[Downregulation of Herg1 suppresses osteosarcoma proliferation and invasion by targeting Hippo signaling pathway]

Objective: To detect the effect and regulatory mechanism of human ether à go-go related gene 1 (Herg 1) knockdown on the proliferation and invasion of osteosarcoma (OS). Methods: We constructed a recombinant adenovirus vector (Ad5-Herg1-shRNA) expressing short hair RNA (shRNA) against Herg1 and tested the knockdown efficiency. Then, the effects of Herg 1 knockdown on the proliferation, growth and invasion of osteosarcoma were measured by using cell counting kit-8 (CCK-8), wound healing assay, Transwell assay and xenograft model of nude mice, respectively. Tandem affinity purification, mass spectrometry and dual luciferase reporter assay were used to find out the molecules interacted with Herg1. Western blot was used to detect the expressions of large tumor suppressor gene (LATS1), p-LATS1, Yes-associated protein (YAP) and p-YAP in cells after infection of Ad5-Herg1-shRNA. Results: Compared to Ad5-control-shRNA, Ad5-Herg1-shRNA dramatically inhibited the expression of Herg1 in OS cells. The result of CCK8 array demonstrated that 143B cell vitalities of Ad5-Herg1-shRNA1 and Ad5-Herg1-shRNA2 group were (65.47±3.90)% and (79.90±1.52)%, significantly lower than (100.00±6.14)% of Ad5-control-shRNA group. Meanwhile, U2OS cell vitality of Ad5-Herg1-shRNA1 and Ad5-Herg1-shRNA2 group were (69.69±1.36)% and (76.72±2.75)%, significantly lower than (100.00±3.01)% of Ad5-control-shRNA group (all P<0.001). The results of wound healing array showed that 143B cell migration rates of Ad5-Herg1-shRNA1 and Ad5-Herg1-shRNA2 group were (33.03±2.88)% and (36.47±4.16)%, significantly lower than (97.78±2.28)% of Ad5-control-shRNA group. Meanwhile, U2OS cell migration rates of Ad5-Herg1-shRNA1 and Ad5-Herg1-shRNA2 group were (68.07±0.90)% and (73.97±1.25)%, significantly lower than (96.50±1.12)% of Ad5-control-shRNA group (all P<0.001). The results of Transwell showed that 143B cell invasion numbers of Ad5-Herg1-shRNA1 and Ad5-Herg1-shRNA2 group were 36.50±12.15 and 44.83±7.62, significantly lower than 195.33±19.68 of Ad5-control-shRNA group. Meanwhile, U2OS cell migration rates of Ad5-Herg1-shRNA1 and Ad5-Herg1-shRNA2 group were 21.83±7.99 and 22.85±7.08, significantly lower than 83.33±12.36 of Ad5-control-shRNA group (all P<0.001). The results of xenograft model of OS showed that the tumor volume and weight of Ad5-Herg1-shRNA group were significantly smaller than of Ad5-control-shRNA group after 14 days and 5 weeks of inoculation, respectively (P<0.001). Moreover, knockdown of Herg1 inhibited the metastasis of OS cells. In mechanism, Herg1 protein interacted with NF2 protein. Knockdown of Herg1 significantly suppressed the expression levels of LATS1 and YAP protein, and promoted the phosphorylation of LATS1 and YAP in OS cells (all P<0.001). Conclusion: Our findings suggest that Herg1 participates in the proliferation and motility of OS cells and may serve as a potential therapeutic target for osteosarcoma patients.

[Expression of Ether à go-go 1 and its molecular mechanism of regulating the malignant phenotype of osteosarcoma]

Objective: To explore the expression of ether à go-go 1 (Eag1) in human osteosarcoma and its molecular mechanisms of regulating the malignant phenotype of osteosarcoma. Methods: The expression levels of Eag1 in osteosarcoma cell lines and human osteosarcoma tissues were detected by reverse transcription polymerase chain reaction (RT-PCR), western blot analysis and immunohistochemistry. The small interfering RNA (siRNA) was used to inhibit the expression of Eag1. The abilities of proliferation and invasion in osteosarcoma cells transfected with Eag1 siRNA were determined by CCK-8, colony formation assay, transwell assay and wound healing assay. The osteosarcoma xenograft model of nude mouse was established and tumor growth curve was drawn. Western blot analysis was performed to detect the expression of vascular endothelial growth factor (VEGF) and signal transducer and activator of transcription 3 (STAT3) in osteosarcoma cells transfected with Eag1 siRNAs. Results: Eag1 was overexpressed in the osteosarcoma cells and tissues. Compared with the scrambled siRNA group, the cell survival rates of Eag1 siRNA1 and Eag1 siRNA2 groups of the two cell lines were significantly lower. [MG-63 cells: scrambled siRNA group (100.0±4.65)%, Eag1 siRNA1 group (63.57±3.89)%, and Eag1 siRNA2 group (54.13±3.70)%; Saos-2 cells: scrambled siRNA group (100.00±5.46)%, Eag1 siRNA1 group (56.70±5.34)%, and Eag1 siRNA2 group (40.27±5.28)% (P<0.001 for all)]. Similar results were obtained from colony formation assay. The colony formation rates of MG-63 cells: the scrambled siRNA group was (92.00±3.46)%, Eag1 siRNA1 group (60.00±3.06)%, and Eag1 siRNA2 group (53.67±2.40)%; the colony formation rates of Saos-2 cells: the scrambled siRNA group was (92.00±5.57)%, Eag1 siRNA1 group (52.33±5.13)%, and Eag1 siRNA2 group (41.67±2.73)%. Compared with the scrambled siRNA group, P<0.001 for all. The tumor volumes of osteosarcoma xenograft in the Eag1 siRNA1 and Eag1 siRNA2 groups were significantly smaller than that in the scrambled siRNA group after 10 days treatment (P<0.01 for all). The invasion assay data showed that MG-63 and Saos-2 cells transfected with Eag1 siRNAs exhibited the ability of cell invasion, when compared with the cells transfected with scrambled siRNA. (Invasive cell number of MG-63 cells: the scrambled siRNA group was 134.00±3.61, Eag1 siRNA1 group 105.20±2.52, and Eag1 siRNA2 group 91.00±3.01; Invasive cell number of Saos-2 cells: the scrambled siRNA group was 132.30±3.23, Eag1 siRNA1 group 114.30±3.48, and Eag1 siRNA2 group 82.67±6.33. Compared with the scrambled siRNA group, P<0.01 for all. The migration rates were (62.48±1.83)%, (35.98±1.23)% and (32.30±1.20)% in the three groups of MG-63 cells, and (70.15±1.42)%, (41.38±1.34)% and (32.40±1.92)% in the three groups of Saos-2 cells, respectively. Compared with the scrambled siRNA group, P<0.001 for all. Notably, the expression levels of VEGF decreased evidently after Eag1 siRNAs transfection, paralleled with reduction in the expression levels of STAT3. Conclusions: Eag1 may promote osteosarcoma cell proliferation and invasion by targeting STAT3-VEGF pathway and may be a potential therapeutic target for osteosarcoma.

Refined mapping of the region of loss of heterozygosity on the long arm of chromosome 7 in human breast cancer defines the location of a second tumor suppressor gene at 7q22 in the region of the CUTL1 gene

In breast cancer, loss of heterozygosity (LOH) has been described on the long arm of chromosome 7, at band q31, suggesting the presence of a tumor suppressor gene in this region. In this study, we have identified a second region of LOH on 7q, at band 7q22. Deletion of genetic material at 7q22 was found in all tumor types and grades and was associated with increased tumor size. The region of LOH at 7q22 in every case included one or more of three polymorphic markers that are located within the CUTL1 gene. LOH of 7q22 has also been documented in the case of human uterine leiomyomas (Zeng et al., 1997; Ishwad et al., 1997). Interestingly, in both leiomyomas and mammary tumors induced in transgenic mice expressing the Polyomavirus (PyV) large T (LT) antigen, immunocomplexes of CUTL1 and PyV LT antigen were detected (Webster et al., 1998). Altogether, genetic data in human breast cancer and biochemical analyses in breast tumors from transgenic mice suggest that CUTL1 is a candidate tumor suppressor gene.

Loss of heterozygosity and reduced expression of the CUTL1 gene in uterine leiomyomas

Cytogenetic analyses has revealed deletions and/or rearrangments at several chromosomal positions in approximately half of uterine leiomyomas. The most frequent genetic alteration, deletion of 7q22, was found in approximately 35% of studied cases with cytogenetic abnormalities (128/366=35%). The same chromosomal band was also found to be deleted in a fraction of acute myeloid leukemias and myelodysplastic syndromes. The frequent deletion of 7q22 in some tumors suggest that a tumor suppressor gene may be located in this region. The human Cut-like homeobox gene, CUTL1, is one of the genes localized to 7q22 and it was shown previously to encode a transcriptional repressor that down-modulates the expression of c-Myc. Activation of the c-Myc oncogenic potential has been shown in many cancers to result from alterations in one or the other of its several mechanisms of regulation. These observations led us to hypothesize that CUTL1 could act as a tumor suppressor gene. In the present study, we have identified polymorphic markers within and directly adjacent to CUTL1 at 7q22 and demonstrated that these markers are present in a commonly deleted region in seven out of 50 uterine leiomyomas samples examined. Furthermore, Northern blot analysis revealed that CUTL1 mRNA levels were reduced in eight tumors out of 13. These results suggest that CUTL1 may act as a tumor suppressor gene whose inactivation could be of pathological importance in the etiology of uterine leiomyomas.

Plasminogen activator inhibitor 1 messenger RNA expression and molecular evidence for del(7)(q22) in uterine leiomyomas

We analyzed the expression of plasminogen activator inhibitor 1 (PAI-1) in 16 leiomyomas and adjacent myometrium of women who underwent a hysterectomy while in the proliferative (n = 8) and secretory phases (n = 8) of the menstrual cycle. We localized the PAI-1 and its mRNA expression in smooth muscle and vessel endothelial cells of uterine tissues using immunocytochemistry and in situ hybridization. The expression of PAI-1 mRNA was higher in 11 (68.75%) of 16 leiomyomas compared with the adjacent myometrium (leiomyoma/myometrium ratio, 1.4-3.0; mean, 2.045). The leiomyoma:myometrium ratio of PAI-1 mRNA expression did not change during the proliferative (Phase I) and secretory (Phase II) phases of the menstrual cycle. In the remaining five samples, the leiomyoma:myometrium ratio of PAI-1 mRNA expression was close to 1 (0.8-1.2; mean, 0.92). Because the locus of the PAI-1 gene is on chromosome 7q22, we screened for loss of heterozygosity (LOH) in these samples using the PAI-1 marker and D7S471, an anonymous marker 12 cM telomeric to PAI-1. Four of five samples with low leiomyoma:myometrium ratio had LOH for the PAI-1 and/or D7S471 markers. The fifth sample demonstrated a noninformative analysis for these markers but had LOH for the D7S515, D7S666, and D7S518 markers, all centromeric to PAI-1. Because del(7)(q22), associated with a relatively low PAI-1 mRNA expression, can deregulate matrix proteinases and growth factors' activity in leiomyomas, it is conceivable that del(7)(q22) results in heterogeneous leiomyoma biology.