esophageal carcinoma (CE81T/VGH) cell lines, and their growth was subsequently analyzed by XTT and soft-agar colony assay.

RESULTS

MMP-3 transcript was preferentially expressed in OSCCs (71 of 92, 77%) than in OPMLs (two of seven, 29%; P = 0.012). Both MMP-3 transcript and protein levels were significantly higher in OSCC masses than in neighboring tissues (P < 0.0001 and P = 0.04, respectively). Growth of the three cell lines was not affected, while the colony numbers of OECM-1 and CE81T/VGH were significantly reduced by the transfection of MMP-3 AODNs (P = 0.002 and P = 0.004, respectively). SCC-9 did not form colonies in soft-agar/medium.

CONCLUSIONS

MMP-3 function may be required in most OSCCs, and it may support the anchorage-independent growth of both OSCC and esophageal carcinoma.

Tissue-Specific Consequences of Cyclin D1 Overexpression in Prostate Cancer Progression

The cyclin D1 oncogene encodes the regulatory subunit of a holoenzyme that phosphorylates and inactivates the Rb protein and promotes progression through G(1) to S phase of the cell cycle. Several prostate cancer cell lines and a subset of primary prostate cancer samples have increased cyclin D1 protein expression. However, the relationship between cyclin D1 expression and prostate tumor progression has yet to be clearly characterized. This study examined the effects of manipulating cyclin D1 expression in either human prostatic epithelial or stromal cells using a tissue recombination model. The data showed that overexpression of cyclin D1 in the initiated BPH-1 cell line increased cell proliferation rate but did not elicit tumorigenicity in vivo. However, overexpression of cyclin D1 in normal prostate fibroblasts (NPF) that were subsequently recombined with BPH-1 did induce malignant transformation of the epithelial cells. The present study also showed that recombination of BPH-1 + cyclin D1-overexpressing fibroblasts (NPF(cyclin D1)) resulted in permanent malignant transformation of epithelial cells (BPH-1(NPF-cyclin D1) cells) similar to that seen with carcinoma-associated fibroblasts (CAF). Microarray analysis showed that the expression profiles between CAFs and NPF(cyclin D1) cells were highly concordant including cyclin D1 up-regulation. These data indicated that the tumor-promoting activity of cyclin D1 may be tissue specific.

Matrix metalloproteinase localisation by in situ-RT-PCR in archival human breast biopsy material

Utilising archival human breast cancer biopsy material we examined the stromal/epithelial interactions of several matrix metalloproteinases (MMPs) using in situ-RT-PCR (IS-RT-PCR). In breast cancer, the stromal/epithelial interactions that occur, and the site of production of these proteases, are central to understanding their role in invasive and metastatic processes. We examined MT1-MMP (MMP-14, membrane type-1-MMP), MMP-1 (interstitial collagenase) and MMP-3 (stromelysin-1) for their localisation profile in progressive breast cancer biopsy material (poorly differentiated invasive breast carcinoma (PDIBC), invasive breast carcinomas (IBC) and lymph node metastases (LNM)). Expression of MT1-MMP, MMP-1 and MMP-3 was observed in both the tumour epithelial and surrounding stromal cells in most tissue sections examined. MT1-MMP expression was predominantly localised to the tumour component in the pre-invasive lesions. MMP-1 gene expression was relatively well distributed between both tissue compartments, while MMP-3 demonstrated highest expression levels in the stromal tissue surrounding the epithelial tumour cells. The results demonstrate the ability to distinguish compartmental gene expression profiles using IS-RT-PCR. Further, we suggest a role for MT1-MMP in early tumour progression, expression of MMP-1 during metastasis and focal expression pattern of MMP-3 in areas of expansion. These expression profiles may provide markers for early breast cancer diagnoses and present potential therapeutic targets.

Interpreting epithelial cancer biology in the context of stem cells: tumor properties and therapeutic implications

Over 90% of all human neoplasia is derived from epithelia. Significant progress has been made in the identification of stem cells of many epithelia. In general, epithelial stem cells lack differentiation markers, have superior in vivo and in vitro proliferative potential, form clusters in association with a specialized mesenchymal environment (the 'niche'), are located in well-protected and nourished sites, and are slow-cycling and thus can be experimentally identified as 'label-retaining cells'. Stem cells may divide symmetrically giving rise to two identical stem cell progeny. Any stem cells in the niche, which defines the size of the stem cell pool, may be randomly expelled from the niche due to population pressure (the stochastic model). Alternatively, a stem cell may divide asymmetrically yielding one stem cell and one non-stem cell that is destined to exit from the stem cell niche (asymmetric division model). Stem cells separated from their niche lose their stemness, although such a loss may be reversible, becoming 'transit-amplifying cells' that are rapidly proliferating but have a more limited proliferative potential, and can give rise to terminally differentiated cells. The identification of the stem cell subpopulation in a normal epithelium leads to a better understanding of many previously enigmatic properties of an epithelium including the preferential sites of carcinoma formation, as exemplified by the almost exclusive association of corneal epithelial carcinoma with the limbus, the corneal epithelial stem cell zone. Being long-term residents in an epithelium, stem cells are uniquely susceptible to the accumulation of multiple, oncogenic changes giving rise to tumors. The application of the stem cell concept can explain many important carcinoma features including the clonal origin and heterogeneity of tumors, the occasional formation of tumors from the transit amplifying cells or progenitor cells, the formation of precancerous 'patches' and 'fields', the mesenchymal influence on carcinoma formation and behavior, and the plasticity of tumor cells. While the concept of cancer stem cells is extremely useful and it is generally assumed that such cells are derived from normal stem cells, more work is needed to identify and characterize epithelial cancer stem cells, to address their precise relationship with normal stem cells, to study their markers and their proliferative and differentiation properties and to design new therapies that can overcome their unusual resistance to chemotherapy and other conventional tumor modalities.

A Protective Role for Matrix Metalloproteinase-3 in Squamous Cell Carcinoma

Elevated expression of matrix metalloproteinase-3 (MMP-3/stromelysin-1) is associated with a variety of tumor types, although its in vivo functional role remains unclear. In human and murine squamous cell carcinoma (SCC), MMP-3 is expressed in the stromal compartment at all of the stages of tumor progression and is expressed by the malignant epithelial cells in late-stage, highly invasive tumors. To elucidate whether MMP-3 plays a causal role during SCC, wild-type and MMP-3 null mice were subjected to chemical carcinogenesis procedures by topical application of either the complete carcinogen 1-methyl-3-nitro-1-nitroso-guanidine or two-stage initiation and promotion with 7,12-dimethylbenz[a]anthracene and 12-O-tetradecanoylphorbol-13-acetate. Contrasting with our expectations, tumors originating on MMP-3 null mice had enhanced initial tumor growth rates as compared with control animals, although there was no difference in tumor onset or incidence. This elevated rate in growth was coupled with an elevated proliferative index and a reduced vasculature density but with no significant effect on apoptosis. Tumors from MMP-3 null mice had a prevalence of undifferentiated spindle tumors as compared with controls, which was concomitant with a higher percentage of MMP-3 null mice evidencing surface lung metastases. Tumor progression in MMP-3 null mice was inversely associated with leukocyte infiltration, in which an overall reduction in tumor-associated macrophages and neutrophils was evident. We propose that MMP-3 is expressed as a protective response and plays an important role in host defense during SCC tumorigenesis.

Clinical implications of matrix metalloproteinases

Matrix metalloproteinases (MMPs) are a family of neutral proteinases that are important for normal development, wound healing, and a wide variety of pathological processes, including the spread of metastatic cancer cells, arthritic destruction of joints, atherosclerosis, pulmonary fibrosis, emphysema and neuroinflammation. In the central nervous system (CNS), MMPs have been shown to degrade components of the basal lamina, leading to disruption of the blood brain barrier and to contribute to the neuroinflammatory responses in many neurological diseases. Inhibition of MMPs have been shown to prevent progression of these diseases. Currently, certain MMP inhibitors have entered into clinical trials. A goal to the future should be to design selective synthetic inhibitors of MMPs that have minimum side effects. MMP inhibitors are designed in such a way that these can not only bind at the active site of the proteinases but also to have the characteristics to bind to other sites of MMPs which might be a promising route for therapy. To name a few: catechins, a component isolated from green tea; and Novastal, derived from extracts of shark cartilage are currently in clinical trials for the treatment of MMP-mediated diseases.

Tumor promoter-induced MMP-13 gene expression in a model of initiated epidermis

In mouse epidermis in vivo, the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) increases gene expression of matrix metalloproteinase-13 (MMP-13), an enzyme implicated in carcinogenesis. Here we used a keratinocyte cell line (308) derived from initiated mouse skin to investigate TPA-induced MMP-13 gene expression. Use of a pharmacological inhibitor (U0126) demonstrated that extracellular signal regulated kinase (ERK) plays a major role in TPA-induced MMP-13 gene expression. The 5'-flanking sequences of the MMP-13 gene contain binding sites for activator protein-1 (AP-1) and Runx. Both transcription factor families can be modulated by ERK and have been implicated in MMP-13 gene expression. TPA stimulated ERK-dependent increases in c-Fos protein and the c-Fos content of AP-1 complexes. MMP-13 promoter studies indicated that TPA requires AP-1, but not Runx, to induce MMP-13 gene expression. These studies show that in mouse keratinocytes MMP-13 gene expression can be induced through a Runx-independent pathway that involves the ERK-dependent modulation of AP-1.

Modulation of prostate cancer growth in bone microenvironments

Bone remains one of the major sites, and most lethal host organs, for prostate cancer metastasis. Prostate cell spread and establishment in bone depends on multiple reciprocal modifications of bone stromal and epithelial cancer cell behaviors. This review focuses on recent advances in the characterization of cell-cell and cell-matrix interplay, effects on cell growth, adhesion and invasion, and several therapeutic possibilities for co-targeting prostate cancer cells and bone stroma. We address the topic from three main perspectives: (1) the normal and aging bone stromal environment, (2) the "reactive" bone stromal environment, and (3) the cancerous prostate epithelial cells themselves. First, normal, and especially aging, bones provide uniquely rich and "fertile soil" for roaming cancer cells. The interactions between prostate cancer cells and insoluble extracellular matrices, soluble growth factors, and/or sex steroid hormones trigger bone remodeling, through increased osteoclastogenesis and furthur matrix metalloproteinase activity. Second, after cancer cell arrival and establishment in the bone, host stromal cells respond, becoming "reactive" in a process again involving extracellular matrix remodeling, together with growth factor and steroid receptor signaling this process ultimately enhances cancer cell migration, stromal transdifferentiation, and invasion of the cancer tissues by stromal, inflammatory, and immune-responsive cells. Third, prostate cancer cells also respond to supportive bone microenvironments, where soluble and matrix-associated molecules affect cancer cell growth and gene expression, especially altering cancer cell surface receptor and integrin-mediated cell signaling. We discuss both integrin cell-matrix and gap junctional cell-cell communication between cancer cells and their microenvironments during prostate cancer progression.

Role of the stromal microenvironment in carcinogenesis of the prostate

The topic of this review is the role of stromal-epithelial interactions in normal and malignant prostatic growth. Because cell-cell interactions and androgens play such key roles in the prostate, the goal of this review will be to apply endocrinologic and developmental concepts to the understanding of normal and malignant prostatic growth. Prostatic development is induced by androgens, which act via androgen receptors. Androgens elicit prostatic epithelial growth during fetal and prepubertal periods, and in adulthood androgens act via reciprocal homeostatic stromal-epithelial interactions to maintain functional differentiation and growth quiescence. During carcinogenesis, these reciprocal homeostatic stromal-epithelial interactions are disrupted. In this review, 2 models of prostatic carcinogenesis will be reviewed, both of which emphasize the role of the stromal microenvironment in the carcinogenic process. Hormonal carcinogenesis of the prostate can be elicited by treatment of rats and mice with testosterone plus estradiol (T+E2). Using an immortalized but nontumorigenic human prostatic epithelial cell line (BPH-1), tissue recombinant studies were employed to explore the cellular mechanisms of prostatic carcinogenesis. Accordingly, human BPH-1 prostatic epithelial cells were combined with rat UGM, and the resultant UGM+BPH-1 recombinants were grown in adult male nude mouse hosts. In untreated mouse hosts, UGM+BPH-1 recombinants produced solid branched epithelial cords and ductal structures exhibiting benign growth. In T+E2-treated hosts, UGM+BPH-1 recombinants formed invasive carcinomas. Since BPH-1 cells lack androgen and estrogen receptors, whereas rat UGM expresses both of these receptors, it is proposed that hormonal carcinogenesis is elicited by T+E2 via paracrine mechanisms mediated by the stromal microenvironment. During prostatic carcinogenesis in rats and humans, the periepithelial stroma undergoes progressive loss in smooth muscle with the appearance of carcinoma-associated fibroblasts (CAFs). This abnormal stroma was shown to promote carcinogenesis in genetically abnormal but nontumorigenic epithelial cells. CAF+BPH-1 tissue recombinants grown in male hosts formed carcinomas, whereas benign growth and orderly tissue architecture developed in recombinants composed of normal prostatic stroma+BPH-1. Malignant transformation triggered by CAF was associated with additional genetic alterations and changes in gene expression in the BPH-1 cells. Thus, the stromal microenvironment is a critical determinant of benign versus malignant growth.

Role of stroma in carcinogenesis of the prostate

Prostatic development is induced by androgens acting via mesenchymal-epithelial interactions. Androgens elicit their morphogenetic effects by acting through androgen receptors (ARs) in urogenital sinus mesenchyme (UGM), which induces prostatic epithelial development. In adulthood reciprocal homeostatic stromal-epithelial interactions maintain functional differentiation and growth-quiescence. Testosterone plus estradiol (T+E2) have been shown to induce prostatic carcinogenesis in animal models. Thus, tissue recombinant studies were undertaken to explore the mechanisms of prostatic carcinogenesis in BPH-1 cells in which ARs and estrogen receptors (ERs) are undetectable. For this purpose, BPH-1 cells were combined with UGM, and the UGM+BPH-1 recombinants were grafted to adult male hosts. Solid branched epithelial cords and ductal structures formed in untreated UGM+BPH-1 recombinants. Growth was modest, and tumors did not develop. UGM+BPH-1 recombinants treated with T+E2 formed invasive carcinomas. BPH-1 cells lack ARs and ERs, whereas rat UGM expresses both of these receptors. These data show that immortalized nontumorigenic human prostatic epithelial cells can undergo hormonal carcinogenesis in response to T+E2 stimulation via paracrine mechanisms and demonstrate that the stromal environment plays an important role in mediating hormonal carcinogenesis. During prostatic carcinogenesis the stroma undergoes progressive loss of smooth muscle with the appearance of carcinoma-associated fibroblasts (CAF). This altered stroma was tested for its ability to promote carcinogenesis of nontumorigenic but immortalized human prostatic epithelial cells (BPH-1). CAF+BPH-1 tissue recombinants formed large carcinomas. In contrast, recombinants composed of normal prostatic stroma+BPH-1 cells exhibited minimal growth. This stroma-induced malignant transformation was associated with additional genetic alterations and changes in gene expression. Thus, alteration in the stromal microenvironment was sufficient to promote malignant transformation of human prostatic epithelial cells.

Keratinocyte stimulation of matrix metalloproteinase-1 production and proliferation in fibroblasts: regulation through mitogen-activated protein kinase signalling events

Incubation of human dermal fibroblasts in keratinocyte-conditioned culture medium led to a 5.7-fold increase in the level of matrix metalloproteinase-1. Virtually all of the matrix metalloproteinase-1 - inducing activity could be related to agonists acting through members of the epidermal growth factor receptor family or to agonists acting through the interleukin-1 receptor. The same keratinocyte-conditioned medium also induced a modest increase in fibroblast proliferation (approximately 1.8-fold). Growth-stimulating activity could be attributed to epidermal growth factor receptor (but not interleukin-1 receptor) function. In fibroblasts exposed to keratinocyte-conditioned medium, mitogen-activated protein kinase signalling through both the extracellular signal-related kinase pathway and p38 pathway occurred. When recombinant epidermal growth factor or recombinant interleukin-1beta were used as a control, they induced mitogen-activated protein kinase signalling consistent with the combined effects of epidermal growth factor receptor - specific and interleukin-1 receptor - specific agonists in keratinocyte-conditioned medium. Recombinant epidermal growth factor stimulated both matrix metalloproteinase-1 induction and proliferation while recombinant interleukin-1beta stimulated matrix metalloproteinase-1 elaboration but not fibroblast growth. An inhibitor of extracellular signal-related kinase pathway signalling (U0126) blocked induction of matrix metalloproteinase-1 production induced by keratinocyte-conditioned medium (as well as by epidermal growth factor or interleukin-1beta), and also inhibited proliferation. A p38 signalling inhibitor (SB203580) blocked matrix metalloproteinase-1 elaboration induced by keratinocyte-conditioned medium or interleukin-1beta, but did not inhibit matrix metalloproteinase-1 elaboration or cell growth induced by epidermal growth factor. These data indicate that keratinocyte-fibroblast interactions are mediated by multiple stimulating agents acting on specific receptors to induce signalling through different mitogen-activated protein kinase pathways leading to altered expression of key biological functions.

Stromelysin-1 activation correlates with invasiveness in squamous cell carcinoma

The expression of selected metalloproteinases and tissue inhibitors of metalloproteinases (TIMP) was examined in three squamous cell carcinoma (SCC) cell lines (FaDu, SiHa, A431) and a keratinocyte cell line (HaCaT) to determine which metalloproteinases function in SCC invasiveness. A Matrigel invasion assay was used to assess invasiveness of the cell lines. Only the FaDu cell line showed invasiveness in this assay, and invasion of Matrigel by FaDu cells was inhibited by treatment with the metalloproteinase inhibitor, batimastat. No correlation was found between mRNA expression for matrilysin, stromelysins 1-3, TIMP-1, or TIMP-3 and secretion of these proteins, indicating that the extracellular activity of these molecules is regulated post-transcriptionally. The SCC cell lines differed from the HaCaT line in that matrilysin and TIMP-1 proteins were detected in conditioned medium from all SCC cell lines, but not in medium from HaCaT cells. Only the invasive cell line, FaDu, released active stromelysin-1 into the culture medium. These results indicate that while matrilysin contributes to the invasive phenotype, activation of stromelysin-1 is a key regulatory step for invasiveness in SCC cells.

Identification and characterization of genes involved in the carcinogenesis of human squamous cell cervical carcinoma

We utilized RT-PCR differential display and cDNA microarrays to identify cellular genes involved in the multi-step carcinogenesis of squamous cell cervical carcinoma. Thirty-eight cervical cancer patients in various stages of the disease and 5 non-cervical cancer patients were studied. Twenty-five cDNA clones were identified and these were subsequently demonstrated to be consistently over-expressed in squamous cell cervical carcinoma biopsies of various FIGO stages. To further evaluate the possible role that these genes may play in the progression of disease, we performed Northern blot analysis and RNA-RNA in situ hybridization studies using cervical cancer biopsies of various FIGO stages. Of particular interest are the 2 clones G32C4B and G30CC that have been identified to be the NADH dehydrogenase 4 gene and the gene that encodes ribosomal protein S12 respectively when compared to sequences available in the GenBank database. Increased expression of these 2 genes were detected in the matched normal tissues collected together with the late FIGO stages of cervical cancer biopsies. In comparison, upregulation of these 2 genes was not detected in cervical squamous epithelium collected from patients admitted for surgery for non-malignant conditions, suggesting that expression of these 2 genes may have altered in the adjacent histopathologically "normal" cervical squamous epithelial tissue from cervical cancer patients. The ribosomal protein S12 and the NADH dehydrogenase 4 genes may therefore be potentially useful as early pre-transformation diagnostic markers for human cervical cancer.

Identification of molecular markers for the early detection of human squamous cell carcinoma of the uterine cervix

To identify novel cellular genes that could potentially act as predictive molecular markers for human cervical cancer, we employed RT--PCR differential display, reverse Northern and Northern blot analysis to compare the gene expression profiles between squamous cell carcinoma biopsies and adjacent histo-pathological normal epithelium tissues. Twenty-eight cDNA clones were isolated that were demonstrated to be consistently over-expressed in squamous cell cervical cancer biopsies of FIGO stages 1B to 3B. Most importantly, it was observed that, in addition to their over-expression in cancer lesions, some of these genes are upregulated in the presumably histo-pathological normal adjacent tissues. Of particular interest is clone G30CC that has been identified to be the gene that encodes S12 ribosomal protein. When employed for RNA--RNA in situ hybridization experiments, expression of G30CC could be detected in the immature basal epithelial cells of histo-pathological normal tissues collected from cervical cancer patients of early FIGO stages. In comparison, the expression of G30CC was not detected in cervical tissues collected from patients admitted for surgery of non-malignant conditions. These results allow the distinct possibility of employing the ribosomal protein S12 gene as an early molecular diagnostic identifier for the screening of human cervical cancer and a potential target employed for cancer gene therapy trials.

Putting tumours in context

The interactions between cancer cells and their micro- and macroenvironment create a context that promotes tumour growth and protects it from immune attack. The functional association of cancer cells with their surrounding tissues forms a new 'organ' that changes as malignancy progresses. Investigation of this process might provide new insights into the mechanisms of tumorigenesis and could also lead to new therapeutic targets.

Phenotypic alterations in Caki-1 cells as a consequence of TIMP-1 overexpression

Maintenance of the extracellular matrix (ECM) is important for tissue integrity and cellular physiology. Normal ECM turnover is regulated by a balance between matrix metalloproteinases and their inhibitors, the tissue inhibitors of metalloproteinases (TIMPs). In metastasis, this balance favours increased ECM degradation. The objective of this study was to determine the effects of TIMP-1 overexpression on the metastatic process. To this end, we stably transfected a renal carcinoma cell line, Caki-1, with TIMP-1, using a pRc/CMV expression plasmid and LIPOFECTAMINE transfection reagent. The resultant clones displayed increased adhesion on the ECM substratum, including collagen type IV and laminin, and altered invasive capacity through fibronectin and Matrigel, dependent upon the level of TIMP-1 expression. These changes were not due to altered integrin expression, as assessed by flow cytometry. As well as protease inhibitory activity, TIMPs can influence cell proliferation and cell survival. The TIMP-1 clones displayed no changes in proliferation under normal growth conditions, compared with Caki-1 cells. However, under reduced serum conditions, the TIMP-1 clones had a greater percentage of cells in both S (P<0.05) and G(2)/M (P<0.005) phases and less cells in G(0)/G(1) (P<0.001) of the cell cycle than Caki-1 cells. The results confirm a dual role for TIMP-1 in invasion and metastasis, and provide further clues behind the molecular mechanisms in these processes.

Loss of JunB activity enhances stromelysin 1 expression in a model of the epithelial-to-mesenchymal transition of mouse skin tumors

Chemical carcinogenesis in mouse skin has been useful in delineating the molecular events that underlie squamous cell carcinoma progression. A late event in this progression, the epithelial-to-mesenchymal transition (EMT), is characterized by the loss of epithelial markers and the presence of mesenchymal markers. One mesenchymal marker associated with this transition is the matrix metalloproteinase stromelysin 1 (Str-1). To examine the molecular mechanisms regulating the expression of Str-1 during the EMT, genetically related mouse skin tumor cell lines representing the epithelial (B9(SQ)) and mesenchymal (A5(SP)) phenotypes were studied. As expected, B9(SQ) cells did not make Str-1, while A5(SP) cells did. B9(SQ)-A5(SP) somatic hybrids did not make Str-1, suggesting that a critical regulatory factor was a B9(SQ)-specific repressor. Str-1 promoter analysis revealed that a canonical AP-1 site was sufficient to maintain differential reporter gene activity. This result correlated with the observed loss of binding of the transcriptionally inactive JunB-Fra-2 AP-1 complex from B9(SQ) cells, being replaced primarily by the more active JunD-Fra-2 complex in A5(SP) cells. The higher level of JunB binding to both DNA and Fra-2 correlated with its hyperphosphorylation by Jun N-terminal kinase, an activity that was significantly higher in B9(SQ) cells. In the somatic hybrids, JunB gene expression was highly upregulated, a condition that also was sufficient to repress the expression of the endogenous Str-1 gene in A5(SP) cells. These data suggested that alterations in JunB activity, by changes in either phosphorylation or gene expression, contributed to the phenotypic differences that occur in this model of the EMT.

Role of matrix metalloproteinase-9 in progression of mouse skin carcinogenesis

Invasion of malignant tumor cells is required for the formation of metastatic colonies. Uncontrolled expression of matrix metalloproteinase (MMP)-2 and MMP-9 is a critical part of the invasive potential of tumor cells and is affected by the balance between the enzymes and the inhibitors secreted by the cell. Here we analyzed the expression and activity of the two gelatinases (MMP-2 and MMP-9) as well as the expression levels of the tissue inhibitor of metalloproteinase (TIMP2)-, in different stages of carcinogenesis using mouse skin cell lines derived from tumors induced by chemical mutagens. Our results suggested that the expression of MMP-9 was implicated in the progression to spindle cell carcinomas in mouse keratinocytes. MMP-2 levels remained steady in all cell lines, whereas levels of TIMP-2 were increased in normal and spindle cells. The AP-1 DNA binding and transcriptional activity on the MMP-9 promoter were increased in the malignant cell lines, indicating the requirement of this binding site for its activation. The results of this study clearly suggested the important role of MMP-9, but not of MMP-2, in the metastatic properties of mouse keratinocytes.

Osteopontin, a novel substrate for matrix metalloproteinase-3 (stromelysin-1) and matrix metalloproteinase-7 (matrilysin)

Osteopontin (OPN) is a secreted phosphoprotein shown to function in wound healing, inflammation, and tumor progression. Expression of OPN is often co-localized with members of the matrix metalloproteinase (MMP) family. We report that OPN is a novel substrate for two MMPs, MMP-3 (stromelysin-1) and MMP-7 (matrilysin). Three cleavage sites were identified for MMP-3 in human OPN, and two of those sites were also cleaved by MMP-7. These include hydrolysis of the human Gly166-Leu167, Ala201-Tyr202 (MMP-3 only), and Asp210-Leu211 peptide bonds. Only the N-terminal Gly-Leu cleavage site is conserved in rat OPN (Gly151-Leu152). These sites are distinct from previously reported cleavage sites in OPN for the proteases thrombin or enterokinase. We found evidence for the predicted MMP cleavage fragments of OPN in vitro in tumor cell lines, and in vivo in remodeling tissues such as the postpartum uterus, where OPN and MMPs are co-expressed. Furthermore, cleavage of OPN by MMP-3 or MMP-7 potentiated the function of OPN as an adhesive and migratory stimulus in vitro through cell surface integrins. We predict that interaction of MMPs with OPN at tumor and wound healing sites in vivo may be a mechanism of regulation of OPN bioactivity.

The matrix metalloproteinase stromelysin-1 acts as a natural mammary tumor promoter

Extracellular matrix-degrading matrix metalloproteinases (MMPs) are invariably upregulated in epithelial cancers and are key agonists in angiogenesis, invasion and metastasis. Yet most MMPs are secreted not by the cancer cells themselves, but by stromal cells within and around the tumor mass. Because the stromal environment can influence tumor formation, and because MMPs can alter this environment, MMPs may also contribute to the initial stages of cancer development. Several recent studies in MMP-overexpressing and MMP-deficient mice support this possibility, but have required carcinogens or pre-existing oncogenic mutations to initiate tumorigenesis. Here we review the spontaneous development of premalignant and malignant lesions in the mammary glands of transgenic mice that express an autoactivating form of MMP-3/stromelysin-1 under the control of the whey acidic protein gene promoter. These changes were absent in nontransgenic littermates and were quenched by co-expression of a human tissue inhibitor of metalloproteinases-1 (TIMP-1) transgene. Thus by altering the cellular microenvironment, stromelysin-1 can act as a natural tumor promoter and enhance cancer susceptibility.

Matrix metalloproteinase-3-dependent generation of a macrophage chemoattractant in a model of herniated disc resorption

Herniated disc (HD) is a common health problem that is resolved by surgery unless spontaneous resorption occurs. HD tissue contains abundant macrophage infiltration and high levels of matrix metalloproteinases (MMPs) MMP-3 and MMP-7. We developed a model system in which disc tissue or isolated chondrocytes from wild-type or MMP-null mice were cocultured with peritoneal macrophages and used this system to investigate the role of MMPs and chondrocyte/macrophage interactions in disc resorption. We observed a marked enhancement of MMP-3 protein and mRNA in chondrocytes after exposure to macrophages. Chondrocytic MMP-3, but not MMP-7, was required for disc resorption, as determined by assaying for a reduction in wet weight and proteoglycan content after 3 days of coculture. Surprisingly, chondrocyte MMP-3 was required for the generation of a macrophage chemoattractant and the subsequent infiltration of the disc tissue by proteolytically active macrophages. We conclude that macrophage induction of chondrocyte MMP-3 plays a major role in disc resorption by mechanisms that include the generation of a bioactive macrophage chemoattractant.

Cancer biology: extracellular proteinases in malignancy

Secreted, matrix-degrading proteinases have been viewed as contributing to tumor metastasis. A recent study indicates that the gene for one of these enzymes, the matrix metalloproteinase stromelysin-1, can actually cause cancer when expressed in transgenic mice.

'Proteolytic switching': opposite patterns of regulation of gelatinase B and its inhibitor TIMP-1 during human melanoma progression and consequences of gelatinase B overexpression

Although it is generally accepted that proteolytic degradation is an important mechanism used by malignant cells in the process of metastasis, comparatively little is known about the regulation of molecules responsible for proteolysis and how they become de-regulated during human tumour progression. Using a genetically related pair of human melanoma cell lines, derived from the same patient at different stages of disease, we analysed differences in the cytokine-mediated regulation of gelatinase B (MMP-9), an enzyme thought to play an important role in cellular invasiveness, and TIMP-1, a physiological inhibitor of this enzyme. Whereas the advanced stage (i.e. metastatic) partner of this pair (WM 239) could produce gelatinase B upon induction with interleukin (IL)-1beta or tumour necrosis factor alpha (TNF-alpha), the early stage (i.e. primary) partner (WM 115) could not. In sharp contrast, we found that TIMP-1 displayed an opposite pattern of induction in these cell lines. Specifically, the early stage cell line, WM 115, demonstrated a marked increase in the production of TIMP-1 when treated with IL-1beta or TNF-alpha whereas the advanced cell line, WM 239, showed no such increase. Treatment with the DNA demethylating agent, 2-deoxy-5-azacytidine, resulted in a marked up-regulation of both gelatinase B and TIMP-1 in both cell lines. It was further found that constitutive overexpression of gelatinase B in WM 239 cells and an additional melanoma cell line (MeWo), derived from a metastatic lesion, was able to greatly enhance lung colonization in an experimental metastasis assay while we did not observe differences in tumorigenicity. From these results we conclude that an altered responsiveness of gelatinase B and TIMP-1 to induction by similar agents is associated with disease progression in human melanoma and that this altered responsiveness can have consequences to the aggressive nature of the disease.

Transforming growth factor beta 1 induces squamous carcinoma cell variants with increased metastatic abilities and a disorganized cytoskeleton

Previous studies indicated that mouse transformed keratinocytes undergo an epithelial-fibroblastic conversion when cultured in the presence of TGF-beta1. This conversion is associated in vivo with a squamous-spindle carcinoma transition. We derived epithelioid (A6, FPA6) and spindle (B5) clonal cell variants from a squamous carcinoma cell line (PDV) after treatment with TGF-beta1. FPA6 cells were isolated from the ascites fluid of an A6-tumor-bearing mouse. FPA6 and A6 cell lines produced in nude mice mixed carcinomas with a squamous and poorly differentiated component. Both cell lines coexpressed keratins and vimentin and synthesized E-cadherin protein, although FPA6 cells cultured at early passages (FPA6-ep) had reduced levels of E-cadherin mRNA and increased synthesis of keratin K8, a marker of malignant progression. Immunofluorescence analysis revealed that FPA6-ep cells exhibited a disorganized cytoskeleton with keratins forming focal juxtanuclear aggregates and loss of F-actin stress fibers and cortical bundles, and E-cadherin was localized in the cytoplasm out of cell-cell contact areas. Sporadic cells in A6 and PDV cultures also presented those anomalous keratin structures, suggesting that FPA6 cells originated from a subpopulation of A6 tumor cells that metastasized into the peritoneal cavity. The analysis of the spontaneous and experimental metastatic potentials of the cell lines showed that epithelioid and fibroblastic cell variants had acquired metastatic abilities compared to PDV which was nonmetastatic. The FPA6-ep cell line exhibited a highly aggressive behavior, killing the animals at about 17 days after intravenous injection of the cells into athymic mice. The phenotype of FPA6-ep cells was unstable and reverted at later passages in which the normal organization of keratin and F-actin in filaments and the localization of E-cadherin at cell-cell contacts were restored. This phenotypic reversion occurred concomitantly with a reduction of the experimental metastatic potential of FPA6 cells.

The significance of matrix metalloproteinases during early stages of tumor progression

Matrix metalloproteinases (MMPs) orchestrate tissue remodeling and play diverse roles during organ development. They are produced excessively during the course of various pathological conditions, including solid tumors. An important function of MMPs during tumor progression is to provide the proteolytic activity that is necessary both for tumor cells to invade extracellular matrix (ECM) and for neovascularization of tumor tissue by endothelial cells. Recently, independent studies in transgenic animals suggest that MMPs may, in addition, promote very early stages of tumor progression. To investigate this possibility further, we have analyzed the consequences of MMP overexpression in functionally normal and nontumorigenic mouse mammary epithelial cells in culture. Our observations demonstrate that the MMP stromelysin-1 (SL-1) triggers an epigenetic molecular program in mammary epithelial cells that results in a number of phenotypic alterations that eventually culminate in the generation of a malignant tumor-cell phenotype.

MT1-MMP and MMP-2 mRNA expression in human ovarian tumors: possible implications for the role of desmoplastic fibroblasts

Expression of activated MMP-2 (72 kDa type IV collagenase) is highly associated with the malignant phenotype in adenocarcinomas, but predominant expression of the mRNA appears to be in stromal cells. MT1-MMP (membrane type 1-matrix metalloproteinase) is implicated in tumor-epithelial cell surface activation of latent pro-MMP-2, indicating a mechanism for tumor-stromal interaction in invasion. We determined the relative mRNA distribution of these MMPs in human ovarian tumors with a view to analyzing potential variations in the epithelial-mesenchymal interactions dictating ovarian tumor cell spread. In situ hybridization using 35S-labeled riboprobes was used to analyze 33 human ovarian tumors and mouse xenografts of human ovarian (DOV 13, SKOV3) and breast (MCF 7) tumor cell lines known to express MT1-MMP and MMP-2. MMP-2 mRNA was expressed in 31 of 33 and MT1-MMP mRNA was expressed in 29 of 33 tumor cases. MMP-2 mRNA was predominantly expressed in desmoplastic fibroblasts and in the subepithelial stroma. MT1-MMP mRNA showed some colocalization with MMP-2 in stromal cells. Neoplastic epithelial cell labeling for MT1-MMP mRNA was present in borderline and malignant tumors but not in benign tumors, and was invariably less than stromal labeling. Xenografts of DOV 13, SKOV 3, and MCF 7 cells showed some stromal localization of MMP-2 mRNA and weak labeling of DOV 13 cells. There was variable labeling for MT1-MMP mRNA in the neoplastic cells only. The colocalization of MT1-MMP and MMP-2 mRNAs in ovarian carcinoma stroma supports the view that MT1-MMP is closely associated with MMP-2 expression and function. It suggests that either additional mechanisms are involved in regulating MMP-2 activation at the tumor cell surface, or more intriguingly, that desmoplastic fibroblasts may be the primary mediators of extracellular matrix remodeling with respect to this system.

Matrix metalloproteinases and the development of cancer

Proteolytic remodeling of the extracellular matrix is an important aspect of the creation and progression of cancer. Matrix metalloproteinases are important at several points during multi-stage neoplastic progression in tumor cells and responding blood vessels, inflammatory cells and stroma.

TGF-beta1 and Ha-Ras collaborate in modulating the phenotypic plasticity and invasiveness of epithelial tumor cells

Metastasis of epithelial tumor cells can be associated with the acquisition of fibroblastoid features and the ability to invade stroma and blood vessels. Using matched in vivo and in vitro culture systems employing fully polarized, mammary epithelial cells, we report here that TGF-beta1 brings about these changes in Ras-transformed cells but not in normal cells. When grown in collagen gels in the absence of TGF-beta, both normal and Ras-transformed mammary epithelial cells form organ-like structures in which the cells maintain their epithelial characteristics. Under these conditions, treatment of normal cells with TGF-beta results in growth arrest. The same treatment renders Ras-transformed epithelial cells fibroblastoid, invasive, and resistant to growth inhibition by TGF-beta. After this epithelial-fibroblastoid conversion, the Ras-transformed cells start to secrete TGF-beta themselves, leading to autocrine maintenance of the invasive phenotype and recruitment of additional cells to become fibroblastoid and invasive. More important, this cooperation of activated Ha-Ras with TGF-beta1 is operative during in vivo tumorigenesis and, as in wound healing processes, is dependent on epithelial-stromal interactions.

Differential expression of urokinase-type plasminogen activator, its receptor, and inhibitors in mouse skin after exposure to a tumor-promoting phorbol ester

The cellular distribution of mRNAS for urokinase-type plasminogen activator (uPA), its specific receptor (uPAR), and its inhibitors (PAI-1 and -2) in mouse skin was analyzed by in situ hybridization after topical application of the tumor promoter phorbol 12-myristate 13-acetate. In the epidermis, strong signals for uPA and PAI-1 mRNA were detected 24 h after treatment in the basal and suprabasal epidermal keratinocytes in areas with pronounced hyperproliferation and increased terminal differentiation, and in some hair follicle keratinocytes. After 48 h, both uPAR and PAI-2 mRNAs were expressed in the epidermal layers from the suprabasal keratinocytes up to the differentiating cells beneath the cornified layer and in hair follicle keratinocytes. Induction of PAI-2 mRNA was detected in epidermis as early as 3 h after treatment and remained stable for up to 7 days. In the dermis, 5 h after application of phorbol 12-myristate 13-acetate to the skin, uPA mRNA was detected in fibroblast-like cells below and around the skin muscle, and PAI-1 mRNA was detected in stromal cells located above the skin muscle. After longer exposure to phorbol 12-myristate 13-acetate, the PAI-1 mRNA-expressing stromal cells were located more superficially, apparently moving toward the epidermal layer. After 9 h, most of the PAI-1 mRNA-positive cells were identified as endothelial cells. Up to 24 h after the application of phorbol 12-myristate 13-acetate, the intensity of the signal for both uPA and PAI-1 increased, followed by a gradual decrease for up to 7 days. These results show that in mouse skin treated with a tumor-promoting phorbol ester, the various components of the plasminogen activation system are expressed by both epithelial and stromal cell types, which in dermis and subcutis are located in different places, depending on the time of exposure to the phorbol ester. Our results suggest that urokinase-mediated extracellular proteolysis has diverse functional roles during the early steps of tumor promotion.

Protein kinase C isotypes required for phorbol-ester induction of stromelysin-1 in rat fibroblasts

The phorbol-ester tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) is a potent inducer of the metalloproteinase stromelysin in fibroblasts in vivo and in several cultured cell lines. Rat-1 and Rat-2 fibroblasts, however, do not respond to TPA stimulation by induction of stromelysin gene activity, although collagenase promoter-mediated activity is induced threefold by TPA treatment in these cells. We determined that rat fibroblasts expressed protein kinase C(PKC)alpha, PKCdelta, PKCepsilon, and PKCzeta but neither the mRNA nor the protein for PKCbeta. When Rat-2 fibroblasts were stably transfected with an expression vector producing PKCbeta, however, TPA treatment of these variants resulted in a 3.1-fold induction of stromelysin promoter-mediated luciferase activity compared with a 1.3-fold induction in parental Rat-2 cells (P<0.002). Transient transfection of PKCepsilon produced a small but significant increase in TPA-stimulation of both stromelysin- and collagenase-mediated gene expression. These results suggest that there are PKC isotype-specific signaling pathways that can differentially regulate matrix metalloproteinase gene expression.

Contributions of tumor and stromal matrix metalloproteinases to tumor progression, invasion and metastasis

The malignant progression of tumors is driven by the expression of oncogenes and loss of expression of tumor suppressor genes; factors that are intrinsic to cancer cells. The phenotypic changes brought about by the gain or loss of expression of oncogenes and tumor suppressor genes lead to the acquisition of malignant traits, namely, the ability to invade into and grow in ectopic tissue environments. Recently, however, focus in cancer research has widened from the cancer cell to include the surrounding tumor stroma as an integral player in the process of tumor progression. One of the areas in cancer research contributing to this enhanced appreciation of stromal involvement in tumor progression and metastasis is that of matrix metalloproteinases (MMPs). This review provides an overview of the characteristics of MMPs and discusses their role in the progression and metastasis of tumors. Initially, attention will focus on the regulation of MMPs in tumor cells but will switch to discourse on stromal expression of MMPs in tumors and speculation on the functional consequences of stromal expression of MMPs.

Matrix metalloproteinases are expressed during ductal and alveolar mammary morphogenesis, and misregulation of stromelysin-1 in transgenic mice induces unscheduled alveolar development

The matrix-degrading metalloproteinases stromelysin-1, stromelysin-3, and gelatinase A are expressed during ductal branching morphogenesis of the murine mammary gland. Stromelysin-1 expression in particular correlates with ductal elongation, and in situ hybridization and three-dimensional reconstruction studies revealed that stromelysin-1 mRNA was concentrated in stromal fibroblasts along the length of advancing ducts. Transgenic mice expressing an activated form of stromelysin-1 under the control of the MMTV promoter/enhancer exhibited inappropriate alveolar development in virgin females. Ultrastructural analysis demonstrated that the basement membrane underlying epithelial and myoepithelial cells was amorphous and discontinuous compared with the highly ordered basal lamina in control mammary glands. Transgenic mammary glands had at least a twofold increase in the number of cells/unit area and a 1.4-fold increase in the percent of cycling cells by 13 wk of age compared with nontransgenic littermates. In addition, transgenic glands expressed beta-casein mRNA, but not protein, and resembled the proliferative and differentiated state of an animal between 8 and 10 days pregnant. An analysis of metalloproteinase expression in the glands of normal pregnant females demonstrated that the same matrix metalloproteinase family members, including stromelysin-1, were expressed in connective tissue cells surrounding epithelial clusters during the time of lobuloalveolar development. These results suggest that metalloproteinases may assist in remodeling ECM during normal ductal and alveolar branching morphogenesis, and that disruption of the basement membrane by an activated metalloproteinase can affect basic cellular processes of proliferation and differentiation.