. Rvs167 interacts with Pho85 cyclins and is implicated as a target of Pho85 kinases in vivo. Our results identify a connection between Cdks and the actin cytoskeleton; interaction of Rvs167 and Pcl-Pho85 Cdks might contribute to actin cytoskeleton regulation in response to stresses such as starvation.

We did not identify any correlation between MDR1 mRNA expression and disease progression in patients with osteosarcoma. It is likely that alterations in other genes are involved in resistance to chemotherapy in osteosarcoma and that they play a more critical role than MDR1 in this disease.

A number of genes are implicated in the initiation and progression of osteosarcoma; however, cytogenetic and comparative genomic hybridization studies indicate the involvement of additional unidentified genes. An examination of gene expression profiles in 22 high-grade osteosarcoma tumor specimens from 15 patients (including paired primary and metastatic samples from five patients) indicated that von Willebrand factor (vWF) mRNA expression may increase during tumor progression. vWF, a large glycoprotein previously considered to be expressed exclusively by endothelial cells and megakaryocytes, is involved in platelet aggregation and adhesion to the subendothelial matrix, processes critical to hematogenous tumor cell metastasis to the lung. Analysis of paired primary and metastatic osteosarcoma tumor samples from 10 patients revealed an increase in vWF gene expression in metastases (P ¼ 0.005). Immunohistochemistry showed that, in addition to the endothelial cells, vWF protein was also detected in osteosarcoma cells in vivo in 13 of 29 tumor specimens as well as in SAOS2, an osteosarcoma cell line. The tumor cell staining correlated positively with high vWF expression in the sample (P ¼ 0.006). Although vascular endothelial cells contribute to the vWF mRNA detected in the tumor samples, there was neither any correlation between vascular density (VD) and vWF mRNA expression nor between VD and clinical outcome. These findings suggest that vWF expression is deregulated in osteosarcoma tumors, potentially contributing to metastasis.

We have examined the in vivo requirement of two recently identified nonessential components of the budding yeast anaphase-promoting complex, Swm1p and Mnd2p, as well as that of the previously identified subunit Apc9p. swm1⌬ mutants exhibit synthetic lethality or conditional synthetic lethality with other APC/C subunits and regulators, whereas mnd2⌬ mutants are less sensitive to perturbation of the APC/C. swm1⌬ mutants, but not mnd2⌬ mutants, exhibit defects in APC/C substrate turnover, both during the mitotic cell cycle and in ␣-factor-arrested cells. In contrast, apc9⌬ mutants exhibit only minor defects in substrate degradation in ␣-factor-arrested cells. In cycling cells, degradation of Clb2p, but not Pds1p or Clb5p, is delayed in apc9⌬. Our findings suggest that Swm1p is required for full catalytic activity of the APC/C, whereas the requirement of Mnd2p for APC/C function appears to be negligible under standard laboratory conditions. Furthermore, the role of Apc9p in APC/C-dependent ubiquitination may be limited to the proteolysis of a select number of substrates.

In order to increase our understanding of the molecular events underlying osteosarcoma progression, the expression of approximately 950 genes was examined in 24 primary and metastatic osteosarcoma tumor specimens. A gene, RMO1, was isolated with decreased expression in metastatic samples. Real-Time PCR corroborated this pattern, revealing lower expression in the primary sample in 6 of 7 cases for which both primary and metastatic osteosarcoma samples were available from the same patient (p ‫؍‬ 0.034). RMO1 is located at 2q33, a region of frequent loss of heterozygosity in cancer, and exhibited loss of heterozygosity in 6 out of 9 primary osteosarcoma tumor samples (67%). Loss of heterozygosity is evident in primary tumors while the decrease in gene expression is seen in the metastatic samples, indicating that these 2 events are separately implicated in cancer progression. Cloning of RMO1 revealed an open reading frame with multiple splice forms with significant homology to GRB7, 10 and 14 and MIG10 in the region containing a Pleckstrin homology domain and a Ras association domain, suggestive of a role in cell signaling and migration. Northern blot analysis indicated that RMO1 mRNA is ubiquitously expressed in tissues except for peripheral blood leukocytes. These data suggest that RMO1 may be a candidate for a protein involved in inhibiting tumor progression. © 2004 Wiley-Liss, Inc. Key words: osteosarcoma; metastasis; RMO1; mRNA expression; loss of heterozygosity A number of genes have been shown to play a role in the pathogenesis of osteosarcoma, including the tumor suppressor genes p53 and Rb, and the proto-oncogenes CDK4 and MDM2. [1][2][3] However, cytogenetic and comparative genomic hybridization studies indicate that additional genes are also involved in the initiation and progression of this disease. 1,4 Osteosarcomas have many complex chromosomal alterations including translocations, deletions and amplifications. Whereas the tumor suppressor genes Rb and p53 are likely to be the targets of the frequent deletions at 13q and 17p in osteosarcoma, the genes associated with allelic loss at regions such as 2q, 5q, 6q, 8p, 9, 10, and 18q remain unknown. 1,4 -9 Deletion at 2q33 is commonly observed in cervical carcinoma, oral squamous cell carcinoma, head and neck squamous cell carcinoma, esophageal squamous cell carcinoma, neuroblastoma and lung cancer, suggesting that the target of this deletion is involved in the development of numerous types of cancer. 10 -15 Inactivation of tumor suppressor genes and activation of oncogenes can lead to their altered expression. For example, decreased gene expression of the tumor suppressor gene BRCA1 correlates with loss of heterozygosity (LOH) and the expression of the protooncogene CDK4 is significantly higher in samples with gene amplification. 3,16,17 The isolation of tumor suppressor genes and oncogenes can therefore be accomplished through a comparison of mRNA expression between tumor samples at different stages of development, such as primary tumor and metastase...