Targeting RCC1 to block the human soft-tissue sarcoma by disrupting nucleo-cytoplasmic trafficking of Skp2

Soft-tissue sarcomas (STS) emerges as formidable challenges in clinics due to the complex genetic heterogeneity, high rates of local recurrence and metastasis. Exploring specific targets and biomarkers would benefit the prognosis and treatment of STS. Here, we identified RCC1, a guanine-nucleotide exchange factor for Ran, as an oncogene and a potential intervention target in STS. Bioinformatics analysis indicated that RCC1 is highly expressed and correlated with poor prognosis in STS. Functional studies showed that RCC1 knockdown significantly inhibited the cell cycle transition, proliferation and migration of STS cells in vitro, and the growth of STS xenografts in mice. Mechanistically, we identified Skp2 as a downstream target of RCC1 in STS. Loss of RCC1 substantially diminished Skp2 abundance by compromising its protein stability, resulting in the upregulation of p27Kip1 and G1/S transition arrest. Specifically, RCC1 might facilitate the nucleo-cytoplasmic trafficking of Skp2 via direct interaction. As a result, the cytoplasmic retention of Skp2 would further protect it from ubiquitination and degradation. Notably, recovery of Skp2 expression largely reversed the phenotypes induced by RCC1 knockdown in STS cells. Collectively, this study unveils a novel RCC1-Skp2-p27Kip1 axis in STS oncogenesis, which holds promise for improving prognosis and treatment of this formidable malignancy.

Rb and p53-Deficient Myxofibrosarcoma and Undifferentiated Pleomorphic Sarcoma Require Skp2 for Survival

Myxofibrosarcoma (MFS) and undifferentiated pleomorphic sarcoma (UPS) are highly genetically complex soft tissue sarcomas. Up to 50% of patients develop distant metastases, but current systemic therapies have limited efficacy. MFS and UPS have recently been shown to commonly harbor copy number alterations or mutations in the tumor suppressor genes RB1 and TP53. As these alterations have been shown to engender dependence on the oncogenic protein Skp2 for survival of transformed cells in mouse models, we sought to examine its function and potential as a therapeutic target in MFS/UPS. Comparative genomic hybridization and next-generation sequencing confirmed that a significant fraction of MFS and UPS patient samples (n = 94) harbor chromosomal deletions and/or loss-of-function mutations in RB1 and TP53 (88% carry alterations in at least one gene; 60% carry alterations in both). Tissue microarray analysis identified a correlation between absent Rb and p53 expression and positive expression of Skp2. Downregulation of Skp2 or treatment with the Skp2-specific inhibitor C1 revealed that Skp2 drives proliferation of patient-derived MFS/UPS cell lines deficient in both Rb and p53 by degrading p21 and p27. Inhibition of Skp2 using the neddylation-activating enzyme inhibitor pevonedistat decreased growth of Rb/p53-negative patient-derived cell lines and mouse xenografts. These results demonstrate that loss of both Rb and p53 renders MFS and UPS dependent on Skp2, which can be therapeutically exploited and could provide the basis for promising novel systemic therapies for MFS and UPS. SIGNIFICANCE: Loss of both Rb and p53 renders myxofibrosarcoma and undifferentiated pleomorphic sarcoma dependent on Skp2, which could provide the basis for promising novel systemic therapies.See related commentary by Lambert and Jones, p. 2437.

Cell cycle and apoptosis regulatory proteins, proliferative markers, cell signaling molecules, CD209, and decorin immunoreactivity in low-grade myxofibrosarcoma and myxoma

The histologic differential diagnosis between intramuscular myxoma and low-grade myxofibrosarcoma can be quite difficult in some cases. To identify a diagnostic immunohistochemical marker, we compared the staining profiles of 19 different antigens, including cell cycle proteins, apoptosis proteins, and proliferative markers, and selected other signaling and structural proteins in these two tumors. Ten cases each of intramuscular myxoma and low-grade myxofibrosarcoma were stained with antibodies directed against apoptosis regulatory proteins (Bcl2, activated caspase-3, phospho-H2A.X, and cleaved PARP), cell cycle regulatory proteins (Rb1, Cyclin-A, CDKN1B, and Cdt1), proliferative markers (KI67, MCM2, phospho-histone H3, and geminin), cell signalling molecules (c-Myc, EGF, EGFR, PLA2G4A, and HSP90), a dendritic cell marker (CD209), and the extracellular matrix proteoglycan decorin. Staining patterns of myxoma and myxofibrosarcoma were compared using Fisher's exact test and the Mann-Whitney test. For each potential diagnostic marker studied, the proportions of cases scored as positive on both dichotomous or ordinal scales were not significantly different between myxoma and myxofibrosarcoma. Myxoma and myxofibrosarcoma share a common immunophenotype for each of the markers studied. Distinction between these tumors is still predominantly based on morphologic criteria.

Clinical aggressiveness of myxofibrosarcomas associates with down-regulation of p12CDK2AP1: prognostic implication of a putative tumor suppressor that induces cell cycle arrest and apoptosis via mitochondrial pathway

BACKGROUND

Attenuated endogenous protein levels of cyclin-dependent kinase 2 associated protein 1 (p12(CDK2AP1)) and its active homodimer p25(CDK2AP1) were found in myxofibrosarcoma-derived cell lines. Clinical and biological significances of this putative tumor suppressor in myxofibrosarcoma were studied.

METHODS

Plasmids carrying the CDK2AP1 gene and small hairpin RNA interference (shRNAi) targeting CDK2AP1 were transfected into NMFH-1 and/or OH931 cells to evaluate the effects on the CDK2, active caspase 3 (CASP3), cleaved-CASP8 and -CASP9 levels, cell cycle regulation, and/or apoptotic responses. Immunostaining of p12(CDK2AP1) was interpretable in 102 primary myxofibrosarcomas and correlated with clinicopathological variables, CDK2, Ki-67 and active CASP3 protein levels, and disease-specific survival.

RESULTS

Exogenous expression of p12(CDK2AP1) in NMFH-1 and OH931 cells significantly induced G0/G1 cell cycle arrest and down-regulated CDK2 protein level. In NMFH-1 cells, these aspects were reversed by shRNAi targeting CDK2AP1 gene. Increased active CASP3 and cleaved-CASP9, but not -CASP8, were detected after CDK2AP1 overexpression, suggesting the cellular apoptosis were induced through the mitochondrial pathway. Immunostains of p12(CDK2AP1) were aberrantly decreased in 56.9 % of cases; positively and negatively correlated with protein levels of CDK2 (p = 0.023), Ki-67 (p = 0.001) and active CASP3 (p < 0.001), respectively. Following by high histological grades, p12(CDK2AP1) down-regulation was predictive of worse disease-specific survival in univariate (p = 0.003) and multivariate (p = 0.004) analyses.

CONCLUSIONS

Through down-regulation of CDK2, high p12(CDK2AP1) level induced cell cycle arrest and the mitochondrial-dependent apoptotic pathway. Low p12(CDK2AP1) level represents a poor prognostic factor in patients with myxofibrosarcoma.

The novel myxofibrosarcoma cell line MUG-Myx1 expresses a tumourigenic stem-like cell population with high aldehyde dehydrogenase 1 activity

BACKGROUND

Myxofibrosarcoma comprises a spectrum of malignant neoplasms withprominent myxoid stromata, cellular pleomorphism, and distinct curvilinear vascular patterns. These neoplasms mainly affect patients in the sixth to eighth decades of life and the overall 5-year survival rate is 60-70%.

METHODS

After the establishment of the novel myxofibrosarcoma cell lines MUG-Myx1, cells were characterized using short tandem repeat (STR), copy number variation (CNV), and genotype/loss-of-heterozygosity (LOH) analyses. The growth behaviour of the cells was analyzed with the xCELLigence system and an MTS assay. The tumourigenicity of MUG-Myx1 was proved in NOD/SCID mice. Additionally, a stem-like cell population with high enzymatic activity of aldehyde dehydrogenase 1 (ALDH1(high)) was isolated for the first time from myxofibrosarcoma cells using the Aldefluor® assay followed by FACS analysis.

RESULTS

The frozen primary parental tumour tissue and the MUG-Myx1 cell line showed the same STR profile at the markers D3S1358, TH01, D21S11, D18S51, Penta E, D5S818, D13S317, D7S820, D16S539, CSF1PO, Penta D, Amelogenin, D8S1179, TPOX, and FGY. Typically, myxofibrosarcoma gain and/or amplification was mapped to 7p21.3-q31.1, q31.1-q31.33, q33-q36.2, p21.3, p21.2, p14.1-q11.23, q31.33-q33, p21.2-p14.1, q11.23-q21.3, q36.2-q36.3, which, respectively are known to harbour tumour-associated genes, including TIF, BRAF, MLL3, SMO, and MET. Typically an LOH for myxofibrosarcoma on chr5 q21 was found. In addition, MUG-Myx1 ALDH1(high) cells showed an upregulation of the ABC transporter ABCB1 and ABCG2; higher c-Myc, E-cadherin and SOX-2 expression; and a higher potential for tumourigenicity and proliferation levels.

CONCLUSION

The new myxofibrosarcoma cell line MUG-Myx1 was established to enrich the bank of publicly available cell lines, with respect to providing comprehensive genetic and epigenetic characterization. Furthermore, because of their tumourigenicity, the cell line is also suitable for in vivo experiments.

Prognostic impact of Skp2, ER and PGR in male and female patients with soft tissue sarcomas

Background

S-phase kinase-associated protein 2 (Skp2) is a member of mammalian F-box proteins. The purpose of this study is to clarify the prognostic significance of expression of Skp2 related to gender, estrogen receptor (ER) and progesterone receptor (PGR) in soft tissue sarcomas (STS). Skp2 has been demonstrated to display an oncogenic function since its overexpression has been observed in many human cancers. Optimized treatment of STS requires better identification of high-risk patients who will benefit from adjuvant therapy. The prognostic significance of Skp2 related to ER and PGR in STS has not been sufficiently investigated.

Methods

Tissue microarrays from 193 STS patients were constructed from duplicate cores of viable and representative neoplastic tumor areas. Immunohistochemistry was used to evaluate the expression of Skp2, ER and PGR.

Results

In univariate analyses, high tumor expression of Skp2 correlated (p = 0.050) with reduced disease-specific survival (DSS). In subgroup analyses expression of PGR in males (p = 0.010) and in patients older than 60 years (p = 0.043) were negative prognostic factors for DSS. Expression of ER in females was a positive prognostic factor for DSS (p = 0.041). In co-expression analyses in the whole cohort, low expression of Skp2 in combination with low expression of ER was positive for DSS (p = 0.049). In females high expression of Skp2 in combination with low expression of ER was a negative prognosticator (p = 0.021). In the multivariate analyses, age (p = 0.012), malignancy grade (p < 0.001), wide resection margins (P = 0.010), ER negative / PGR positive co-expression profile (p = 0.002) and ER positive / PGR negative co-expression profile (p = 0.015) were independent negative prognostic factors for DSS. In females expression of Skp2 (p = 0.006) was associated with shorter DSS.

Conclusions

We found diverse prognostic impacts of expression of Skp2, ER, PGR and DSS in male and female patients with STS. In men, but not women, ER positive / PGR negative co-expression profile was an independent negative prognostic factor for DSS. In women, but not men, high expression of Skp2 was associated with reduced DSS.

Prognostic impact of Jab1, p16, p21, p62, Ki67 and Skp2 in soft tissue sarcomas

PURPOSE

The purpose of this study is to clarify the prognostic significance of expression of Jab1, p16, p21, p62, Ki67 and Skp2 in soft tissue sarcomas (STS). Optimised treatment of STS requires better identification of high risk patients who will benefit from adjuvant therapy. The prognostic significance of Jab1, p16, p21, p62, Ki67 and Skp2 in STS has not been sufficiently investigated.

EXPERIMENTAL DESIGN

Tissue microarrays from 193 STS patients were constructed from duplicate cores of viable and representative neoplastic tumor areas. Immunohistochemistry was used to evaluate the expression of Jab1, p16, p21, p62, Ki67 and Skp2.

RESULTS

In univariate analyses, high tumor expression of Ki67 (P = 0.007) and Skp2 (P = 0.050) correlated with shorter disease-specific survival (DSS). In subgroup analysis, a correlation between Skp2 and DSS was seen in patients with malignancy grade 1 or 2 (P = 0.027), tumor size >5 cm (P = 0.018), no radiotherapy given (P = 0.029) and no chemotherapy given (P = 0.017). No such relationship was apparent for Jab1, p16, p21 and p62; but p62 showed a positive correlation to malignancy grade (P = 0.019). Ki67 was strongly positively correlated to malignancy grade (P = 0.001). In multivariate analyses, Skp2 was an independent negative prognostic factor for DSS in women (P = 0.009) and in patients without administered chemotherapy or radiotherapy (P = 0.026).

CONCLUSIONS

Increased expression of Skp2 in patients with soft tissue sarcomas is an independent negative prognostic factor for disease-specific survival in women and in patients not administered chemotherapy or radiotherapy. Besides, further studies are warranted to explore if adjuvant chemotherapy or radiotherapy improve the poor prognosis of STS with high Skp2 expression.

Ploidy and S-phase fraction are correlated with lymphovascular space invasion that is predictive of outcomes in endometrial cancer

BACKGROUND

Pathological detection of lymphovascular space invasion (LVSI) is a useful prognostic marker for patients with endometrial cancer. However, LVSI is criticized for its subjectivity and poor reproducibility. To improve the outcomes of patients with endometrial cancer, we evaluated objective parameters associated with LVSI to generate more accurate LVSI assessments and to identify patients with high-risk disease.

METHODS

We reviewed the medical records of 137 patients with endometrial cancer. Flow cytometry was used to determine DNA ploidy and S-phase fraction. Estrogen and progesterone receptor (ER and PR) levels and p53 and k-ras mutational status were tested.

RESULTS

LVSI was found in 36 patients (26.3%). Patients with LVSI had significantly decreased recurrence-free survival and overall survival compared to those without LVSI. Aneuploid tumors were significantly more frequent in LVSI-positive patients compared with LVSI-negative patients (odds ratio = 5.208, P < 0.001). With the exception of p53 mutational status, there was a statistically significant relationship between LVSI and other parameters tested. However, by multivariate analysis, DNA ploidy and S-phase fraction were significantly correlated with LVSI (P = 0.034 and 0.001, respectively).

CONCLUSION

Ploidy and S-phase fraction correlate with LVSI, which is a significant independent predictor of clinical outcome in patients with endometrial cancer.

Prognostic implication of MET overexpression in myxofibrosarcomas: an integrative array comparative genomic hybridization, real-time quantitative PCR, immunoblotting, and immunohistochemical analysis

It remains obscure in myxofibrosarcoma about the basis of tumorigenesis, progression, and metastasis. Chromosome 7 gains are common in some sarcomas, including myxofibrosarcoma, whereas the specific oncogenes are yet to be characterized. We performed an integrative study of MET gene at 7q31.2 to elucidate its implication in myxofibrosarcoma. Focused on candidate oncogenes on chromosome 7, 385K array comparative genomic hybridization was used to profile DNA copy number alterations of 12 samples. MET transcript was successfully quantified by real-time RT-PCR for 16 laser-microdissected tumors and two myxofibrosarcoma cell lines (NMFH-1, OH931). MET immunoexpression was assessable in 86 primary localized tumors with follow-up. To analyze endogenous MET expression and activation, NMFH-1 and OH931 cells, both with wild-type MET gene, were subjected to Western blotting and hepatocyte growth factor-treated NMFH-1 cells were evaluated for the kinetics of MET tyrosine phosphorylation. Non-random large-scale gains on 7q were detected in five cases, delineating three recurrent amplicons, 7q21.11-7q21.3, 7q22.1-22.3, and 7q31.1-7q32.3, in which the locus of MET displayed increased copy number, among others. MET mRNA was upregulated in OH931, NMFH-1, and nine tumors (56%), whereas neither gene dosage nor mRNA expression of MET was associated with clinicopathological factors. In contrast, MET protein overexpression, present in 67% of cases, was highly related to deep location (P=0.004), higher grades (P=0.001), and more advanced stages (P<0.001). Importantly, MET overexpression independently portended inferior metastasis-free survival (P=0.004) and overall survival (P=0.0221). Expressing activating phospho-MET at Tyr(1234)/Tyr(1235), OH931 cells had more abundant total MET than NMFH-1 cells, whereas the latter became promptly phosphorylated on stimulation of hepatocyte growth factor. In primary myxofibrosarcomas, MET overexpression, as a frequent event, is likely driven by 7q gains with mRNA upregulation, associated with important prognosticators, and independently predictive of worse outcomes, highlighting its possible causative function in tumor aggressiveness and potentiality as a therapeutic target.

Prognostic implication of ezrin overexpression in myxofibrosarcomas

BACKGROUND

The bases of tumorigenesis, progression, and metastasis remain obscure in myxofibrosarcoma. As a member of ezrin-radixin-moesin family, ezrin acts as a link between the cell membrane and actin cytoskeleton to integrate cell adhesion-mediated signaling. It is implicated in tumor progression and metastatic dissemination, and it is associated with adverse outcomes in several cancer types, including pediatric sarcomas.

METHODS

Ezrin immunostain could be assessed from tissue microarrays of 78 cases of primary localized myxofibrosarcomas and correlated with clinicopathological factors and patient survival. In two myxofibrosarcoma cell lines, ezrin mRNA expression was measured by real-time reverse transcriptase-polymerase chain reaction and the endogenous expression and activating phosphorylation of ezrin protein analyzed by Western blot test.

RESULTS

Ezrin overexpression was significantly associated with remarkable tumor necrosis (P = 0.025), increased histological grades (P = 0.037), advanced American Joint Committee on Cancer stages (P = 0.034), and higher mitotic rate (P < 0.001). Importantly, ezrin overexpression independently predicted inferior metastasis-free survival (P = 0.012, risk ratio = 4.083) and disease-specific survival (P = 0.0337, risk ratio = 4.537). The mRNA and total protein of ezrin in various cells were comparable in the expression level. Despite variation in abundance, phosphorylated ezrin at threonine(567) was detectable in myxofibrosarcoma cell lines but not in fibroblasts.

CONCLUSIONS

In primary myxofibrosarcomas, ezrin overexpression correlates with important prognostic elements and independently portends worse outcomes, highlighting the potential prognostic usefulness of ezrin in predicting tumor aggressiveness.