The knee adduction moment during gait in subjects with knee osteoarthritis is more closely correlated with static alignment than radiographic disease severity, toe out angle and pain

This study tested whether the peak external knee adduction moments during walking in subjects with knee osteoarthritis (OA) were correlated with the mechanical axis of the leg, radiographic measures of OA severity, toe out angle or clinical assessments of pain, stiffness or function. Gait analysis was performed on 62 subjects with knee OA and 49 asymptomatic control subjects (normal subjects). The subjects with OA walked with a greater than normal peak adduction moment during early stance (p = 0.027). In the OA group, the mechanical axis was the best single predictor of the peak adduction moment during both early and late stance (R = 0.74, p < 0.001). The radiographic measures of OA severity in the medial compartment were also predictive of both peak adduction moments (R = 0.43 to 0.48, p < 0.001) along with the sum of the WOMAC subscales (R = -0.33 to -0.31, p < 0.017). The toe out angle was predictive of the peak adduction moment only during late stance (R = -0.45, p < 0.001). Once mechanical axis was accounted for, other factors only increased the ability to predict the peak knee adduction moments by 10 18%. While the mechanical axis was indicative of the peak adduction moments, it only accounted for about 50% of its variation, emphasizing the need for a dynamic evaluation of the knee joint loading environment. Understanding which clinical measures of OA are most closely associated with the dynamic knee joint loads may ultimately result in a better understanding of the disease process and the development of therapeutic interventions.

Bone density, dynamic joint loading and joint degeneration. A review

Increased joint loading and elevated bone density may be involved in the initiation or progression of osteoarthritis. Here, we provide an introduction to the literature on this topic and describe recent studies from our laboratories on several cohorts of subjects who had or were scheduled to have a total hip replacement for unilateral end-stage osteoarthritis. This population is very useful for studying the development and progression of osteoarthritis because of the known higher incidence of osteoarthritis in the contralateral hip than in a normal population. Separate studies of the asymptomatic contralateral hip in these subjects have shown that radiographic signs of early osteoarthritis are associated with increased bone mineral density and some of the gait adaptations typically found in subjects with end-stage osteoarthritis. We have also shown in separate studies of similar populations that elevated bone mineral density is associated with a subsequent accelerated joint space narrowing rate and that elevated hip joint loads during gait are similarly associated with an accelerated narrowing rate. Major questions yet to be answered are how joint loading and bone density interact in the development and progression of joint degeneration.

Raynaud's phenomenon

Raynaud's phenomenon is characterised by episodic vasospasm of the fingers and toes typically precipitated by exposure to cold. Mild Raynaud's is common and is not usually a harbinger of clinically important disability; its onset, however, can be startling and uncomfortable for patients, and the well recognised association in some cases with systemic rheumatic conditions often precipitates aggressive assessments for underlying diseases. Advances in vascular physiology have shed light on the role of the endothelium as well as endothelium-independent mechanisms in the altered vasoregulation of Raynaud's. We review clinical aspects of the disorder and new insights with respect to pathophysiology, and we discuss potential new therapeutics based on the disease mechanism, such as prostacyclin analogues, serotonin antagonists, and calcitonin gene-related peptides.

Coronary artery disease in systemic lupus erythematosus: A review of the literature

CONTEXT

Coronary artery occlusive disease is a common though underappreciated complication of systemic lupus erythematosus (SLE), typically a disease of young women. A case of a premenopausal patient with SLE and an acute myocardial infarction is presented, and the etiology and management of coronary artery disease in SLE reviewed.

OBJECTIVES

To review the incidence, risk factors, pathology and treatment of coronary artery disease in systemic lupus erythematosus.

DATA SOURCES

MEDLINE search of articles in English-language journals from 1980 to 2000. The index words "systemic lupus erythematosus" and the following co-indexing terms were used: "coronary artery disease," "atherosclerosis," "vasculitis," "anticardiolipin antibodies," "antiphospholipid syndrome." SELECTION SYNTHESIS AND ABSTRACTION: Papers identified were reviewed and abstracted by the authors with a presentation of a summary.

RESULTS

The prevalence of coronary artery disease among women with SLE between the ages of 35 and 44 years is at least 50-fold greater than among age-matched control subjects. Of these, coronary atherosclerosis accounts for the vast majority of cases; vasculitis of the coronary arteries and other causes generally believed to be more typical of SLE are comparatively rare.

CONCLUSIONS

The evidence suggests that SLE is a significant risk factor for coronary atherosclerosis independent of the classic risk factors of hypertension, tobacco use, and hyperlipidemia.

Tenascin-C splice variant adhesive/anti-adhesive effects on chondrosarcoma cell attachment to fibronectin

Tenascin-C is an oligomeric glycoprotein of the extracellular matrix that has been found to have both adhesive and anti-adhesive properties for cells. Recent elucidation of the two major TNC splice variants (320 kDa and 220 kDa) has shed light on the possibility of varying functions of the molecule based on its splicing pattern. Tenascin-C is prominently expressed in embryogenesis and in pathologic conditions such as tumorogenesis and wound healing. Fibronectin is a prominent adhesive molecule of the extracellular matrix that is often co-localized with tenascin-C in these processes. We studied the chondrosarcoma cell line JJ012 with enzyme-linked immunoabsorbance assays, cell attachment assays and antibody-blocking assays to determine the adhesive/anti-adhesive properties of the two major tenascin-C splice variants with respect to fibronectin and their effect on chondrosarcoma cell attachment. We found that the small tenascin-C splice variant (220 kDa) binds to fibronectin, whereas the large tenascin-C splice variant (320 kDa) does not. In addition, the small tenascin-C splice variant was found to decrease adhesion for cells when bound to fibronectin, but contributed to adhesion when bound to plastic in fibronectin-coated wells. Antibody blocking experiments confirmed that both the small tenascin-C splice variant and fibronectin contribute to cell adhesion when bound to plastic. The large tenascin-C splice variant did not promote specific cell attachment. We hypothesize that the biologic activity of tenascin-C is dependent on the tissue-specific splicing pattern. The smaller tenascin-C isoform likely plays a structural and adhesive role, whereas the larger isoform, preferentially expressed in malignant tissue, likely plays a role in cell egress and metastasis.

Efficacy and safety of intraarticular sodium hyaluronate in knee osteoarthritis. ORTHOVISC Study Group

A prospective, multicenter, randomized, double-blind, controlled trial was conducted in 226 patients with knee osteoarthritis to evaluate the safety and efficacy of intraarticular injections of sodium hyaluronate. Patients were randomized to three weekly injections of 30 mg sodium hyaluronate or physiologic saline (control) and were observed for an additional 25 weeks. In comparison with the control group, among patients who completed at least 15 weeks of the study and whose Western Ontario and McMaster Universities Osteoarthritis Index pain score for the contralateral knee was less than 12 at baseline, sodium hyaluronate injection resulted in improvement in Western Ontario and McMaster Universities Osteoarthritis Index pain score, patient and investigator global assessments, and pain on standing from Weeks 7 to 27. Fifty-eight percent of patients treated with sodium hyaluronate achieved a 5-unit or greater improvement in mean pain score from Weeks 7 through 27, compared with 40% of control patients. In addition, nearly twice as many patients treated with sodium hyaluronate as with saline (30% versus 17%, respectively) achieved a net improvement of at least 7 units. In contrast to treatment with saline, Western Ontario and McMaster Universities Osteoarthritis Index pain score for the contralateral knee was inversely related to the magnitude of improvement after treatment with sodium hyaluronate. Few side effects were attributed to treatment, and no differences between treatment groups were seen in this respect (sodium hyaluronate, nine [8%]; saline, 11 [10%]). The incidence of injection site reactions was low (sodium hyaluronate, 1.2 %; saline, 1.5%). The results indicate that sodium hyaluronate treatment is well tolerated and produces statistically and clinically significant improvement of symptoms in patients with mild to moderate knee osteoarthritis in whom pain in the contralateral knee is relatively modest.

Two-year effects of alendronate on bone mineral density and vertebral fracture in patients receiving glucocorticoids: a randomized, double-blind, placebo-controlled extension trial

OBJECTIVE

To evaluate the continued efficacy and safety of alendronate (ALN) for up to 2 years in patients receiving glucocorticoids.

METHODS

This is a 12-month extension of a previously completed 1-year trial of daily ALN, performed to evaluate the effects of ALN over a total of 2 years in 66 men and 142 women continuing to receive at least 7.5 mg of prednisone or equivalent daily. All patients received supplemental calcium and vitamin D. The primary end point was the mean percentage change in lumbar spine bone mineral density (BMD) from baseline to 24 months. Other outcomes included changes in hip and total body BMD, biochemical markers of bone turnover, radiographic joint damage of the hands, and vertebral fracture incidence.

RESULTS

The mean (+/-SEM) lumbar spine BMD increased by 2.8 +/- 0.6%, 3.9 +/- 0.7%, and 3.7 +/- 0.6%, respectively, in the groups that received 5 mg, 10 mg, and 2.5/10 mg of ALN daily (P < or = 0.001) and decreased by -0.8 +/- 0.6% in the placebo group (P not significant) over 24 months. In patients receiving any dose of ALN, BMD was increased at the trochanter (P < or = 0.05) and maintained at the femoral neck. Total body BMD was increased in patients receiving 5 or 10 mg ALN (P < or = 0.01). These 2 dose levels of ALN were more effective than placebo at all sites (P < or = 0.05). Bone turnover markers (N-telopeptides of type I collagen and bone-specific alkaline phosphatase) decreased 60% and 25%, respectively, during treatment with ALN (P < or = 0.05). There were fewer patients with new vertebral fractures in the ALN group versus the placebo group (0.7% versus 6.8%; P = 0.026). The safety profile was similar between treatment groups.

CONCLUSION

Alendronate is an effective, well-tolerated therapy for the prevention and treatment of glucocorticoid-induced osteoporosis, with sustained treatment advantages for up to 2 years.

Alterations in the regulatory pathway involving p16, pRb and cdk4 in human chondrosarcoma

The G1 regulatory pathway involving p16, pRb and cdk4 in the cell cycle has been investigated in human chondrosarcoma. The protein expression of p16, pRb and cdk4 was analyzed by Western blot in cultured cells from eight chondrosarcomas and in two chondrosarcoma cell lines. Both cell lines and one other sample were negative for p16. Moreover, one of the cell lines was pRb-negative and showed a high expression of cdk4 as well. In the other cell line and in three other samples pRb of expected size were detected in addition to a shorter form of the protein. To further investigate the reasons for down-regulation of the p16 protein, the p16-coding gene CDKN2 was analyzed by polymerase chain reaction (PCR), methyl-specific PCR (MSP) and sequencing in all tumor samples as well as in corresponding tumor tissues from three of the samples. The p16-negative samples were all found to have homozygous deletion of CDKN2. Another sample showed partial gene methylation and a heterozygous position in codon 148 was detected in one sample. The same base substitution was also found in two of the tissue samples. Finally, cytogenetic analysis of the samples with homozygously deleted CDKN2 revealed multiple structural abnormalities in all three cases. In conclusion, the p16/pRb/cdk4 pathway may play an important role in the pathogenesis of some chondrosarcomas.

Two-year effects of alendronate on bone mineral density and vertebral fracture in patients receiving glucocorticoids: a randomized, double-blind, placebo-controlled extension trial

OBJECTIVE

To evaluate the continued efficacy and safety of alendronate (ALN) for up to 2 years in patients receiving glucocorticoids.

METHODS

This is a 12-month extension of a previously completed 1-year trial of daily ALN, performed to evaluate the effects of ALN over a total of 2 years in 66 men and 142 women continuing to receive at least 7.5 mg of prednisone or equivalent daily. All patients received supplemental calcium and vitamin D. The primary end point was the mean percentage change in lumbar spine bone mineral density (BMD) from baseline to 24 months. Other outcomes included changes in hip and total body BMD, biochemical markers of bone turnover, radiographic joint damage of the hands, and vertebral fracture incidence.

RESULTS

The mean (+/-SEM) lumbar spine BMD increased by 2.8 +/- 0.6%, 3.9 +/- 0.7%, and 3.7 +/- 0.6%, respectively, in the groups that received 5 mg, 10 mg, and 2.5/10 mg of ALN daily (P < or = 0.001) and decreased by -0.8 +/- 0.6% in the placebo group (P not significant) over 24 months. In patients receiving any dose of ALN, BMD was increased at the trochanter (P < or = 0.05) and maintained at the femoral neck. Total body BMD was increased in patients receiving 5 or 10 mg ALN (P < or = 0.01). These 2 dose levels of ALN were more effective than placebo at all sites (P < or = 0.05). Bone turnover markers (N-telopeptides of type I collagen and bone-specific alkaline phosphatase) decreased 60% and 25%, respectively, during treatment with ALN (P < or = 0.05). There were fewer patients with new vertebral fractures in the ALN group versus the placebo group (0.7% versus 6.8%; P = 0.026). The safety profile was similar between treatment groups.

CONCLUSION

Alendronate is an effective, well-tolerated therapy for the prevention and treatment of glucocorticoid-induced osteoporosis, with sustained treatment advantages for up to 2 years.

Osteoarticular tuberculosis: current diagnosis and treatment

Tuberculous synovitis frequently presents as a monoarthritis of weight-bearing joints such as the hip, knee, or ankle. Owing to its low incidence in developed countries, the diagnosis is often delayed for months to years. Early diagnosis with a synovial biopsy permits prompt antituberculous therapy and substantially improves the prospect of preservation of joint structure and function. Initial treatment typically includes combination therapy with four drugs (isoniazid, rifampin, pyrazinamide, and streptomycin or ethambutol) because of the frequency of isoniazid resistance. Antimicrobial therapy should be of at least 9 months' duration, longer in immunocompromised hosts. Partial synovectomy and other surgical procedures should be restricted to joints with severe cartilage destruction, large abscesses, joint deformity, multiple drug resistance, or atypical mycobacteria.

Scleroderma lung: pathogenesis, evaluation, and current therapy

Interstitial lung disease (ILD) is now the most common cause of mortality in scleroderma, although its pathogenesis remains poorly understood. Management requires early detection and treatment before the onset of lung fibrosis. In a number of uncontrolled studies, the combination of daily oral cyclophosphamide and low-dose prednisone appears to be effective, although these conclusions have yet to be confirmed.

Marshall Urist Award. Interstitial collagenase gene expression correlates with in vitro invasion in human chondrosarcoma

Matrix metalloproteinases contribute to the processes of local invasion and metastasis by providing cells with the ability to traverse tissue boundaries. The levels of gene expression were quantitated for matrix metalloproteinases-1 and tissue inhibitors of metalloproteinases-1 in human chondrosarcoma cell lines, and the results were correlated with cell differentiation, collagenase activity, and in vitro invasion. Three well characterized human cell lines were used in this study, with the level of chondrocytic differentiation confirmed to be JJ012, FS090, and 105KC in increasing order on the basis of aggrecan and collagen gene expression. The matrix metalloproteinases-1/tissue inhibitors of metalloproteinases-1 ratio correlated with the level of differentiation in an inverse fashion. Collagenase activity paralleled matrix metalloproteinases-1/tissue inhibitors of metalloproteinases-1 gene expression and was associated with a more invasive phenotype in an in vitro assay. In this report, matrix metalloproteinase-1 and tissue inhibitors of metalloproteinases-1 expression in human chondrosarcoma tumor cell lines were quantitated, and it was shown that interstitial collagenase gene expression correlates inversely with chondrocytic differentiation. Differences in collagenase activity and in vitro invasion correlate inversely with the level of differentiation. These findings are consistent with the hypothesis that collagenase activity is associated with a poorer prognosis in chondrosarcoma by facilitating cell egress from the tumor matrix.

Knee pain and joint loading in subjects with osteoarthritis of the knee

Although treatments for osteoarthritis of the knee are often directed at relieving pain, pain may cause patients to alter how they perform activities to decrease the loads on the joints. The knee-adduction moment is a major determinant of the load distribution between the medial and lateral plateaus. Therefore, the interrelationship between pain and the external knee-adduction moment during walking may be especially important for understanding mechanical factors related to the progression of medial tibiofemoral osteoarthritis. Fifty-three subjects with symptomatic radiographic evidence of osteoarthritis of the knee were studied. These subjects were a subset of those enrolled in a double-blind study in which gait analysis and radiographic and clinical evaluations were performed after a 2-week washout of anti-inflammatory and analgesic treatment. The subjects then took a nonsteroidal anti-inflammatory drug, acetaminophen, or placebo for 2 weeks, and the gait and clinical evaluations were repeated. The change in the peak external adduction moment between the two evaluations was inversely correlated with the change in pain (R = 0.48, p < 0.001) and was significantly different between those whose pain increased (n = 7), decreased (n = 18), or remained unchanged (n = 28) (p = 0.009). Those with increased pain had a significant decrease in the peak external adduction (p = 0.005) and flexion moments (p = 0.023). In contrast, the subjects with decreased pain tended to have an increase in the peak external adduction moment (p = 0.095) and had a significant increase in the peak external extension moment (p = 0.017). The subjects whose pain was unchanged had no significant change in the peak external adduction (p = 0.757), flexion (p = 0.234), or extension (p = 0.465) moments. Thus, decreases in pain among patients with medial tibiofemoral osteoarthritis were related to increased loading of the degenerative portion of the joints. Additional long-term prospective studies are needed to determine whether increased loading during walking actually results in accelerated progression of the disease.

Quantification of progressive joint space narrowing in osteoarthritis of the hip: longitudinal analysis of the contralateral hip after total hip arthroplasty

OBJECTIVE

The rate of progressive joint space narrowing in the contralateral hip after total hip arthroplasty (THA) for osteoarthritis (OA) and the factors which may predispose patients to more aggressive joint space narrowing remain undefined. The current study sought to evaluate the rate and pattern of, and risk factors for, progressive joint space narrowing in the contralateral hip after THA for OA.

METHODS

Each patient who underwent THA for OA in 1984-1985 was followed up longitudinally, and annual anteroposterior (AP) pelvis radiographs were obtained. The radiographic joint space width (JSW) of each contralateral hip joint was quantified, and the rates of JSW narrowing were determined. Evaluation of potential risk factors for accelerated progression of joint space narrowing included age, sex, side of surgery, weight, height, body mass index (BMI), hip pain, etiology of OA, and Kellgren/Lawrence radiographic grade.

RESULTS

Ninety-nine patients and 619 AP pelvis radiographs were evaluated. The median initial JSW was 3.48 mm (interquartile range 1.55). JSW declined in a linear manner at a median rate of 0.10 mm/year. The rate of decline between baseline and followup in 20 months was predictive of the overall slope. Two subpopulations were identified. Eighty-five percent of patients maintained a slow decline in JSW (< or =0.2 mm/year), and 15% exhibited an accelerated decline in JSW (>0.2 mm/year). Kellgren/ Lawrence radiographic grade > or =2 and a diagnosis of primary OA were each associated with a more rapid decline in JSW (P = 0.006 and P = 0.02, respectively). Initial JSW, age, sex, weight, height, BMI, and hip pain were not risk factors for rapid decline in JSW.

CONCLUSION

Radiographic hip JSW may be reliably quantified and followed up longitudinally using standard AP radiographs. Progression of JSW narrowing in the contralateral hip after THA for OA proceeds in a linear manner over several years. A subpopulation of patients with accelerated narrowing of contralateral JSW may be identified within 20 months, and may represent a suitable population with which to assess the potential efficacy of new disease-modifying agents.

Bone mineral density varies as a function of the rate of joint space narrowing in the hip

OBJECTIVE

To determine whether patients with a rapid rate of joint space narrowing (JSN) in the hip have higher initial bone mineral density (BMD) in the proximal femur and/or lumbar spine than corresponding patients with a slow rate of JSN.

METHODS

Twenty-eight patients undergoing unilateral total hip replacement (THR) for osteoarthritis (OA), but whose contralateral hips were asymptomatic and had minimal or no radiographic OA, were evaluated. The contralateral proximal femur (i.e., non-operated hip) and lumbar spine were scanned by dual energy x-ray absorptiometry at baseline (prior to THR) and at 2 years. The rate of JSN was determined by serial longitudinal quantification of the joint spaces over the 2 year period following THR from conventional radiographs, and the patients were divided into a group with a slow rate of JSN (< or = 0.2 mm/yr, n = 20) and a group with a rapid rate of JSN (> 0.2 mm/yr, n = 8).

RESULTS

The baseline BMD z and t scores at the femoral neck, Ward's triangle, and lumbar spine of the patients with subsequent rapid rates of JSN were significantly higher than those of patients with slower rates (p < 0.05). There was no difference between the rapid and slow narrowers at the greater trochanter (p > 0.2). Age, sex, weight, height, body mass index, Kellgren- Lawrence scores, and initial joint space width were not significantly different between the 2 groups.

CONCLUSION

Patients with a rapid rate of JSN of the asymptomatic hip after unilateral THR are characterized by elevated local and remote BMD. The local elevation in BMD implies that increased local bone density may contribute to or serve as a marker for increased risk of development of OA (assuming that JSN can be used as a predictive marker). The presence of elevated BMD in the spine suggests that there are systemic as well as local aspects of OA pathogenesis, at least in patients with one THR and rapid JSN in the contralateral hip.

Multidrug resistance-1 and p-glycoprotein in human chondrosarcoma cell lines: expression correlates with decreased intracellular doxorubicin and in vitro chemoresistance

We report on two chondrosarcoma cell lines, FS and AQ, that may be used as models of multidrug resistance in chondrosarcoma. Multidrug resistance-1 expression was assayed with reverse transcription-polymerase chain reaction. Immunostaining for the multidrug resistance-1 product, P-glycoprotein, was performed with the monoclonal antibody C494. Intracellular levels of doxorubicin were measured by fluorescent emission at 590 nm after 1 hour of incubation with the agent and again after 1, 2, and 4-hour washout periods. Chemosensitivity was assayed by staining micropellet cultures of AQ and FS cells with fluorescein acetate before and after the cells were exposed to varying doses of doxorubicin for 48 hours. Cytotoxicity was assessed by comparison of computer-processed images before and after treatment. The FS cell line was positive for multidrug resistance-1 expression, stained heavily for P-glycoprotein, and had significantly lower intracellular levels of doxorubicin than the AQ cell line, which was negative for multidrug resistance-1 and P-glycoprotein. Chemosensitivity testing showed that the FS cell line was significantly more resistant to doxorubicin than was the AQ cell line at all doses tested. Our results show that multidrug resistance-1 expression in a human chondrosarcoma cell line results in resistance to doxorubicin in vitro.

The Prosorba column for treatment of refractory rheumatoid arthritis: a randomized, double-blind, sham-controlled trial

OBJECTIVE

To evaluate the efficacy and safety of the Prosorba column as a treatment for rheumatoid arthritis (RA) in patients with active and treatment-resistant (refractory) disease.

METHODS

A sham-controlled, randomized, double-blind, multicenter trial of Prosorba versus sham apheresis was performed in patients with RA who had failed to respond to treatment with methotrexate or at least 2 other second-line drugs. Patients received 12 weekly treatments with Prosorba or sham apheresis, with efficacy evaluated 7-8 weeks after treatment ended. Patients were characterized as responders if they experienced improvement according to the American College of Rheumatology (ACR) response criteria at the efficacy time point. A data safety monitoring board (DSMB) evaluated interim analyses for the possibility of early completion of the trial.

RESULTS

Patients in the trial had RA for an average of 15.5 years (range 1.7-50.6) and had failed an average of 4.2 second-line drug treatments prior to entry. After the completion of treatment of 91 randomized patients, the DSMB stopped the trial early due to successful outcomes. Of the 47 patients in the Prosorba arm, 31.9% experienced ACR-defined improvement versus 11.4% of the 44 patients in the sham-treated arm (P = 0.019 after adjustment for interim analysis). When results from 8 additional patients, who had completed blinded treatments at the time of DSMB action, were added to the analysis (n = 99), results were unchanged. The most common adverse events were a short-term flare in joint pain and swelling following treatment, a side effect that occurred in most subjects at least once in both treatment arms. Other side effects, although common, occurred equally as frequently in both treatment groups.

CONCLUSION

Apheresis with the Prosorba column is an efficacious treatment for RA in patients with active disease who have failed other treatments.

Therapeutic approaches to osteoarthritis

Management is multifaceted: Palliation of pain should be accompanied by physical and occupational therapy and use of adaptive devices to improve performance. New techniques aim to interrupt disease progression and to induce biologic repair.

Chromosome 9 related aberrations and deletions of the CDKN2 and MTS2 putative tumor suppressor genes in human chondrosarcomas

Deletions on the short arm of chromosome 9 (9p21 region) have been reported in a number of hematopoietic and solid tumors. These aberrations on 9p have been previously associated with the loss of the interferon gene cluster and the gene for methylthioadenosine phosphorylase (MTAP), localized to the 9p21-22 region. Recently, two putative tumor suppressor gene(s) CDKN2 and MTS2 have been mapped to the 9p21 region, and shown to be deleted in a large number of tumors including leukemias, melanomas, bladder cancers and brain tumors. We have previously reported a similar 9p21 abnormality and deletions of the CDKN2 and MTS2 genes in a myxoid chondrosarcoma cell line and its subclones. In this study we report consistent abnormalities of chromosome 9 in additional chondrosarcomas examined by a detailed cytogenetic and molecular analysis. Seven chondrosarcoma cell lines, one primary chondrosarcoma, and a benign chondroma were examined. Four of the seven tumor cell lines examined showed grossly visible aberrations of chromosome 9. Molecular analysis of these chondrosarcoma cell lines revealed hemizygous deletions of the interferon genes, and the absence of the MTAP gene, protein or activity. In addition, four of the seven chondrosarcoma cell lines also showed deletions of the CDKN2 and/or MTS2 putative tumor suppressor genes, or the absence of the CDKN2 protein product. No such chromosome 9 related aberrations were detected in the benign chondroma. These data suggest that chromosome 9p21 abnormality, and deletions of the CDKN2 and MTS2 tumor suppressor genes may be a significant event in the development of chondrosarcomas.

Partial deletions of the CDKN2 and MTS2 putative tumor suppressor genes in a myxoid chondrosarcoma

Cytogenetic abnormalities of chromosome 9 (9p21) have been reported in a large number of tumors that include malignant melanomas, gliomas, lung cancers and leukemias. These aberrations on 9p have been previously shown to involve the loss of the interferon gene cluster and the gene for methylthioadenosine phosphorylase (MTAP), both of which have been mapped to the 9p21 region. Recently, two putative tumor suppressor gene(s) CDKN2 and MTS2, have been mapped to the 9p21 region, and have been shown to be deleted in a large number of hematopoietic and solid malignancies. In this study we report a cytogenetic and a detailed molecular analysis of a myxoid chondrosarcoma cell line 105KC and its clonal derivatives 105AJ, 105AJ1.1, 105AJ3.1, and 105AJ5.1. Specifically, we have demonstrated chromosome 9p21 related abnormalities by cytogenetic analysis, the associated loss of the interferon gene cluster, and the loss of the immunoreactive MTAP protein and activity. In addition, we have also shown the presence of deletions involving the CDKN2 and the MTS2 putative tumor suppressor genes in these chondrosarcoma cell lines. The above studies were extended to other chondrosarcoma cell lines and primary tumors, where similar deletions of the CDKN2 and MTS2 genes were found to be present (unpublished data). This suggests a potential role for the involvement of the CDKN2 and MTS2 putative tumor suppressor genes in the development of chondrosarcomas.