A cytoskeleton-associated protein, TMAP/CKAP2, is involved in the proliferation of human foreskin fibroblasts

Human CKAP2L shows a cell cycle-dependent expression pattern and exhibits microtubule-stabilizing properties

Cytoskeleton-associated protein 2-like (CKAP2L) is a paralogue of cytoskeleton-associated protein 2 (CKAP2). We characterized the expression pattern, subcellular localization, and microtubule-stabilizing properties of human CKAP2L. The levels of both CKAP2L transcript and protein were cell cycle phase-dependent, peaking during the G2/M phase and relatively high in certain human tissues, including testis, intestine, and spleen. CKAP2L protein was detectable in all human cancer cell lines we tested. CKAP2L localized to the mitotic spindle apparatus during mitosis, as reported previously. During interphase, however, CKAP2L localized mainly to the nucleus. Ectopic overexpression of CKAP2L resulted in 'microtubule bundling', and, consequently, an elevated CKAP2L level led to prolonged mitosis. These findings support the mitotic role of CKAP2L during the human cell cycle.

Knockdown of CKAP2 Inhibits Proliferation, Migration, and Aggregate Formation in Aggressive Breast Cancer

Simple Summary

Cancer is a complex disease where cells grow and divide in an uncontrolled manner. It is well established that its development and progression involve major alterations in the activity of mitotic regulators. In order to improve our understanding of the contribution of cell-cycle progression defects to the development of disease, the aim of this study is to identify genes relevant to the proper progression of mitosis that are deregulated in breast cancer. Our findings identified CKAP2 as an important mitotic regulator in BC tumors. Moreover, in vitro experiments showed that gene silencing of CKAP2 blocked cell growth, cell migration, and formation of cell aggregates. These results demonstrated the important role of CKAP2 in breast cancer tumor formation.

Abstract

Loss of mitotic regulation is commonly observed in cancer and is a major cause of whole-chromosome aneuploidy. The identification of genes that play a role in the proper progression of mitosis can help us to understand the development and evolution of this disease. Here, we generated a list of proteins implicated in mitosis that we used to probe a patient-derived breast cancer (BC) continuum gene-expression dataset generated by our group by human transcriptome analysis of breast lesions of varying aggressiveness (from normal to invasive). We identified cytoskeleton-associated protein 2 (CKAP2) as an important mitotic regulator in invasive BC. The results showed that CKAP2 is overexpressed in invasive BC tumors when compared with normal tissues, and highly expressed in all BC subtypes. Higher expression of CKAP2 is also related to a worse prognosis in overall survival and relapse-free survival in estrogen receptor (ER)-positive and human epidermal growth factor receptor type 2 (HER2)-negative BC patients. Knockdown of CKAP2 in SKBR3 cells impaired cell proliferation and cell migration and reduced aggregate formation in a 3D culture. Our results show the important role of CKAP2 in BC tumorigenesis, and its potential utility as a prognostic marker in BC.

CKAP2 overexpression correlates with worse overall survival in patients with lung adenocarcinoma

BACKGROUND

Adenocarcinoma is a non-small-cell lung cancer that is common cancer in both genders, and has poor clinical outcomes. We aimed to evaluate the role of cytoskeleton-associated protein 2 (CKAP2), its prognostic significance, and the relationship between CKAP2 expression and lung adenocarcinoma driver genes.

METHODS

The expression of CKAP2 was studied by immunohistochemical staining of specimens from 88 patients with lung adenocarcinoma. The correlation between clinicopathological features and CKAP2 expression was analyzed. Kaplan-Meier analysis and Cox proportional hazard models were used to examine the prognostic value of CKAP2 in terms of overall survival (OS). The correlation between epidermal growth factor receptor (EGFR) mutation, anaplastic lymphoma kinase (ALK) rearrangement, and CKAP2 expression was analyzed. All histological samples were detected by fluorescence in situ hybridization for EGFR mutations and ALK rearrangements.

RESULTS

Eighty-eight patients with positive CKAP2 expression were observed in this study. Patients with high levels of CKAP2 expression were associated with OS (P = .021). Multivariate Cox regression analysis disclosed that positive CKAP2 expression (P = .043) could independently predict unfavorable OS. In addition, CKAP2 expression was not associated with EGFR mutation (P = .219) and ALK rearrangement (P = .389) in lung adenocarcinoma patients.

CONCLUSION

High expression of CKAP2 may serve as a marker of poor prognosis in lung adenocarcinoma.

Silencing of cytoskeleton-associated protein 2 represses cell proliferation and induces cell cycle arrest and cell apoptosis in osteosarcoma cells

Osteosarcoma is the most common primary bone malignancy, mainly occurring in children and adolescents. Cytoskeleton-associated protein 2 (CKAP2), which plays important roles in cell proliferation, has been reported to be overexpressed in diverse human cancers. In the present study, we aimed at exploring the expression and functions of CKAP2 in osteosarcoma. The mRNA and protein expression of CKAP2 was analyzed on collected osteosarcoma and control bone cyst tissues. The results indicated that CKAP2 expression was remarkably elevated in osteosarcoma tissues compared with bone cysts tissues. The expression level of CKAP2 in osteosarcoma was associated with overall survival, tumor size and tumor stage. In addition, down-regulation of CKAP2 by RNA interference in osteosarcoma cell lines, MG63 and SW1353, caused a remarkable inhibition in cell proliferation in vitro and xenograft growth in nude mice. Silencing of CKAP2 also significantly induced G0/G1 arrest and cell apoptosis of osteosarcoma cells. Furthermore, phosphorylation levels of Janus kinase 2 (JAK2) and Signal transducers and activators of transcription 3 (STAT3) were significantly reduced in CKAP2 knockdown cells. The expression of downstream targets of JAK2/STAT3 signaling, Cyclin D1, Bcl-2 and survivin, was also decreased in CKAP2 knockdown cells. Such aberrations can be rescued by re-expression of RNAi-resistant CKAP2. Collectively, the present study indicates that CKAP2 is a potential oncogene by targeting JAK2/STAT3 signaling, and that CKAP2 may serve as a novel target for osteosarcoma therapy.

CKAP2 (cytoskeleton-associated protein2) is a new prognostic marker in HER2-negative luminal type breast cancer

Background

Recently, we reported cytoskeleton-associated protein2 (CKAP2) as a possible new prognostic breast cancer marker. However, it has not yet been applied in clinic. Therefore, clinical significance of CKAP2 was evaluated in comparison with that of Ki-67 in a cohort of breast cancer patients, and the expression difference was analyzed in cell cycle-arrested cancer and fibroblast cells.

Methods

A total of 579 early breast cancer patients who underwent surgery at the National Cancer Center Hospital in Korea between 2001 and 2005 were accrued. CKAP2-positive cell count (CPCC) and Ki-67 labeling index (Ki-67LI) were evaluated by immunohistochemcal staining. The immunocytochemical staining patterns of CKAP2 and Ki-67 were analyzed in HeLa and human fibroblast cells after synchronization by double thymidine block.

Results

Although there was a significant correlation (R = 0.754, P < 0.001) between CPCC and Ki-67LI, only CPCC was correlated with DFS in overall population (HR, 2.029; 95% CI, 1.012–4.068; P = 0.046) and HER2-negative luminal subgroup (HR, 3.984; 95% CI, 1.350–11.762; P = 0.012) by multivariate analysis. In immunocytochemical staining, more than 50% of serum-starved or non-mitotic cell phase HeLa cells were positive for Ki-67, in comparison to the low CKAP2-positivity, which might explain the prognostic difference between CPCC and Ki-67LI.

Conclusions

The current study showed that CPCC but not Ki-67LI is an independent prognostic indicator in early breast cancer, more specifically in HER2-negative luminal breast cancer. The difference between two markers may be related to the lower background expression of CKAP2 in cancer cells.

CKAP2 phosphorylation by CDK1/cyclinB1 is crucial for maintaining centrosome integrity

Previously, we have reported that CKAP2 is involved in the maintenance of centrosome integrity, thus allowing for proper mitosis in primary hepatocytes. To understand this biological process, we identified the mitosis-specific phosphorylation sites in mouse CKAP2 and investigated CKAP’s possible role in cell cycle progression. Because we observed mouse CKAP2 depletion in amplified centrosomes and aberrant chromosomal segregation, which was rescued by ectopic expression of wild-type CKAP2, we focused on the centrosome duplication process among the various aspects of the cell cycle. Among the identified phosphorylation sites, T603 and possibly S608 were phosphorylated by CDK1–cyclin B1 during mitosis, and the ectopic expression of both T603A and S608A mutants was unable to restore the centrosomal abnormalities in CKAP2-depleted cells. These results indicated that the phosphorylation status of CKAP2 during mitosis is critical for controlling both centrosome biogenesis and bipolar spindle formation.

Involvement of FAK-ERK2 signaling pathway in CKAP2-induced proliferation and motility in cervical carcinoma cell lines

Cervical carcinoma is the fourth most common cause of death in woman, caused by human papillomavirus (HPV) infections and arising from the cervix. Cytoskeleton-associated protein 2 (CKAP2), also known as tumor-associated microtubule-associated protein, has been linked to tumorigenic effects. In the present study, we screened CKAP2 as a new candidate gene which promotes development of cervical carcinoma, in two independent datasets (TCGA and GSE27678). Results showed that CKAP2 expression was significantly up-regulated in cervical cancerous tissues compared with normal counterparts. Gene set enrichment analysis (GSEA) showed that metastasis, cell cycle and FAK pathways were related with elevated CKAP2 expression. Knockdown of CKAP2 expression significantly inhibited cell proliferation, migration and invasion both in HeLa and C-33A cells. And depletion of CKAP2 down-regulated the expression of metastasis and cell cycle related proteins as well as the phosphorylation of ERK2 (p-ERK2), except E-cadherin. In vivo experiment revealed that knockdown of CKAP2 inhibited C-33A cells proliferation. However, FAK inhibitor PF-562271 and ERK2 inhibitor VX-11e treatment significantly inhibited CKAP2 overexpression-induced cell proliferation, migration and invasion in SiHa cells. In conclusion, our study suggests that CKAP2 acts as a functional oncogene in cervical carcinoma development and may exert its function by targeting FAK-ERK2 signaling pathway.

CKAP2 is necessary to ensure the faithful spindle bipolarity in a dividing diploid hepatocyte

Spindle bipolarity is crucial for segregating chromosome during somatic cell division. Previous studies have suggested that cytoskeleton associated protein 2 (CKAP2) is involved in spindle assembly and chromosome segregation. In this study, we show that CKAP2-depleted primary hepatocytes exhibit over-duplicated centrosomes with disjoined chromosomes from metaphase plate. These cells proceed to apoptosis or multipolar cell division and subsequent apoptotic cell death. In addition, a mouse liver regeneration experiment showed a marked decrease in efficiency of hepatic regeneration in CKAP2-depleted liver. These data suggest a physiological role of CKAP2 in the formation of spindle bipolarity, which is necessary for maintaining chromosomal stability.

Cyclin A regulates a cell-cycle-dependent expression of CKAP2 through phosphorylation of Sp1

CKAP2 plays crucial roles in proper chromosome segregation and maintaining genomic stability. CKAP2 protein showed cell-cycle-dependent expression, which reached a maximum level at the G2/M phase and disappeared at the onset of G1 phase. To elucidate the mechanisms underlying cell cycle-dependent expression of CKAP2, we cloned and analyzed the human CKAP2 promoter. The upstream 115-bp region from the transcription start site was sufficient for minimal CKAP2 promoter activity. We identified 2 regulatory sequences; a CHR (-110 to -104 bp) and a GC box (-41 to -32 bp). We confirmed Sp1 bound to the GC box using a supershift assay and a ChIP assay. Mutation in the GC box resulted in a near complete loss of CKAP2 promoter activity while mutation in the CHR decreased the promoter activity by 50%. The CHR mutation showed enhanced activity at the G1/S phase, but still retained cyclic activity. The Chromatin IP revealed that the amount of Sp1 bound to the GC box gradually increased and reached a maximum level at the G2/M phase. The amount of Sp1 bound to the GC box was greatly reduced when Cyclin A was depleted, which was restored by adding Cyclin A/Cdk2 complex back into the nuclear extracts. Together, we concluded that the GC box was responsible for the cyclic activity of human CKAP2 promoter through the phosphorylation of Sp1, possibly by Cyclin A/Cdk complex.

Condensed chromatin staining of CKAP2 as surrogate marker for mitotic figures

PURPOSE

Proliferation activity has long been known to be one of the strongest prognostic factors in many different cancers. Nevertheless, microscopic evaluation of mitotic figures remains time-consuming and, furthermore, is relatively subjective. As the expression of cytoskeleton-associated protein 2 (CKAP2) is closely related to the mitotic phase, CKAP2 was evaluated as a surrogate mitotic figure (MF) marker.

METHODS

A monoclonal antibody specific to human CKAP2 was produced, and immunohistochemistry was performed on normal tissue array sections and 30 breast cancer tissues.

RESULTS

The expression of CKAP2 in the normal human tissues was limited to well-known cell proliferation zones. Strong, readily visible, condensed chromatin staining of CKAP2 was observed specifically in mitotic cells, and the number of these cells was tightly correlated with the MF count in breast cancer tissues (P < 0.001, ρ = 0.743), suggesting its usefulness as a surrogate marker for MF counting.

CONCLUSION

Immunohistochemical staining with CKAP2 monoclonal antibody can be considered to be a new, effective approach to the assessment of proliferation activity in cancer tissues.

Comprehensive proteomic and transcriptomic characterization of hepatic expression signatures affected in p14 liver conditional knockout mice

Scaffold proteins regulate intracellular MAP kinase signaling by providing critical spatial and temporal specificities. We have shown previously that the scaffold protein MEK1 partner (MP1) is localized to late endosomes by the adaptor protein p14. Using conditional gene disruption of p14 in livers of mice (p14(Δhep) ) we analyzed protein and transcript signatures in tissue samples. Further biological network analysis predicted that the differentially expressed transcripts and proteins are involved in cell cycle progression and regulation of cellular proliferation. Although some of the here identified signatures were previously linked to phospho-ERK activity, most of them were novel targets of the late endosomal p14/MP1/MEK/ERK signaling module. Finally, the proliferation defect was confirmed in a chemically induced liver regeneration model in p14(Δhep) knockout mice.

Molecular and functional characterization of allogantigen-specific anergic T cells suitable for cell therapy

BACKGROUND

CD4(+) regulatory T cells are a specialized subset of T cells that actively control immune responses. Several experimental protocols have been used to expand natural regulatory T cells and to generate adaptive type 1 regulatory T cells for regulatory T-cell-based therapies.

DESIGN AND METHODS

The ability of exogenous recombinant human interleukin-10 to induce alloantigen-specific anergy in T cells was investigated and compared to that of interleukin-10 derived from tolerogenic dendritic cells, in mixed lymphocyte cultures. A detailed characterization of the effector functions of the resulting anergized T cells is reported.

RESULTS

Interleukin-10, whether exogenous or derived from tolerogenic dendritic cells, induces a population of alloantigen-specific T cells (interleukin-10-anergized T cells) containing type 1 regulatory T cells, which are anergic and actively suppress alloantigen-specific effector T cells present within the mixed population. Interleukin-10-induced anergy is transforming growth factor-β independent, and is associated with a decreased frequency of alloantigen-specific cytotoxic T lymphocyte precursors, but interleukin-10-anergized T cells are still responsive to third-party, bacterial, and viral antigens. Tolerogenic dendritic cells are more powerful than exogenous interleukin-10 in generating type 1 regulatory T-cell precursors, and are also effective in the context of HLA-matched donors.

CONCLUSIONS

Based on these studies, we have developed an efficient and reproducible in vitro method to generate antigen-specific type 1 regulatory T-cell precursors starting from total peripheral blood cells with minimal cell manipulation and suitable for generating type 1 regulatory T cells for regulatory T-cell-based therapies.

Integrated genomics of susceptibility to alkylator-induced leukemia in mice

Background

Therapy-related acute myeloid leukemia (t-AML) is a secondary, generally incurable, malignancy attributable to chemotherapy exposure. Although there is a genetic component to t-AML susceptibility in mice, the relevant loci and the mechanism(s) by which they contribute to t-AML are largely unknown. An improved understanding of susceptibility factors and the biological processes in which they act may lead to the development of t-AML prevention strategies.

Results

In this work we applied an integrated genomics strategy in inbred strains of mice to find novel factors that might contribute to susceptibility. We found that the pre-exposure transcriptional state of hematopoietic stem/progenitor cells predicts susceptibility status. More than 900 genes were differentially expressed between susceptible and resistant strains and were highly enriched in the apoptotic program, but it remained unclear which genes, if any, contribute directly to t-AML susceptibility. To address this issue, we integrated gene expression data with genetic information, including single nucleotide polymorphisms (SNPs) and DNA copy number variants (CNVs), to identify genetic networks underlying t-AML susceptibility. The 30 t-AML susceptibility networks we found are robust: they were validated in independent, previously published expression data, and different analytical methods converge on them. Further, the networks are enriched in genes involved in cell cycle and DNA repair (pathways not discovered in traditional differential expression analysis), suggesting that these processes contribute to t-AML susceptibility. Within these networks, the putative regulators (e.g., Parp2, Casp9, Polr1b) are the most likely to have a non-redundant role in the pathogenesis of t-AML. While identifying these networks, we found that current CNVR and SNP-based haplotype maps in mice represented distinct sources of genetic variation contributing to expression variation, implying that mapping studies utilizing either source alone will have reduced sensitivity.

Conclusion

The identification and prioritization of genes and networks not previously implicated in t-AML generates novel hypotheses on the biology and treatment of this disease that will be the focus of future research.

Characterization of mitosis-specific phosphorylation of tumor-associated microtubule-associated protein

Tumor-associated microtubule-associated protein (TMAP), also known as cytoskeleton associated protein 2 (CKAP2), has been recently shown to be involved in the assembly and maintenance of mitotic spindle and also plays an essential role in maintaining the fidelity of chromosome segregation during mitosis. We have previously reported that TMAP is phosphorylated at multiple residues specifically during mitosis, and characterized the mechanism and functional importance of phosphorylation at one of the mitosis-specific phosphorylation residues (i.e., Thr-622). However, the phosphorylation events at the remaining mitotic phosphorylation sites of TMAP have not been fully characterized in detail. Here, we report on generation and characterization of phosphorylated Thr-578- and phosphorylated Thr-596-specific antibodies. Using the antibodies, we show that phosphorylation of TMAP at Thr-578 and Thr-596 indeed occurs specifically during mitosis. Immunofluorescent staining using the antibodies shows that these residues become phosphorylated starting at prophase and then become rapidly dephosphorylated soon after initiation of anaphase. Subtle differences in the kinetics of phosphorylation between Thr-578 and Thr-596 imply that they may be under different mechanisms of phosphorylation during mitosis. Unlike the phosphorylation-deficient mutant form for Thr-622, the mutant in which both Thr-578 and Thr-596 had been mutated to alanines did not induce significant delay in progression of mitosis. These results show that the majority of mitosis-specific phosphorylation of TMAP is limited to pre-anaphase stages and suggest that the multiple phosphorylation may not act in concert but serve diverse functions.

Cdk1-cyclin B1-mediated phosphorylation of tumor-associated microtubule-associated protein/cytoskeleton-associated protein 2 in mitosis

During mitosis, establishment of structurally and functionally sound bipolar spindles is necessary for maintaining the fidelity of chromosome segregation. Tumor-associated microtubule-associated protein (TMAP), also known as cytoskeleton-associated protein 2 (CKAP2), is a mitotic spindle-associated protein whose level is frequently up-regulated in various malignancies. Previous reports have suggested that TMAP is a potential regulator of mitotic spindle assembly and dynamics and that it is required for chromosome segregation to occur properly. So far, there have been no reports on how its mitosis-related functions are regulated. Here, we report that TMAP is hyper-phosphorylated at the C terminus specifically during mitosis. At least four different residues (Thr-578, Thr-596, Thr-622, and Ser-627) were responsible for the mitosis-specific phosphorylation of TMAP. Among these, Thr-622 was specifically phosphorylated by Cdk1-cyclin B1 both in vitro and in vivo. Interestingly, compared with the wild type, a phosphorylation-deficient mutant form of TMAP, in which Thr-622 had been replaced with an alanine (T622A), induced a significant increase in the frequency of metaphase cells with abnormal bipolar spindles, which often displayed disorganized, asymmetrical, or narrow and elongated morphologies. Formation of these abnormal bipolar spindles subsequently resulted in misalignment of metaphase chromosomes and ultimately caused a delay in the entry into anaphase. Moreover, such defects resulting from the T622A mutation were associated with a decrease in the rate of protein turnover at spindle microtubules. These findings suggest that Cdk1-cyclin B1-mediated phosphorylation of TMAP is important for and contributes to proper regulation of microtubule dynamics and establishment of functional bipolar spindles during mitosis.

Transient phosphorylation of tumor associated microtubule associated protein (TMAP)/cytoskeleton associated protein 2 (CKAP2) at Thr-596 during early phases of mitosis

Tumor associated microtubule associated protein (TMAP), also known as cytoskeleton associated protein 2 (CKAP2) is a mitotic spindle-associated protein whose expression is cell cycle-regulated and also frequently deregulated in cancer cells. Two monoclonal antibodies (mAbs) against TMAP/CKAP2 were produced: B-1-13 and D-12-3. Interestingly, the reactivity of mAb D-12-3 to TMAP/CKAP2 was markedly decreased specifically in mitotic cell lysate. The epitope mapping study showed that mAb D-12-3 recognizes the amino acid sequence between 569 and 625 and that phosphorylation at T596 completely abolishes the reactivity of the antibody, suggesting that the differential reactivity originates from the phosphorylation status at T596. Immunofluorescence staining showed that mAb D-12-3 fails to detect TMAP/CKAP2 in mitotic cells between prophase and metaphase, but the staining becomes evident again in anaphase, suggesting that phosphorylation at T596 occurs transiently during early phases of mitosis. These results suggest that the cellular functions of TMAP/CKAP2 might be regulated by timely phosphorylation and dephosphorylation during the course of mitosis.

CKAP2 is a spindle-associated protein degraded by APC/C-Cdh1 during mitotic exit

We reported here an efficient and generally applicable genomic analysis that uses transcriptional profiling to identify candidate substrates of regulatory enzymes, such as kinases and ubiquitin ligases. We applied this strategy to the anaphase-promoting complex/cyclosome (APC/C), a ubiquitin ligase that controls sister chromatid separation and exit from mitosis. We found that a microtubule-associated protein, CKAP2, is a substrate of APC/C and demonstrated that ubiquitination and degradation of CKAP2 in vitro require a KEN-box and is mediated by Cdh1, an activator of APC/C. We showed that the levels of CKAP2 fluctuated across the cell cycle in culture cells, high in mitosis and low during mitotic exit. Overexpression of Cdh1 reduced the levels of CKAP2 in a KEN-box-dependent manner, while knockdown of Cdh1 increased the half-life of CKAP2. CKAP2 associated with centrosomal microtubules in late G(2), but only after the separation of the duplicated centrosomes. During mitosis, CKAP2 associated with spindle poles and with spindle microtubules from prophase through anaphase and dis-appeared from microtubules during cytokinesis. The function of CKAP2 during mitosis does not seem essential, as efficient knockdown of CKAP2 neither altered the cell cycle distribution of the cells, nor generated observable mitotic defects. On the other hand, ectopic expression of either the wild-type or a non-degradable CKAP2 led to a mitotic arrest with monopolar spindles containing highly bundled microtubules. We concluded that CKAP2 is a physiological substrate of APC/C during mitotic exit and that a tight regulation of the CKAP2 protein level is critical for the normal mitotic progression.

Functional importance of the anaphase-promoting complex-Cdh1-mediated degradation of TMAP/CKAP2 in regulation of spindle function and cytokinesis

Cytoskeleton-associated protein 2 (CKAP2), also known as tumor-associated microtubule-associated protein (TMAP), is a novel microtubule-associated protein that is frequently upregulated in various malignances. However, its cellular functions remain unknown. A previous study has shown that its protein level begins to increase during G(1)/S and peaks at G(2)/M, after which it decreases abruptly. Ectopic overexpression of TMAP/CKAP2 induced microtubule bundling related to increased microtubule stability. TMAP/CKAP2 overexpression also resulted in cell cycle arrest during mitosis due to a defect in centrosome separation and subsequent formation of a monopolar spindle. We also show that degradation of TMAP/CKAP2 during mitotic exit is mediated by the anaphase-promoting complex bound to Cdh1 and that the KEN box motif near the N terminus is necessary for its destruction. Compared to the wild type, expression of a nondegradable mutant of TMAP/CKAP2 significantly increased the occurrence of spindle defects and cytokinesis failure. These results suggest that TMAP/CKAP2 plays a role in the assembly and maintenance of mitotic spindles, presumably by regulating microtubule dynamics, and its destruction during mitotic exit serves an important role in the completion of cytokinesis and in the maintenance of spindle bipolarity in the next mitosis.

Selective Regression of Cells Expressing Mouse Cytoskeleton-Associated Protein 2 Transcript by Trans-Splicing Ribozyme

Cytoskeleton-associated protein 2 (CKAP2) is known to be highly expressed in primary human cancers as well as most cancer cell lines. CKAP2 functions as microtubule stabilizer and probably as cell proliferation inducer, indicating that CKAP2 might be a potential anticancer target. In this study, we developed a specific ribozyme that can replace mouse CKAP2 (mCKAP2) RNA with new transcripts through trans-splicing reaction. This specific RNA replacement resulted in triggering of transgene activity selectively in mammalian cells that express the mCKAP2 RNA. Simultaneously, the ribozyme reduced the expression level of the target RNA in the cells. Noticeably, the ribozyme selectively induced activity of the suicide gene herpes simplex virus thymidine kinase in cells expressing the mCKAP2 RNA and thereby specifically retarded the survival of these cells with ganciclovir treatment. This mCKAP2-specific ribozyme will be useful for validation of the RNA replacement as cancer gene therapy approach in mouse model with syngeneic tumors.