Molecularly matched therapy in the context of sensitivity, resistance, and safety; patient outcomes in end-stage cancer - the MetAction study

Background: In precision cancer medicine, the challenge is to prioritize DNA driver events, account for resistance markers, and procure sufficient information for treatment that maintains patient safety. The MetAction project, exploring how tumor molecular vulnerabilities predict therapy response, first established the required workflow for DNA sequencing and data interpretation (2014-2015). Here, we employed it to identify molecularly matched therapy and recorded outcome in end-stage cancer (2016-2019).Material and methods: Metastatic tissue from 26 patients (16 colorectal cancer cases) was sequenced by the Oncomine assay. The study tumor boards interpreted called variants with respect to sensitivity or resistance to matched therapy and recommended single-agent or combination treatment if considered tolerable. The primary endpoint was the rate of progression-free survival 1.3-fold longer than for the most recent systemic therapy. The objective response rate and overall survival were secondary endpoints.Results: Both common and rare actionable alterations were identified. Thirteen patients were found eligible for therapy following review of tumor sensitivity and resistance variants and patient tolerability. The interventions were inhibitors of ALK/ROS1-, BRAF-, EGFR-, FGFR-, mTOR-, PARP-, or PD-1-mediated signaling for 2-3 cases each. Among 10 patients who received treatment until radiologic evaluation, 6 (46% of the eligible cases) met the primary endpoint. Four colorectal cancer patients (15% of the total study cohort) had objective response. The only serious adverse event was a transient colitis, which appeared in 1 of the 2 patients given PD-1 inhibitor with complete response. Apart from those two, overall survival was similar for patients who did and did not receive study treatment.Conclusions: The systematic MetAction approach may point forward to a refined framework for how to interpret the complexity of sensitivity versus resistance and patient safety that resides in tumor sequence data, for the possibly improved outcome of precision cancer medicine in future studies. ClinicalTrials.gov, identifier: NCT02142036.

p38 MAPK activation through B7-H3-mediated DUSP10 repression promotes chemoresistance

Immunoregulatory protein B7-H3 is involved in the oncogenic and metastatic potential of cancer cells, as well as in drug resistance. Resistance to conventional chemotherapy is an important aspect of melanoma treatment, and a better understanding of how B7-H3 enhances drug resistance may lead to the development of more effective therapies. We investigated the in vitro and in vivo sensitivity of chemotherapeutic agents dacarbazine (DTIC) and cisplatin in sensitive and drug resistant melanoma cells with knockdown expression of B7-H3. We found that knockdown of B7-H3 increased in vitro and in vivo sensitivity of melanoma cells to the chemotherapeutic agents dacarbazine (DTIC) and cisplatin, in parallel with a decrease in p38 MAPK phosphorylation. Importantly, in B7-H3 knockdown cells we observed an increase in the expression of dual-specific MAP kinase phosphatase (MKP) DUSP10, a MKP known to dephosphorylate and inactivate p38 MAPK. DUSP10 knockdown by siRNA resulted in a reversion of the increased DTIC-sensitivity seen in B7-H3 knockdown cells. Our findings highlight the potential therapeutic benefit of combining chemotherapy with B7-H3 inhibition, and indicate that B7-H3 mediated chemoresistance in melanoma cells is driven through a mechanism involving DUSP10-mediated inactivation of p38 MAPK.

Abstract A101: The MetAction trial: long-lasting responses to molecularly matched therapy in end-stage cancer

Background: The first phase of the MetAction trial established the required diagnostic infrastructure, implemented security-approved systems for handling of sensitive information, educated the Trial Team within the context of tumor boards, and estimated costs of the initiative within public health services. The endeavor enabled expedited and safe mutation profiling of metastatic tumors in order to offer molecularly matched medication for end-stage cancer (Ree et al., ESMO Open 2017;2:e000158). The aim of the second trial phase was to investigate the utility of the MetAction pipeline in clinical practice. Procedures: An eligible patient with end-stage metastatic disease from any origin had been on the previous line of systemic therapy for 6 or more weeks with radiologic evaluation intervals of 6-12 weeks and disease progression according to the Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1. Biopsy-sampled metastatic tissue was analyzed by DNA sequencing (Ion Oncomine™ Comprehensive Panel), where called variants were filtered prior to assessment and prioritization, supplemented with fluorescence in situ hybridization to cover relevant biomarkers. The Molecular Tumor Board interpreted the findings within the likelihood of signaling pathway activity, for the sequential Clinical Tumor Board to conclude on potential systemic tumor-directed medication. On study therapy, radiologic work-up was performed every 8 weeks. The primary objective was to compare progression-free survival (PFS) on study treatment, termed Period-B, with PFS for the most recent therapy, termed Period-A. If Period-B/Period-A was ≥1.3, the study therapy was deemed to be of benefit. The incidence of diagnostic adverse events and treatment-related grade 3-5 Common Terminology Criteria for Adverse Events (CTCAE) toxicities was secondary end points. Results: 26 patients were enrolled. Biopsy procedures were undertaken at lung or pleural sites (6 cases), liver or peritoneal sites (19 cases), and an inguinal lymph node (1 case), and did not cause adverse events. Histologic entities were 18 adenocarcinomas (AC), 2 undifferentiated carcinomas, 1 case each of cholangiocarcinoma and squamous cell carcinoma, and 4 different sarcoma entities. 13 patients were found eligible for off-label use of molecularly matched therapy (inhibitor of ALK-, BRAF-, EGFR-, FGFR-, mTOR-, PARP-, ROS1-, or PD-1-mediated signaling). Among the 10 individuals who received study treatment until radiologic evaluation, 5 met the primary end point. The patient with cholangiocarcinoma and a patient with rectal AC primaries, both given crizotinib, obtained Period-B/Period-A outcome slightly better than 1.3. Notably, 3 patients with colon AC primaries, receiving either a combination of panitumumab with vemurafenib or chemotherapy or single-agent pembrolizumab, obtained long-lasting responses. In addition, 1 colon AC patient receiving pembrolizumab with RECIST progression (i.e., primary end point failure) before a long-lasting response to off-protocol continuation, reported CTCAE grade 3 toxicity (a colitis event that immediately resolved on high-dose prednisolone). Conclusion: MetAction procedures and treatments were safe. 15% (4/26) of patients with progressing end-stage cancer had the disease course substantially reversed by this biomarker-directed therapy approach.

Citation Format: Anne Hansen Ree, Kjersti Flatmark, Vigdis Nygaard, Daniel Heinrich, Kjetil Boye, Svein Dueland, Vegard Nygaard, Eivind Hovig, Klaus Beiske, Marius Lund-Iversen, Vivi A. Flørenes, Christin Johansen, Inger Riise Bergheim, Menaka Sathermugathevan, Sigve Nakken, Gry A. Geitvik, Ole C. Lingjærde, Anne-Lise Børresen-Dale, Hege G. Russnes, Gunhild M. Mælandsmo. The MetAction trial: long-lasting responses to molecularly matched therapy in end-stage cancer [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A101.

The MetAction project: Biomarker-directed molecularly matched therapy for end-stage cancer implemented in clinical practice

e14033

Background: The MetAction project consists of two clinical trial phases. The completed first phase established the required diagnostic infrastructure, implemented security-approved systems for handling of sensitive information, educated the entire project staff within the context of tumor boards, and estimated costs of the initiative within public health services. The endeavor enabled expedite and safe mutation profiling of metastatic tumors in order to offer biomarker-based treatment with molecularly matched medication to patients with end-stage cancer, as reported in Ree et al., ESMO Open 2017. The ongoing second trial phase investigates the feasibility of the established MetAction pipeline in clinical practice. Methods: An eligible patient has end-stage metastatic disease from a solid cancer. Metastatic tissue is analyzed by DNA sequencing (Ion Oncomine™ Comprehensive Panel), where called variants are filtered prior to assessment and prioritization, supplemented with fluorescence in situ hybridization to cover relevant biomarkers. The Molecular Tumor Board interprets the findings within the likelihood of signaling pathway activity, and the sequential Clinical Tumor Board (CTB) may conclude on treatment with any systemic tumor-directed medication. Results: At the time of writing, 19 patients enrolled onto the second trial phase have accomplished the diagnostic procedures from sampling of metastatic tissue to CTB conclusion. Biopsy procedures were undertaken at lung or pleural sites (five cases), liver or superficial or deep peritoneal sites (13 cases), and an inguinal lymph node (one case) and did not cause adverse events. Histologic entities were 12 adenocarcinomas and one case each of squamous cell and undifferentiated carcinoma, cholangiocarcinoma, and four different sarcoma entities. Twelve patients have been found eligible for off-label use of molecularly matched therapy (inhibitor of ALK-, BRAF-, EGFR-, FGFR-, mTOR-, PARP-, or PD-1-mediated signaling). Conclusions: We will report on patient outcome (progression-free survival, overall response rate, and tolerance) to this biomarker-directed treatment in end-stage cancer. Clinical trial information: NCT02142036.

Ets-1 transcription factor is widely expressed in benign and malignant melanocytes and its expression has no significant association with prognosis

Ets-1 transcription factor has been associated with tumor progression in various carcinomas, but its expression in malignant melanoma was only recently described. The study was conducted in two steps: exploratory and confirmatory. In the first step, we studied 69 primary melanomas, 28 metastatic melanomas, 10 usual intradermal nevi and 13 various melanocytic skin lesions. In the second step, an additional group of 98 patients with follow-up of up to 200 months was also evaluated. Immunohistochemical analysis of formalin-fixed/paraffin-embedded tissues was performed using 1G11 antibody and polymer conjugate for visualization. While Ets-1 was variably expressed in 83% primary melanomas in exploratory and 69% in the confirmatory group, the expression of Ets-1 was also found in normal benign melanocytes and all nevi. Analysis of the exploratory group revealed lower expression of Ets-1 in primary melanomas than in common nevi (P=0.048, Mann-Whitney U-test) and metastatic melanomas expressed significantly less Ets-1 than primary melanomas (P=0.015, Mann-Whitney U-test). There was a negative correlation between Ets-1 expression and the largest dimension of the primary tumors (r=0.23, P=0.034, Spearman's correlation rank test), but no correlation with the depth of tumor invasion (Breslow thickness) or the presence of ulceration was found. Analyses of the confirmatory group revealed no association between Ets-1 expression with disease-specific survival or time to treatment failure. However, a statistical trend was found for worse outcome for those primary melanomas that had strong expression (H-score >100) of Ets-1 (P=0.054). Ets-1 is expressed in benign melanocytes probably due to their neural crest origin. We conclude that Ets-1 expression cannot be used to differentiate between benign and malignant melanocytic lesions and it has no definite association with clinical outcome. At the same time, its role in tumor progression in some cases of malignant melanoma cannot be entirely excluded.

Expression of S100A4 combined with reduced E-cadherin expression predicts patient outcome in malignant melanoma

The aim of the present study was to analyze the expression of S100A4 and E-cadherin in a panel of primary and metastatic malignant melanoma, and to correlate the expression level to clinicopathological parameters. The expression of S100A4 was examined by immunohistochemistry in 99 superficial spreading and 60 nodular primary melanomas, while the expression of E-cadherin was analyzed in 92 superficial spreading and 52 nodular lesions from the same panel. The expression levels of S100A4 and E-cadherin in the biopsies were inversely correlated, with S100A4 being expressed at the highest frequency in the nodular and E-cadherin in the superficial spreading lesions, respectively. When analyzing the melanoma subgroups separately, it was revealed that expression of S100A4 had a more significant impact on patient outcome in early superficial spreading melanomas than in the nodular subtype, while E-cadherin expression did not predict patient outcome in any of the subgroups. When examining all the patients, both markers give clinical information as predictors for disease-free survival, but when combining the expression of the two markers, a stronger significant correlation between high E-cadherin expressing/S100A4 negative biopsies and increased disease-free survival (P=0.002) was revealed, demonstrating the importance of examining the expression of more than one factor involved in the metastatic cascade when predicting patient outcome. We have also evaluated the relationship between the expression of these two antigens and cell cycle and signal transduction factors.

COX-2 expression in striated muscle under physiological conditions

OBJECTIVES

The role of cyclooxygenase-2 (COX-2) in disease has been extensively studied, (Annu Rev Med (2002) 53:35; N Engl J Med (2001) 345:433) but less information is available with respect to possible physiological functions of COX-2. Information on how and where COX-2 is expressed under physiological conditions may increase our understanding of its physiological role. Previous studies have revealed a COX-2 dependent production of prostanoids under physiological conditions, without entirely determining the source of this production.

MATERIALS AND METHODS

To assess COX-2 expression under normal conditions, we analyzed tissue specimens that were removed from 30 healthy study subjects in conjunction with surgical procedure related to insertion of dental implants and from three patients which had muscle tissue from Quadriceps femoris muscle removed as part of surgical treatment of soft tissue sarcomas not directly affecting the muscle tissue. Immunohistochemistry and immunoblotting (Western blotting) was used to assess the presence of COX-2 protein.

RESULTS

In 25 of 30 patients (83%), COX-2 protein was expressed in striated muscle, as assessed by immunohistochemistry. All cases had COX-2 expression verified by Western blotting. In none of the 25 subjects with COX-2 expression did we notice concomitant inflammation of the adjacent submucosal tissue.

CONCLUSIONS

It is a novel finding that COX-2 is expressed in striated muscle under physiological conditions. COX-2 activity in striated muscle is a possible explanation for the hitherto unknown localization of prostanoids synthesis under physiological conditions.

Clinical and cell line specific expression profiles of a human gene identified in experimental central nervous system metastases

Some cancers, particularly malignant melanomas and carcinomas of the breast and lung, metastasize to the central nervous system (CNS) in advanced stages. In order to develop into clinically manifest metastases, hematogenously disseminated tumor cells must respond to trophic factors within the CNS microenvironment. We have previously identified a nuclearfactor, com1, expressed in human breast carcinoma cells upon formation of experimental metastatic tumors in the CNS. In the present study distinct com1 mRNA expression was detected in cerebral metastases from patients with lung carcinomas, whereas the expression level was generally much lower in glioblastomas (primary brain tumors). In tissue specimens from normal brain and lung, as well as in glioma and lung carcinoma cell lines, com1 expression was barely detectable. One potential mechanism involved in the induction of com1 expression was indicated in the metastatic MCF7/LCC2 breast carcinoma cells. Significant increases in the level of com1 mRNA were observed upon activation of receptor tyrosine kinase signaling, which is known to operate during metastatic tumor cell proliferation within the CNS. The observations in this study strengthen the assumption that com1 may be involved in the tumor cell response to regulatory signals upon metastasis formation.

Cyclin A expression in superficial spreading malignant melanomas correlates with clinical outcome

The present study analysed by immunohistochemistry the protein level of cyclin A and Ki-67 in a panel of paraffin-embedded tissue obtained from 172 primary (110 superficial and 62 nodular) and 73 metastatic melanomas, and ten benign naevi. Since cyclin A exists in the same quaternary complex in the S-phase of the cell cycle as the cdk inhibitor p21WAF1/CIP1, the levels of the two proteins were compared. Cyclin A and Ki-67 were heterogeneously expressed in the malignant tumours, whereas in benign naevi, only rare positive cells were detected. In superficial spreading melanomas, the cyclin A level was related to tumour thickness, with less expression in thinner lesions (p<0.00001), and to Ki-67 (p<0.00001) and p21WAF1/CIP1 (p=0.01) scores. Multivariate analysis showed that in addition to the depth of the primary tumour, the protein level of cyclin A was an independent indicator of relapse-free period (thickness, p<0.00001; cyclin A, p=0.0003). In contrast, in nodular melanoma, the cyclin A level was associated with Ki-67 expression, but neither cyclin A nor Ki-67 was related to tumour thickness (cyclin A, p=0.06; Ki-67, p=0.61) and neither had any impact on relapse-free (cyclin A, p=0.64; Ki-67, p=0.32) or overall (cyclinA, p=0.94; Ki-67, p=0.45) survival. In conclusion, the results indicate that cyclin A is a strong prognostic factor for patients with superficial spreading melanomas. In nodular melanomas, the proliferation rate seems to have little impact on disease progression.

Expression of cell cycle proteins in ovarian carcinoma cells in serous effusions-biological and prognostic implications

OBJECTIVE

The aim of this study was to investigate the expression of cell cycle proteins in ovarian carcinoma cells in serous effusions and respective solid tumors.

METHODS

Fifty-five malignant effusions and 38 tumors (20 primary, 18 metastatic) were immunohistochemically stained for cyclin A, p27(kip1), and Ki-67. Staining extent (0-100% cells) and intensity (0-3 scale) were scored. Cyclin A and p27(kip1) expression was additionally studied in 29 malignant effusions using immunoblotting. Immunohistochemistry results in effusions were evaluated for possible association with clinicopathologic parameters.

RESULTS

Nuclear immunoreactivity for all markers was detected on carcinoma cells in the majority of effusions using immunohistochemistry. Similarly, immunoblotting showed the presence of cyclin A and p27(kip1) in 29/29 and 25/29 specimens, respectively. Intense (3) immunoreactivity for Ki-67 was detected more often in peritoneal effusions, compared with those of pleural location (P = 0.036). Staining in primary and metastatic lesions was generally comparable to that of tumor cells in effusions. Staining for p27(kip1) was more diffuse in effusion specimens obtained prior to the institution of chemotherapy (P = 0.042). In an analysis of all effusions, an association was observed between the number of cells that were immunoreactive for Ki-67, cyclin A, and p27(kip1) (cyclin A-Ki-67: P = 0.008; p27(kip1)-Ki-67: P = 0.019; cyclin A-p27(kip1): P = 0.032). In survival analysis, the presence of more diffuse (P = 0.042) and intense (P = 0.019) staining for cyclin A correlated with prolonged overall survival.

CONCLUSIONS

The expression of the studied cell cycle markers does not differ markedly between ovarian carcinoma cells in the pleural and peritoneal cavity, supporting our previous studies of several metastasis-associated molecules. The presence of cyclin-A-positive cell populations is associated with a more favorable disease outcome, possibly due to the targeting of proliferating cells by chemotherapeutic agents. However, the decline in the fraction of p27(kip1)-positive cells in posttreatment specimens may point to additional mechanisms involved in this selection.

Amplification and overexpression of PRUNE in human sarcomas and breast carcinomas-a possible mechanism for altering the nm23-H1 activity

PRUNE, the human homologue of the Drosophila gene, is located in 1q21.3, a region highly amplified in human sarcomas, malignant tumours of mesenchymal origin. Prune protein interacts with the metastasis suppressor nm23-H1, but shows impaired affinity towards the nm23-H1 S120G mutant associated with advanced neuroblastoma. Based on these observations, we previously suggested that prune may act as a negative regulator of nm23-H1 activity. We found amplification of PRUNE in aggressive sarcoma subtypes, such as leiomyosarcomas and malignant fibrous histiocytomas (MFH) as well as in the less malignant liposarcomas. PRUNE amplification was generally accompanied by high mRNA and moderate to high protein levels. The sarcoma samples expressed nm23-H1 mostly at low or moderate levels, whereas mRNA and protein levels were moderate to high in breast carcinomas. For the more aggressive sarcoma subtypes, 9/13 patients with PRUNE amplification developed metastases. A similar situation was observed in all breast carcinomas with amplification of PRUNE. Infection of NIH3T3 cells with a PRUNE recombinant retrovirus increased cell proliferation. Possibly, amplification and overexpression of PRUNE has the same effect in the tumours. We suggest that amplification and overexpression of PRUNE could be a mechanism for inhibition of nm23-H1 activity that affect the development or progression of these tumours.

Reduced expression of p21WAF1 is an indicator of malignant behaviour in anal carcinomas

AIMS

p21 and p27 protein expression were examined in a comparatively large series of patients with squamous cell carcinoma of the anal canal and compared with clinical and histopathological data (tumour stage, nodal status and differentiation).

METHODS AND RESULTS

We analysed the expression of p21 and p27 protein in 94 anal carcinomas by immunohistochemistry. Nuclear p21 and p27 staining were detected in 71% (67/94) and 75% (71/94) of the cases, respectively. There was no significant association between p27 staining and tumour stage, nodal status or overall survival. We observed that negative p21 immunoreactivity was significantly associated with poorly differentiated anal carcinomas. Furthermore, a shorter overall survival for patients with no p21 protein expression was seen.

CONCLUSIONS

Our data indicate that p21 levels, but not p27 expression, may be a useful predictor of survival in patients with anal carcinomas.

Levels of cyclin D1 and D3 in malignant melanoma: deregulated cyclin D3 expression is associated with poor clinical outcome in superficial melanoma

We examined 172 primary (110 superficial and 62 nodular) and 73 metastatic melanomas, as well as 10 benign nevi, for protein expression of cyclin D1 and cyclin D3 and evaluated the relationship between deregulated protein levels and clinical outcome. For both proteins, a heterogeneous nuclear staining pattern was observed. Cyclin D3 was expressed by 96% of primary and 97% of metastatic melanomas. The corresponding percentages for cyclin D1 were 62% and 29%, respectively. In benign nevi, only rare cyclin D3-positive cells and no cyclin D1-positive cells were observed. High levels of cyclin D3 (>5% of the cells stained) were detected in 26 of 62 (42%) nodular melanomas and in 22 of 110 (20%) superficial tumors, whereas no such difference was observed with respect to cyclin D1. In superficial melanomas, a significant concordant staining pattern was observed between cyclin D1 and cyclin D3 (P = 0.0009), cyclin D1 and Ki-67 (P = 0.0001), cyclin D1 and cyclin A (P = 0.02), cyclin D3 and Ki-67 (P < 0.00001), and cyclin D3 and cyclin A (P = 0.002). Kaplan-Meier analysis revealed that high levels of cyclin D3 were an indicator of early relapse and decreased overall survival for patients with superficial (P = 0.001 and P = 0.009, respectively) but not nodular (P = 0.64 and P = 0.23) melanoma. Cyclin D1 did not have any impact on disease-free and overall survival for either of the subtypes. In conclusion, our results suggest that deregulation of cyclin D3 expression leading to increased proliferation may be a prognostic factor for superficial melanoma, whereas deregulated cell cycle machinery seems to have little impact on disease progression of nodular melanoma.

Interleukin-6 dependent induction of the cyclin dependent kinase inhibitor p21WAF1/CIP1 is lost during progression of human malignant melanoma

Human melanoma cell lines derived from early stage primary tumors are particularly sensitive to growth arrest induced by interleukin-6 (IL-6). This response is lost in cell lines derived from advanced lesions, a phenomenon which may contribute to tumor aggressiveness. We sought to determine whether resistance to growth inhibition by IL-6 can be explained by oncogenic alterations in cell cycle regulators or relevant components of intracellular signaling. Our results show that IL-6 treatment of early stage melanoma cell lines caused G1 arrest, which could not be explained by changes in levels of G1 cyclins (D1, E), cdks (cdk4, cdk2) or by loss of cyclin/cdk complex formation. Instead, IL-6 caused a marked induction of the cdk inhibitor p21WAF1/CIP1 in three different IL-6 sensitive cell lines, two of which also showed a marked accumulation of the cdk inhibitor p27Kip1. In contrast, IL-6 failed to induce p21WAF1/CIP1 transcript and did not increase p21WAF1/CIP1 or p27kip1 proteins in any of the resistant lines. In fact, of five IL-6 resistant cell lines, only two expressed detectable levels of p21WAF1/CIP1 mRNA and protein, while in three other lines, p21WAF1/CIP1 was undetectable. IL-6 dependent upregulation of p21WAF1/CIP1 was associated with binding of both STAT3 and STAT1 to the p21WAF1/CIP1 promoter. Surprisingly, however, IL-6 stimulated STAT binding to this promoter in both sensitive and resistant cell lines (with one exception), suggesting that gross deregulation of this event is not the unifying cause of the defect in p21WAF1/CIP1 induction in IL-6 resistant cells. In somatic cell hybrids of IL-6 sensitive and resistant cell lines, the resistant phenotype was dominant and IL-6 failed to induce p21WAF1/CIP1. Thus, our results suggest that in early stage human melanoma cells, IL-6 induced growth inhibition involves induction of p21WAF1/CIP1 which is lost in the course of tumor progression presumably as a result of a dominant oncogenic event.

E-Cadherin-dependent growth suppression is mediated by the cyclin-dependent kinase inhibitor p27(KIP1)

Recent studies have demonstrated the importance of E-cadherin, a homophilic cell-cell adhesion molecule, in contact inhibition of growth of normal epithelial cells. Many tumor cells also maintain strong intercellular adhesion, and are growth-inhibited by cell- cell contact, especially when grown in three-dimensional culture. To determine if E-cadherin could mediate contact-dependent growth inhibition of nonadherent EMT/6 mouse mammary carcinoma cells that lack E-cadherin, we transfected these cells with an exogenous E-cadherin expression vector. E-cadherin expression in EMT/6 cells resulted in tighter adhesion of multicellular spheroids and a reduced proliferative fraction in three-dimensional culture. In addition to increased cell-cell adhesion, E-cadherin expression also resulted in dephosphorylation of the retinoblastoma protein, an increase in the level of the cyclin-dependent kinase inhibitor p27(kip1) and a late reduction in cyclin D1 protein. Tightly adherent spheroids also showed increased levels of p27 bound to the cyclin E-cdk2 complex, and a reduction in cyclin E-cdk2 activity. Exposure to E-cadherin-neutralizing antibodies in three-dimensional culture simultaneously prevented adhesion and stimulated proliferation of E-cadherin transfectants as well as a panel of human colon, breast, and lung carcinoma cell lines that express functional E-cadherin. To test the importance of p27 in E-cadherin-dependent growth inhibition, we engineered E-cadherin-positive cells to express inducible p27. By forcing expression of p27 levels similar to those observed in aggregated cells, the stimulatory effect of E-cadherin-neutralizing antibodies on proliferation could be inhibited. This study demonstrates that E-cadherin, classically described as an invasion suppressor, is also a major growth suppressor, and its ability to inhibit proliferation involves upregulation of the cyclin-dependent kinase inhibitor p27.

Protein expression of the cell-cycle inhibitor p27Kip1 in malignant melanoma: inverse correlation with disease-free survival

In the present study we analyzed, by immunohistochemistry, a panel of human melanomas for protein expression of the cyclin-dependent kinase (cdk) inhibitor p27Kip1 and evaluated whether deregulated expression correlates with clinical outcome for this type of cancer. We found that p27Kip1 was strongly expressed by normal melanocytes and benign nevi, whereas in malignant melanoma, a heterogeneous expression pattern was observed. In the case of nodular melanomas, the level of p27Kip1 was found to correlate significantly with the thickness of the tumor, with less protein expressed in thicker lesions. We also found that patients having tumors with fewer than 5% p27Kip1-staining cells had a significantly higher risk of early relapse of their disease compared with those expressing moderate or high levels. In contrast, the level of p27Kip1 did not correlate with tumor thickness or disease-free survival in patients with superficial spreading melanomas, suggesting that p27Kip1 may play different roles in these two major pathological subgroups of malignant melanoma. Furthermore, p27Kip1 did not appear to have an influence on overall survival for either subgroup. When we examined the combined effect of p21WAF1/CIP1 (another cdk inhibitor) and p27Kip1 on clinical outcome, we found that analysis of these two cdk inhibitors together may have greater prognostic potential than either alone. In conclusion, our results suggest that virtually complete loss of p27Kip1 protein expression has potential importance as a prognostic indicator of early relapse in patients with nodular melanoma The results, furthermore, underscore the value of analyzing multiple cell cycle regulatory proteins to obtain the most reliable indication of prognosis.

Differential expression patterns of S100A2, S100A4 and S100A6 during progression of human malignant melanoma

Three members of the S100 gene family, S100A2, S100A4 and S100A6, have been suggested to be associated with cancer development and metastasis. To study their involvement in the tumorigenesis of human melanoma, we examined the mRNA expression levels of the 3 genes in 45 melanoma metastases and in 20 benign nevi. Interestingly, whereas none of the metastases expressed S100A2 mRNA, and the expression level was low in 6 cell lines established from primary melanomas, all nevi showed moderate to high expression levels. Our results suggest that loss of S100A2 gene expression may be an early event in melanoma development. A significant correlation was found between the expression of S100A6 in melanoma metastases and both the survival time of the patients and the thickness of the corresponding primary tumors. For the S100A4 gene, however, no relationship was found between gene expression and clinical parameters of melanoma malignancy. The observed differences in expression patterns of the 3 S100 genes suggest distinct roles of their products in melanoma tumorigenesis and/or metastasis, and the results encourage studies to evaluate the potential value of using S100A2 and S100A6 expression levels as markers in the clinical management of melanoma.

Expression of stromelysin-3 in medullary carcinoma of the breast

Matrix metalloproteinases are belived to play a central role in the invasion and metastasis of human cancers by mediating the degration of extracellular matrix components. Expression of stromelysin-3 (ST3), a new member of matrix metalloproteinase family, was investigated by in situ hybridization in 32 tissue samples of medullary carcinoma of the breast. Eighty-four per cent of the cases showed ST3 gene expression in stromal cells adjacent to tumor cells. Therefore, expression of ST3 in stromal cells may be expected to play a significant role in the destruction of extracellular matrix and invasion of medullary carcinoma of the breast.

Differential expression patterns of S100A2, S100A4 and S100A6 during progression of human malignant melanoma

Three members of the S100 gene family, S100A2, S100A4 and S100A6, have been suggested to be associated with cancer development and metastasis. To study their involvement in the tumorigenesis of human melanoma, we examined the mRNA expression levels of the 3 genes in 45 melanoma metastases and in 20 benign nevi. Interestingly, whereas none of the metastases expressed S100A2 mRNA, and the expression level was low in 6 cell lines established from primary melanomas, all nevi showed moderate to high expression levels. Our results suggest that loss of S100A2 gene expression may be an early event in melanoma development. A significant correlation was found between the expression of S100A6 in melanoma metastases and both the survival time of the patients and the thickness of the corresponding primary tumors. For the S100A4 gene, however, no relationship was found between gene expression and clinical parameters of melanoma malignancy. The observed differences in expression patterns of the 3 S100 genes suggest distinct roles of their products in melanoma tumorigenesis and/or metastasis, and the results encourage studies to evaluate the potential value of using S100A2 and S100A6 expression levels as markers in the clinical management of melanoma.

Loss of expression of receptor tyrosine kinase family genes PTK7 and SEK in metastatic melanoma

Protein tyrosine kinases (PTKs) have been implicated in the development of many common human tumours including melanoma. Previously we isolated PTK gene sequences expressed in normal melanocytes. Here we examined expression of 9 of these genes in cell lines derived from defined stages of melanoma progression, by Northern blotting and in some cases immunoblotting. We also tested cells from 2 animal models of particular stages in progression, as well as uncultured biopsies of metastatic melanoma. The expression of 2 receptor kinase family members found in melanocytes, PTK7/CCK-4 and SEK/TYRO1, was decreased or lost in advanced melanomas. PTK7 mRNA was found in only 54% of melanoma cell lines and 20% of melanoma biopsies. Similarly, expression was lost in 2 advanced cell lines selected from an early melanoma line that did express PTK7 mRNA. SEK/TYRO1 expression was observed in 75% and 17% of cell lines from primary and metastastic melanomas, respectively. Conversely, mRNA for the non-receptor kinase PTK6/BRK was not detected in normal melanocytes or primary melanoma lines, but was found in 9% of metastatic melanoma cell lines.

TGF-beta mediated G1 arrest in a human melanoma cell line lacking p15INK4B: evidence for cooperation between p21Cip1/WAF1 and p27Kip1

We have studied TGF-beta mediated G1 arrest in WM35, an early stage human melanoma cell line. These cells have lost p15INK4B expression through loss of one chromosome 9 and rearrangement of the other. In asynchronously growing WM35, TGF-beta caused reductions in cyclin D1, cyclin A and cdk4 proteins and their associated kinase activities and an increase in both p21Cip1/WAF1 and p27Kip1. These findings were confirmed in cells released from quiescence in the presence of TGF-beta, in which TGF-beta inhibited or delayed the reduction in the cdk inhibitors that normally occurs in late G1. In contrast to observations in other cell types, there was an increased association of both p21Cip1/WAF1 and p27Kip1 with cyclin D1/cdk4 and with cyclin E/cdk2 during TGF-beta mediated arrest of asynchronously growing cells. Upregulation of p21Cip1/WAF1 preceded that of p27Kip1. Furthermore, p21Cip1/WAF1 and p27Kip1 were not present in the same cdk complexes but bound distinct populations of target cdk molecules. Both p21Cip1/WAF1 and p27Kip1 immunoprecipitates from asynchronously growing cells contained active kinase complexes. These KIP-associated kinase activities were reduced in TGF-beta arrested cells. It has been proposed that in TGF-beta arrested epithelial cells, up-regulation of p15INK4B and of p15INK4B binding to cdk4 serves to destabilize the association of p27Kip1 with cyclin D1/cdk4, promoting p27Kip1 binding and inhibition of cyclin E/cdk2. Our findings demonstrate that this is not a universal mechanism of G1 arrest by TGF-beta. In TGF-beta arrested WM35, which lack p15INK4B, the increased p21Cip1/WAF1 may serve a similar function to that of p15INK4B: initiating kinase inhibition and providing an additional mechanism to supplement the effect of p27Kip1 on G1 cyclin/cdks.

Cyclin kinase inhibitor p21WAF1/CIP1 in malignant melanoma: reduced expression in metastatic lesions

Immunohistochemical analysis of the expression of the cyclin kinase inhibitor p21WAF1/CIP1 in a panel of primary and metastatic human melanocytic tumors was performed. It was found that, independent of the p53 status, approximately 30% of the primary melanomas and 40% of the metastases completely lacked expression of this cell cycle inhibitor. Some tumors were also analyzed by Northern blotting, and in most of the cases a consistant correlation between mRNA and protein expression was observed. In four benign nevi studied, WAF1/CIP1 mRNA was expressed whereas the protein was not detected, suggesting a post-transcriptional regulation of the inhibitor in these cases. In superficial spreading melanomas, a significant correlation between protein expression and tumor thickness was found, with thin lesions showing low protein levels. Interestingly, by comparing primary and metastatic specimens obtained from the same patient, a reduction in p21WAF1/CIP1 antibody staining was observed in the latter, probably reflecting a more aggressive phenotype of the metastases. In conclusion, our results demonstrate the complexity in the relationship between p21WAF1/CIP1 expression and tumor phenotype and furthermore suggest that aberrant expression of the cyclin-dependent kinase inhibitor may be of importance in the development and progression of sporadic malignant melanoma.

Reversal of the in vivo metastatic phenotype of human tumor cells by an anti-CAPL (mts1) ribozyme

The putative role of the CAPL gene in enhancing the development of human cancer metastasis was examined by transfecting human high-expressing osteosarcoma cells with a hammerhead ribozyme directed against the gene transcript. The ability of the ribozyme to cleave target mRNA in intact cells was demonstrated in a 5'-rapid amplification of cDNA ends assay. In transfected cells, a suppression of the capacity to give skeletal metastases upon intracardial injection into nude rats was observed in cell clones with reduced expression of CAPL mRNA and protein, whereas in vitro and in vivo cell proliferation and tumorigenicity were unchanged. The results provide direct evidence that the expression level of the CAPL-encoded protein can determine the metastatic potential of osteosarcoma cells, and they demonstrate an association between reduced gene expression and proliferation-independent inhibition of the metastatic capacity of human tumor cells. The effects of the specific cleavage of CAPL mRNA indicate that the gene product is involved in key cellular functions associated with the metastatic process and suggest that therapeutic modulation of the protein function may represent a novel approach for inhibiting the metastatic spread of cancer cells.

Impact of the cyclin-dependent kinase inhibitor p27Kip1 on resistance of tumor cells to anticancer agents

A low proliferating fraction in solid tumors limits the effectiveness of cell cycle-dependent chemotherapeutic agents. To understand the molecular basis of such "kinetic" resistance we cultured tumor cells as multicellular spheroids and examined levels of p27Kip1, a cyclin-dependent kinase inhibitor known to be upregulated by intercellular contact in normal cells. When transferred from monolayer to three-dimensional culture, a consistent upregulation (up to 15-fold) of p27 protein was observed in a panel of mouse and human carcinoma cell lines. Antisense-oligonucleotide-mediated downregulation of p27 in EMT-6 mammary tumor cell spheroids reduced intercellular adhesion, increased cell proliferation, sensitized tumor cells to 4-hydroperoxycyclophosphamide, and restored drug- or radiation-induced cell-cycle perturbations repressed in spheroid culture. Our results implicate p27 as a regulator of drug resistance in solid tumors and suggest that tumor-targeted p27 antagonists may be useful chemosensitizers in conjunction with conventional anticancer therapy.

Involvement of the pRb/p16/cdk4/cyclin D1 pathway in the tumorigenesis of sporadic malignant melanomas

Biopsies from 61 sporadic metastatic malignant melanomas and five melanoma cell lines were examined for homozygous deletions and mutations in the CDKN2 gene (p16). As the p16 protein is involved in a cell cycle regulatory pathway consisting of at least pRb, cdk4 and cyclin D1, the tumours were also screened for amplifications of the last two genes. Moreover, the transcript levels of the genes were determined and the results compared with the immunohistochemically assessed expression of pRb. Altogether, homozygous deletions of CDKN2 were found in seven tumours (11%) and two of five cell lines, whereas a mutation was detected in only one biopsy, indicating that in sporadic melanomas the former mechanism is predominant for inactivating this gene. Notably, in total 59% of the metastatic lesions lacked detectable expression of p16 mRNA, whereas all the biopsies were found to express pRb. In accordance with the postulated negative feedback loop between p16 and pRb, one melanoma cell line showed overexpression of CDKN2 mRNA together with very low levels of the Rb protein. Amplification of the other two genes may not be important in the tumorigenesis of melanomas, as only one CDK4 and no CCND1 amplification was observed. However, highly elevated CDK4 mRNA levels, compared with that seen in a panel of normal tissues, were observed in 76% of the tumours, accompanied in 71% of the cases by high expression of the CCND1 cyclin activator. Although a low frequency of CDKN2 DNA aberrations was observed, the high number of tumours that lacked CDKN2 expression but showed overexpression of CDK4 and/or CCND1, suggest that functional inactivation of pRb through this pathway may be involved in the development or progression of sporadic human melanomas.

Homozygous deletion frequency and expression levels of the CDKN2 gene in human sarcomas--relationship to amplification and mRNA levels of CDK4 and CCND1

Homozygous deletions of the putative tumour-suppressor gene CDKN2, which encodes an inhibitor of cdk4, have been detected in a high percentage of cancer cell lines of various histological types. In the present study, 109 human sarcomas were examined for homozygous deletions and for mRNA expression levels of the CDKN2 gene. Altogether, deletions were found in only eight (7%) of the cases, but, interestingly, in two (of eight) malignant Schwannomas and in two (of five) rhabdomyosarcomas. In comparison, such deletions were seen in only one (of 21) osteosarcomas and in none of 20 MFHs and 21 liposarcomas. Notably, highly elevated CDKN2 mRNA levels were found in 33% of the sarcomas, whereas no detectable transcript was present in 12 normal tissues. Amplifications of CDK4 and CCND1 (cyclin D1) were observed in 11% and 4% of the sarcomas respectively, but never in tumours with CDKN2 deletions. The level of CDK4 mRNA expression was increased in nine tumours in addition to the 12 samples with CDK4 amplification. Increased levels of the cyclin D1 transcript was found in 37 cases, four with and 33 without amplification. The data indicate that aberrations of these functionally related genes, or in regulation of the expression of the kinase, the activator or the inhibitor, may participate in sarcoma development. Furthermore, the data suggest that homozygous CDKN2 deletions may be of dissimilar significance in different sarcoma subtypes.

Accumulation of p53 protein in human malignant melanoma. Relationship to clinical outcome

Paraffin-embedded tissue from the primary tumours of 116 patients with malignant melanoma, and in 40 cases also from corresponding metastases, were examined for accumulation of p53 protein. The fraction of tumours with positive p53 immunostaining was 13% in the least invasive and 36% in the most invasive primary lesions and 48% in the metastases. Where comparisons could be made, both the level and pattern of p53 immunoreactivity were the same in the primary and metastatic tumours. Nine (50%) patients with p53-positive and 34 (39%) with p53-negative primaries relapsed during the first 5 years, but no difference in disease-free period was observed between the two groups. However, an overall longer survival time was observed among patients with p53-positive primaries, especially for those with tumours less invasive than 3.0 mm. Notably, all 11 patients in this group were alive 5 years after diagnosis of the disease, whereas 15 out of 70 (21%) patients with p53-negative tumours died in same period. The results show that an increased level of p53 protein does not indicate increased degree of malignancy in melanoma, but rather suggests a more favourable disease progression.

In vitro and in vivo variation in transferrin receptor expression on a human medulloblastoma cell line

The poor prognosis associated with pediatric central nervous system tumors such as medulloblastoma has led to the development and investigation of a variety of new treatment techniques. Therapeutic agents include targeted-toxin conjugates or immunotoxins that show significant in vitro activity against many brain tumors. Transferrin receptors (TRs) are specific, cell-surface antigens that are expressed preferentially on brain tumors rather than on normal human brain tissue. This antigen has been successfully targeted in human and nonhuman brain tumors in vitro and in vivo. In this study, when TRs were used as a target in the DAOY human medulloblastoma-derived cell line in vitro, a significant level of expression was confirmed by testing the sensitivity to different immunotoxins. To ensure the relevance of the in vitro data to the in vivo situation, we also analyzed TR expression in DAOY tumors growing in athymic mice and rats. Immunocytochemistry, immunohistochemistry, immunobead binding, immunofluorescence, 125iodine-transferrin binding, and Northern blot analysis were used to compare TR expression in DAOY cells in vitro and in vivo. All in vitro assays demonstrated significant TR expression, whereas in vivo, the TR expression was negligible in the DAOY tissue. The results caution against extrapolating in vitro antigen and receptor expression data directly to the in vivo situation. Using a transferrin-toxin conjugate in a nude rat model of leptomeningeal carcinomatosis, we achieved therapeutic efficacy, despite demonstrating reduced TR expression on tumor tissue. With respect to clinical efficacy, the reduced expression of TR on DAOY medulloblastoma in vivo may be less significant than expected because of the extreme potency of immunotoxins observed in central nervous system tumors.

The protooncogene CHOP/GADD153, involved in growth arrest and DNA damage response, is amplified in a subset of human sarcomas

The C/EBP-homologous transcription factor CHOP (GADD153) is inducible by growth inhibition or DNA damage, and has been shown to be oncogenically activated by the specific (12;16) translocation in human myxoid liposarcoma. We have now found CHOP amplification in two sarcoma cell lines with previously reported amplification of the nearby GLI gene. Among 98 other human sarcomas of various types, CHOP was amplified in a hemangiopericytoma, a liposarcoma, and two osteosarcoma. High constitutive expression levels of CHOP were observed in tumors with gene amplification, but also in some other samples. The nearby MDM2 gene, which codes for a protein that may inactivate wild-type p53, has previously been reported to be frequently amplified in sarcoma. In our sarcoma panel, MDM2 was amplified in 9 cases. MDM2 and CHOP were co-amplified in two of these, whereas the two osteosarcomas had amplified CHOP but not MDM2. CHOP was amplified in both cell lines with GLI amplification, and MDM2 only in one. No mutations in the TP53 gene have been found in samples with amplification of MDM2. In contrast, the cell line in which CHOP but not MDM2 was amplified had mutated TP53, suggesting that selection of this amplicon was not mediated through p53 inactivation.

MDM2 gene amplification and transcript levels in human sarcomas: relationship to TP53 gene status

BACKGROUND

Alterations of the TP53 tumor suppressor gene appear to be implicated in the tumorigenesis and progression of several types of human cancer, including different histologic subtypes of sarcomas. The MDM2 (murine double minute-2) gene encodes a nuclear phosphoprotein that may interact with both mutant and wild-type p53 proteins, thereby inhibiting p53-mediated transactivation in a dose-dependent manner. Recently it has been suggested that mdm2 and p53 proteins are components of an autoregulatory loop in which the MDM2 gene is transactivated by p53.

PURPOSE

Our purpose was to examine the frequency of MDM2 amplifications in larger panels of sarcomas, determine if the mRNA level could be elevated in tumors without concomitant gene amplification, and relate MDM2 findings to the TP53 status of the tumors.

METHODS

Sarcoma tissue of different histologic subtypes was obtained from 68 patients at the time of surgery and from 26 human xenografts in nude mice. In addition, two human sarcoma cell lines (OSA and U2OS) were studied. Genomic DNA from tumor tissue, in vitro cell lines, and peripheral blood cells were isolated by Southern-blot analysis methods to determine MDM2 gene amplification. Tumor DNA was analyzed for possible TP53 gene mutations in exons 5, 7, and 8 by constant denaturing gel electrophoresis. To determine the MDM2 and TP53 mRNA levels, Northern-blot analysis was performed.

RESULTS

Amplification of the MDM2 gene was detected in 10 tumors (10.3%). Whereas MDM2 amplification and/or over-expression were found only in two (U2OS and OSA cell lines) of 18 osteosarcomas, one of 20 malignant fibrous histiocytomas (MFHs), and in none of 14 leiomyosarcomas, such alterations were observed in two of two fibrosarcomas, three of six malignant schwannomas, three of 19 liposarcomas, and in the one hemangiopericytoma examined. MDM2 overexpression was found in all nine examined cases with and in three tumors without amplification. TP53 mutations were detected in 12 cases (five osteosarcomas, four MFHs, and three leiomyosarcomas), of which none showed amplification, but one had increased levels of MDM2 mRNA. None of the fibrosarcomas, malignant schwannomas, and liposarcomas examined had mutated TP53. The six sarcomas that showed high TP53 mRNA expression in the absence of gene mutation also had elevated levels of MDM2 mRNA.

CONCLUSIONS

The present data provide further indications that increased MDM2 expression level, caused by gene amplification or altered regulation of transcription, is involved in tumor progression of some, but not all, sarcoma subtypes.

TP53 allele loss, mutations and expression in malignant melanoma

p53 alterations at the DNA, mRNA and protein levels were studied in tumour metastases sampled from 30 patients with malignant melanoma. Paraffin-embedded sections from these and an additional 12 patients were examined for the presence of p53 protein. TP53 gene aberrations were found in 7 of 30 (23%) of the patients, six of which showed loss of heterozygosity (LOH). Point mutations were detected in only two cases, one of which had LOH whereas the other was non-informative. Increased levels of p53 mRNA were present in only one tumour with, but in six cases without, detectable DNA abnormalities. Four of the latter and six tumours with normal transcript levels had immunohistochemically detectable levels of p53 protein. In 25 cases in which corresponding primary and metastatic lesions could be compared, closely similar immunoreactivity patterns were observed. Increased expression of the MDM2 gene was found in only one tumour in parallel with overexpression of p53. Altogether, the data indicate that inactivation of the p53 regulatory pathway is not of major significance in the tumorigenesis of malignant melanoma. However, a significant association was found between p53 immunoreactivity and the relapse-free period in patients with superficial spreading melanoma. That increased protein expression was predominantly found in tumours without DNA alterations might suggest a role for the wild-type p53 protein in restricting malignant cell proliferation in these cases.

Expression of the neuroectodermal intermediate filament nestin in human melanomas

Nestin is a newly identified intermediate filament expressed in proliferating neuronal progenitor cells, but not in the adult brain. Nestin expression reappears in many tumors of the central nervous system and has in human glioblastomas been associated with a high degree of malignancy. Because melanocytes are of neuroectodermal origin, we studied nestin expression in benign and malignant cells of the melanocytic lineage using Northern blot and immunohistochemical analyses. Nestin mRNA was detected in 24 of 34 metastatic melanomas and in 1 of 4 benign nevi, whereas the protein was expressed in 10 of 15 primary melanomas, in 29 of 34 metastatic tumors, and in 3 of 4 nevi. Neither normal melanocytes nor any of 4 basal cell carcinomas showed detectable levels of the protein. The high fraction of melanocytic tumors which express nestin, particularly the metastatic melanomas, suggests that nestin may be a useful marker for such malignancies. Furthermore, although no significant correlation between nestin expression and tumor malignancy was observed, the protein was most abundantly expressed in the infiltrating part of the tumors, indicating a possible involvement of nestin in tumor invasion.

Mapping of amplification units in the q13-14 region of chromosome 12 in human sarcomas: some amplica do not include MDM2

Amplification of cellular oncogenes may be important for the development and progression of malignant tumors. In human sarcomas, amplification of several genes located to the q13-14 region of chromosome 12 has been reported. Because the mdm2 protein seems to inactivate the tumor suppressor protein p53, a selective growth advantage of 12q13-14 amplification has previously been assigned to increased copy number and expression of the MDM2 gene. We have analyzed a panel of 98 human sarcomas of different subtypes to characterize the 12q13-14 amplica and determine which of the genes GLI, A2MR, SAS, MDM2, and GADD153 (CHOP) in this region was most consistently amplified. MDM2 was amplified in 9 of the tumors, SAS in 10, GADD153 in 4, GLI in 2, and A2MR in 2. Amplification was, in most cases, associated with increased expression of the corresponding gene. SAS and MDM2 were coamplified in 8 of the tumors, whereas GADD153, GLI, and A2MR were only amplified together with SAS. One liposarcoma showed amplification of MDM2 alone, whereas two osteosarcomas and a rhabdomyosarcoma cell line showed amplification of SAS and GADD153 (CHOP) but not MDM2. It is suggested that the selective target for these amplica may be an as yet unidentified gene localized between SAS and MDM2.

p53 abnormalities in different subtypes of human sarcomas

In this report we examined p53 alterations at the DNA, mRNA, and protein levels on tissue from 39 patients with different subtypes of sarcoma. Loss of heterozygosity for the chromosome 17p region was found in 60, 63, and 33% of 10 informative osteosarcomas, 11 malignant fibrous histiocytomas, and 6 leiomyosarcomas, respectively. In addition, 2 of 10 tumors belonging to a heterogeneous group of soft tissue sarcomas showed loss of heterozygosity. Elevated levels of p53 mRNA were found in six tumors, four had a truncated transcript, and in six patients no mRNA was detected. In most cases, elevated transcript levels were accompanied by overexpression of protein as studied by immunohistochemistry, whereas the presence of truncated transcripts was associated with negative immunostaining. Point mutations in exons 5, 7, or 8 of the TP53 gene were detected in seven tumors. Six of these expressed high levels of mRNA and protein, probably reflecting a point mutation in one of the alleles and loss of the other. Three of the mutations have not previously been described. Taken together, p53 abnormalities were found in approximately 65% of the osteosarcomas, malignant fibrous histiocytomas, and leiomyosarcomas examined and in 30% of the other soft tissue tumors. The results indicate that the TP53 gene is involved in the tumorigenesis of several sarcoma subtypes in a higher fraction of cases than was previously recognized.

Levels of nm23 messenger RNA in metastatic malignant melanomas: inverse correlation to disease progression

Data obtained in experimental murine tumors and in clinical specimens of human breast cancer have suggested that the nm23 gene may function as a metastasis suppressor gene. In this report we examined the nm23 mRNA level in tumor tissue obtained from distant metastases in 33 patients with malignant melanoma. The gene was differentially expressed in the tumors with a 20-fold range in hybridization intensities. The levels of nm23 mRNA in benign nevi obtained from 12 of the 33 patients were relatively low, with a mean value of 17% of that in the melanomas. In attempts to relate the level of nm23 expression in the tumor metastases to progression of the disease, the time from biopsy of the primary tumor to the appearance of metastases was used as a clinical end point. It was found that patients developing metastases during the first 2 years after diagnosis had significantly lower levels of tumor nm23 expression (56% of the mean value) compared to patients with less aggressive disease (164%) (P < 0.0004). In concordance with previous data the association found here between low levels of nm23 mRNA and the malignant potential of melanomas suggests that the nm23 gene may be implicated in the mechanism of disease progression in some types of human cancer.