Chondrosarcoma, a malignant cartilage-forming mesenchymal tumor, displays a wide range of clinical behavior that can be difficult to predict with histological analysis 12. These tumors account for approximately 25% of all malignant tumors arising from the skeletal system 3, but are considered by most authorities to involve the jaws only rarely; probably less than 1% of all chondrosarcomas arise in the head and neck area 4.

Controversies surrounding the relationship between chondrosarcoma of the jaws and chondrosarcoma of the skeleton have revolved around their biologic behavior, histopathological features and clinical response to conservative therapy. Chondrosarcoma of jaws is locally aggressive with a high recurrence rate but rarely metastasize to distant sites 5. If chondrosarcoma spreads from its primary site (i.e., metastasizes), it usually spreads to the lungs. Metastasis is rare with low-grade tumors, but has been seen, even up to 10 years after diagnosis 6. About half of grade III and nearly all dedifferentiated chondrosarcomas will metastasize. Up to 13% of recurrent chondrosarcomas are of a higher grade than the original neoplasm 78.

Conventional chondrosarcomas can be categorized according to their location in bone into central, peripheral, and juxtacortical chondrosarcomas. Rare subtypes of chondrosarcoma, including dedifferentiated, mesenchymal, and clear cell chondrosarcoma are discerned, together constituting 10%–15% of all chondrosarcomas 9. Clear cell chondrosarcoma is a low -grade malignant tumor and tends to metastasis rarely 10. While, aggressive chondrosarcoma subtypes, such as dedifferentiated and mesenchymal chondrosarcomas bear a poor prognosis 11.

Histological grading is the best and most commonly used marker at present for the prognosis of chondrosarcomas; however, it is also subject to interobserver variability 12. This is worrisome, because therapy for grade I and grade II chondrosarcoma may differ. Wide surgical excision remains the best available treatment for intermediate-to high-grade tumors 9. Most treatment failures are due to local recurrences 5.

Currently, treatment decisions in chondrosarcomas are guided by clinical-pathological factors such as age, sex, metastasis, recurrence, and histological grade. Although useful, these factors fail to provide definitive information regarding the overall aggressiveness of a tumor and its potential to recur. In theory, a factor that consistently identified patients at risk for recurrent disease would help to improve disease-free survival by allowing physicians to select high-risk patients for more aggressive treatment. In addition, identification of a biological marker of aggressive disease would help to provide new avenues for rational drug design targeted against specific molecular defects 13.

In recent years, several biologic markers have been identified that they may provide additional diagnostic and prognostic information in the management of chondrosarcomas 14.

The matrix metalloproteinases (MMPs) comprise a family of at least 25 enzymes that degrade the extracellular matrix 15. These enzymes operate during normal development in tissue differentiation and remodeling 1617, but are also active under pathological conditions to cause inflammatory disease, degradation of bone 18 and cartilage 19, as well as tumor metastasis 2021. They are secreted as inactive latent forms, depend upon a zinc-binding active site, and are inhibited by specific proteins referred to as the tissue inhibitors of matrix metalloproteinases or TIMPs 222324. In general, these MMPs enzymes are classified according to their substrate specificity and structural similarities 252627. There are four major subgroups: (a) the collagenases degrade collagen types I, II and III 25, (b) the gelatinases act on types IV, V, VII and X collagens 28, (c) elastin and the stromelysins shows a broader specificity, acting on proteoglycans, laminin, and fibronection 26 and (d) MT-MMPs that represent membrane-bound forms of the enzymes, which activate latent MMP-2 and can cleave collagen at the classic site 29. MMPs expression is differentially regulated by several growth factors 18.

Human collagenase-3 (MMP-13) is a recently identified member of the matrix metalloproteinase (MMP) family that was originally isolated from breast carcinoma 30. Biochemical characterization of colloagenase-3 has revealed that it is a very potent enzyme that, after activation through a proteolytic cascade mechanism, displays a broad spectrum of activity against connective tissue components 31. In addition to its proteolytic activity on fibrillar collagens, collagenase-3 is also a powerful gelatinase and may thus contribute to further degradation the initial cleavage products of collagenolysis to small fragments suitable for further metabolism 32. Very recent studies have provided that collagenase-3 may also degrade the large cartilage proteoglycan aggrecan 33 and other components of the extracellular matrix and basement membranes, including type IV collagen, fibronectin, and tenascin 34.

Preliminary studies on the prognostic value of collagenase-3 in breast cancer have revealed that this enzyme is a marker of poor clinical outcome in breast cancer patients 35. In addition, recent studies have shown that collagenase-3 is also over-expressed by a subset of squamous cell carcinomas with extensive local invasion 363738, but has only rarely been described in connective tissue tumors 3940. To date, there have been no reported among the English language literature describing the possible production of this enzyme by chondrosarcoma of the jaws. In this regard, the finding that collagenase-3 is produced by chondrocytes during human fetal development 4142 and in joint-destructive processes 4344 prompted us to examine the possibility that this enzyme could be also associated with tumor processes involving these cells. The present study was designed to evaluate MMP-13 immunohistochemistry for its presence in a series of chondrosarcoma of the jaws as well as normal cartilage. It is also aimed to investigate relation between its expression and clinico-pathological parameters of this tumor.

Patients with chondrosarcoma of the jaws were treated by surgical resection as a primary means of disease control. Of the treated patients, eleven had archival paraffin-embedded specimens and adequate clinical history to enable the following study. They were selected from paraffin blocks archives of Oral and General Pathology Departments, Faculty of Dentistry and Faculty of Medicine, Mansoura University between 1998 to 2006. All cases did not previously receive chemo-or radiotherapy before the operation. Chondrosarcomas were graded according to WHO classification 45. The grading is based primarily on nuclear size of tumor cells, nuclear staining (hyperchromasia, or darker staining of nuclear material) and cellularity. Mitotic figures and necrosis are additional features useful in grading.

Two cases of normal cartilage were obtained from condylar cartilage of a mandible recommended for hemimandibulectomy due to evidence of squamous cell carcinoma lesion.

Human collagenase-3 (MMP-13), a new member of the MMP family, is expressed by breast tumors 30. It is a powerful collagenolytic and gelatinolytic enzyme that preferentially cleaves type II collagen and it can therefore be implied that this enzyme may play a considerable role in connective tissue turnover 32. MMP-13 plays an important role in tumor progression in numerous human malignancies 48, including colorectal cancer 49, breast cancer 30, squamous cell carcinomas 3637, and melanoma 50.

Absence of MMP-13 expression in normal cartilage 4142434445464748495051 may be explained by the destruction of MMP-13 by other peptidases related to digestion or possibly due to the very low rate of its synthesis in this tissue 52. Also, it might be due to the prolonged duration of the slow process of ossification that is preceded by cartilage matrix degradation by this collagenase 4142. Normally, MMP-13 expression by chondrocytes appears to be limited to cartilage development. Chondrocytes produce MMP-13 to remove type II collagen at the growth plate during bone formation 4142. Whereas neoplastic chondrocytes were the most immunoreactive cells in the tumor sections examined. The involvement of chondrocytes in MMP-13 production in chondrosarcoma of jaws is related to their roles in matrix turnover 323334353637383940414243444546474849505152. Chondrocytes maintain the integrity of the cartilage in normal joints, but in the pathological conditions, chondrocytes are influenced to change their properties by the action of inflammatory cytokines to begin secreting matrix-degrading enzymes and to eventually cause tumor. Therefore, the relative role of collagenase-3 in chondrosarcoma becomes important 53.

In the current study, it is of interest that, despite the fact that most of analyzed chondrosarcoma cases were positive for MMP-13 expression, there were clear variations in the percentage of positive cells and the intensity of staining. The highest collagenase-3 (MMP-13) positive immunoreactivity was found among grade III chondrosarcoma cases. While, the weakest reaction for MMP-13 was noted in most cases of grade I chondrosarcoma. In accordance with Uria et al 54, these variation in MMP-13 staining intensity may be dependant on the biological behavior and histopathological features (degree of cellularity and pleomorphism) in this tumor.

Staining for MMP-13 is usually cytoplasmic but nuclear staining was also seen in some cases. This finding was in accordance with the results of other reports 49, its significance is undetermined, but its presence warrants documentation. This observation may be attributed to MMP-13 Ab used here is over expressed in its early stages in the nucleus or it may possibly due to alteration in the processing or stability of MMP-13. Strong expression of cytoplasmic and nuclear MMP-13 was observed with high grade tumors. Thus, nuclear MMP-13 staining may help to identify a category with worse prognosis in this tumor.

Strong immunoreactivity of MMP-13 in chondrocytes located near blood vessels may be due to increased response of malignant chondrocytes to the inductive effect of the stimulatory factors produced by endothelial cells such as different cytokines (IL-1β, TGF-β or TNF-α) 181920212223242526272829303132333435363738394041424344454647484950515253545556. These factors were previously found to play important roles in the induction of collagenase-3 in fibroblasts, keratinocytes, or primary chondrocytes 394041424344454647484950515253.

MMP-13 is over-expressed in breast carcinomas but not in normal mammary gland nor in benign mammary lesions 3031323334353637383940414243444546474849505152535455565758. Additional reports revealed similar results among squamous cell carcinomas 181920212223242526272829303132333435363738394041424344454647484950515253545556 and malignant melanoma 50. This observation suggests that up-regulation of MMP-13 may be somewhat linked to the malignant transformation and contribute to the progression of these tumors 54. MMP-13 could play a critical role in the uncontrolled lytic processes occurring during malignant progression. This possibility is consistent with biochemical properties of this enzyme which has been characterized as a potent proteinase with a wide substrate specificity including a preferential degrading activity on type II collagen 3132333435363738394041424344 which is the most abundant type in articular cartilage 6061.

The increase in MMP-13 expression may be necessary for the activation of other MMPs that have previously been identified in chondrosarcoma such as MMP-2 and MMP-9 62 it is also activated by MMP-2, MMP-3, and MTI-MMP 32. Furthermore, it is logical that tumors have far higher amounts of MMP-13 activity because this molecule catalyses the breakdown of ECM necessary for invasion. Similarly, normal chondrocytes have no requirement for MMP-13 mediated ECM breakdown, or increased activation of other MMPs. These findings again strengthen the link between MMP-13 expression and tumor progression.

The mechanisms involved in MMP-13 activation are complex. Previous investigations reported that the production of a growth factor called basic fibroblast growth factor (bFGF) by the malignant chondrocytes that stimulates the same cell to produce collagenase-3 (MMP-13) 232425262728293031323334353637383940414243444546474849505152535455565758596061626364. This factor might be responsible for the currently observed increase expression of MMP-13 among the high-grade cases of chondrosarcoma of jaws. The precise molecular mechanisms responsible for collagenase-3 up-regulation in chondrosarcoma cells in response to bFGF have not yet been elucidated, although it is likely that members of the FGF receptor family may be involved 62636465. The availability of a phenotypically stable chondrosarcoma cell line with ability to produce collagenase-3 after bFGF treatment will be very helpful for further evaluation. The precise mechanisms mediating the bFGF elicited induction of this MMP gene in human chondrosarcoma 54. These variations need further investigations to reveal possible implication to the clinical outcome.

Fong et al., 40 found that there was no significant association between MMP-13 expression and patient's age, tumor site and local recurrence in chondrosarcomas. This result was in accordance with our results.

A finding of particular interest in this study was the occurrence of positive MMP-13 in most of the mitotically active cells. This finding may reflect the high expression of MMP-13 in the cases with high score of mitosis. Accordingly, it can be claimed that the presence of MMP-13 might be associated with proliferative activity and tumor aggressiveness 50.

A significant association between MMP-13 expression and patient's poor prognosis was observed in this study. This finding was in agreement with previous reports on breast carcinoma 35, oral squamous cell carcinoma 37 and malignant melanoma 50. On the contrary, others 14 have found no correlation between MMP-13 over-expression and prognosis in chondrosarcoma. This confliction can be attributed to variables in ethnic and environmental factors influencing the tumor growth in different populations. However, the number of the cases that examined in the present work is small to consider this a true confliction.

The ability to predict the biologic behavior of cartilaginous neoplasms has been difficult and many studies have sought to identify a marker for recurrence 6667. The expression of MMP-13 was present in all the examined specimens. However, it could not be correlated with disease recurrence. This result was in agreement with Scully et al., 68 who found that the expression of MMP-13 has no prognostic significance for recurrence in chondrosarcoma. It has been reported that as a tumor dedifferentiates and becomes more aggressive biologically, there is a phenotypic drift that results in increased amounts of type I collagen being synthesized 6970. It is possible that specificity for cleavage of type I collagen may be more important than that of type II collagen to permit cell egression and this is what leads to the observed results.

The understanding of cancer pathogenesis is rapidly growing and evidence indicates that several molecular genetic markers are involved in the initiation and/or progression of the disease. The interactions of the molecular genetic changes are complex; however, some may be important targets for the development of specific inhibitors to serve as potential chemotherapeutic agents. An extracellular matrix and basement membrane turnover is regulated by a delicate balance between the molecular factors that participate in the production, activation, and inhibition of MMPs and the production of natural tissue inhibitors of matrix metalloproteinases (TIMPs) 71. Because of their central role in tumor invasion and metastasis, MMPs are potential targets for therapeutic intervention. Several investigations have demonstrated the effectiveness of anti-MMP therapy 72. A synthetic small molecule has been shown to inhibit the endotoxin and cytokine-induced synthesis of MMP 73. The inhibition of MMPs such as MMP-13 has produced encouraging results by decreasing the number, size and speed of development of metastatic nodules in animals 74. In the present study, the MMP-13 expression was detected in 72.8 % of the samples. The fact that MMP-13 activation is likely to occur in chondroasrcoma of the jaws may make it particularly suitable for treatment with the emerging class of drugs to block MMP-13 secretion and matrix invasion. Using MMP-13 inhibition as one arm of a multitargeted approach will have benefits for the treatment of chondroasrcoma of the jaws, when a larger series of studies confirms MMP-13 representation in these tumors. In addition, considering the many factors involved such as tissue inhibitors of metalloproteinases (TIMPs) or various stimulating factors for MMPs, the relationship between chondroasrcoma of the jaws and TIMPs and other subtypes of MMPs in worthy of further studies.

1- On the basis of positive expression of MMP-13 in the majority of chondrosarcoma of the jaws and absence of detectable expression in normal cartilage, a possible role for this metalloproteinase in the tumoral process is proposed.

2- The present study provides evidence of the prognostic significance of MMP-13 in chondrosarcoma of the jaws where the association between this marker and mitotic counts, necrosis and high grade tumors suggests the possible role of MMP-13 in determining the highly aggressive tumors.

3- It may become a therapeutic target for jaws chondrosarcoma's patients with MMP-13 positive tumor.

These results are preliminary because of the small sample size and should be verified in a larger number of cases. Further exploration of these findings and correlation with clinical follow-up are needed to corroborate these associations. Similarly, it will be of interest to examine whether the small percentage of benign lesions producing MMP-13 could be indicative of an increased risk of malignant transformation in these patients.