Aurora A is differentially expressed and regulated in chromosomal and microsatellite instable sporadic colorectal cancers

Aurora Kinase A Is a Prognostic Marker in Colorectal Adenocarcinoma

BACKGROUND

Aurora kinase A (AURKA), or STK15/BTAK, is a member of the serine/threonine kinase family and plays important roles in mitosis and chromosome stability. This study investigated the clinical significance of AURKA expression in colorectal cancer patients in Korea.

METHODS

AURKA protein expression was evaluated by immunohistochemistry in 151 patients with colorectal adenocarcinoma using tissue microarray blocks. We analyzed the relationship between clinicopathological characteristics and AURKA expression. In addition, the prognostic significance of various clinicopathological data for progression-free survival (PFS) was assessed. Also we evaluated copy number variations by array comparative genomic hybridization and AURKA gene amplification using fluorescence in situ hybridization in colorectal carcinoma tissues.

RESULTS

AURKA gene amplification was found more frequently in the 20q13.2-13.33 gain-positive group than the group with no significant gain on the AURKA-containing locus. AURKA protein expression was detected in 45% of the cases (68/151). Positive staining for AURKA was observed more often in male patients (p = .035) and distally located tumors (p = .021). PFS was shorter in patients with AURKA expression compared to those with low-level AURKA expression (p < .001). Univariate analysis revealed that AURKA expression (p = .001), age (p = .034), lymphatic invasion (p = .001), perineural invasion (p = .002), and TNM stage (p = .013) significantly affected PFS. In a multivariate analysis of PFS, a Cox proportional hazard model confirmed that AURKA expression was an independent and significant prognostic factor in colorectal adenocarcinoma (hazard ratio, 3.944; p < .001).

CONCLUSIONS

AURKA could serve as an independent factor to predict a poor prognosis in Korean colorectal adenocarcinoma patients.

Fibroblast activation protein-α, a stromal cell surface protease, shapes key features of cancer associated fibroblasts through proteome and degradome alterations

Cancer associated fibroblasts (CAFs) constitute an abundant stromal component of most solid tumors. Fibroblast activation protein (FAP) α is a cell surface protease that is expressed by CAFs. We corroborate this expression profile by immunohistochemical analysis of colorectal cancer specimens. To better understand the tumor-contextual role of FAPα, we investigate how FAPα shapes functional and proteomic features of CAFs using loss- and gain-of function cellular model systems. FAPα activity has a strong impact on the secreted CAF proteome ("secretome"), including reduced levels of anti-angiogenic factors, elevated levels of transforming growth factor (TGF) β, and an impact on matrix processing enzymes. Functionally, FAPα mildly induces sprout formation by human umbilical vein endothelial cells. Moreover, loss of FAPα leads to a more epithelial cellular phenotype and this effect was rescued by exogenous application of TGFβ. In collagen contraction assays, FAPα induced a more contractile cellular phenotype. To characterize the proteolytic profile of FAPα, we investigated its specificity with proteome-derived peptide libraries and corroborated its preference for cleavage carboxy-terminal to proline residues. By "terminal amine labeling of substrates" (TAILS) we explored FAPα-dependent cleavage events. Although FAPα acts predominantly as an amino-dipeptidase, putative FAPα cleavage sites in collagens are present throughout the entire protein length. In contrast, putative FAPα cleavage sites in non-collagenous proteins cluster at the amino-terminus. The degradomic study highlights cell-contextual proteolysis by FAPα with distinct positional profiles. Generally, our findings link FAPα to key aspects of CAF biology and attribute an important role in tumor-stroma interaction to FAPα.

Aurora B expression and histone variant H1.4S27 phosphorylation are no longer coordinated during metaphase in aneuploid colorectal carcinomas

Experimental model systems identified phosphorylation of linker histone variant H1.4 at Ser 27 (H1.4S27p) as a novel mitotic mark set by Aurora B kinase. Here, we examined expression of Aurora B and H1.4S27p in colorectal carcinoma (CRC) cell lines (HCT116, DLD1, Caco-2, HT29) and tissue specimens (n = 36), in relation to microsatellite instability (MSI) status and ploidy. In vitro, Aurora B (pro-/meta-/anaphase) and H1.4S27p (pro-/metaphase) were localized in mitotic figures. The proportion of labeled mitoses was significantly different between cell lines for Aurora B (p = 0.019) but not for H1.4S27p (p = 0.879). For Aurora B, these differences were not associated with an altered Aurora B gene copy number (FISH) or messenger RNA (mRNA) expression level (qRT-PCR). Moreover, Aurora B expression and H1.4S27 phosphorylation were no longer coordinated during metaphase in aneuploid HT29 cells (p = 0.039). In CRCs, immunoreactivity for Aurora B or H1.4S27p did not correlate with T- or N-stage, grade, or MSI status. However, metaphase labeling of H1.4S27p was significantly higher in diploid than in aneuploid CRCs (p = 0.011). Aurora B was significantly correlated with H1.4S27p-positive metaphases in MSI (p = 0.010) or diploid (p = 0.003) CRCs. Finally, combined classification of MSI status and ploidy revealed a significant positive correlation of Aurora B with H1.4S27p in metaphases of diploid/MSI (p = 0.010) and diploid/microsatellite-stable (MSS; p = 0.031) but not of aneuploid/MSS (p = 0.458) CRCs. The present study underlines the functional link of Aurora B expression and H1.4S27p during specific phases of mitosis in diploid and/or MSI-positive CRCs in vitro and in situ. Importantly, the study shows that the coordination between Aurora B expression and phosphorylation of H1.4 at Ser 27 is lost in cycling aneuploid CRC cells.

Proteins related to the spindle and checkpoint mitotic emphasize the different pathogenesis of hypoplastic MDS

Some studies show that alterations in expression of proteins related to mitotic spindle (AURORAS KINASE A and B) and mitotic checkpoint (CDC20 and MAD2L1) are involved in chromosomal instability and tumor progression in various solid and hematologic malignancies. This study aimed to evaluate these genes in MDS patients. The cytogenetics analysis was carried out by G-banding, AURKA and AURKB amplification was performed using FISH, and AURKA, AURKB, CDC20 and MAD2L1 gene expression was performed by qRT-PCR in 61 samples of bone marrow from MDS patients. AURKA gene amplification was observed in 10% of the cases, which also showed higher expression levels than the control group (p=0.038). Patients with normo/hypercellular BM presented significantly higher expression levels than hypocellular BM patients, but normo and hypercellular BM groups did not differ. After logistic regression analysis, our results showed that HIGH expression levels were associated with increased risk of developing normo/hypercellular MDS. It also indicated that age is associated with AURKA, CDC20 and MAD2L1 HIGH expression levels. The distinct expression of hypocellular patients emphasizes the prognostic importance of cellularity to MDS. The amplification/high expression of AURKA suggests that the increased expression of this gene may be related to the pathogenesis of disease.

STAT3 expression, activity and functional consequences of STAT3 inhibition in esophageal squamous cell carcinomas and Barrett's adenocarcinomas

Signal transducer and activator of transcription 3 (STAT3) is altered in several epithelial cancers and represents a potential therapeutic target. Here, STAT3 expression, activity and cellular functions were examined in two main histotypes of esophageal carcinomas. In situ, immunohistochemistry for STAT3 and STAT3-Tyr705 phosphorylation (P-STAT3) in esophageal squamous cell carcinomas (ESCC, n=49) and Barrett's adenocarcinomas (BAC, n=61) revealed similar STAT3 expression in ESCCs and BACs (P=0.109), but preferentially activated P-STAT3 in ESCCs (P=0.013). In vitro, strong STAT3 activation was seen by epidermal growth factor (EGF) stimulation in OE21 (ESCC) cells, whereas OE33 (BAC) cells showed constitutive weak STAT3 activation. STAT3 knockdown significantly reduced cell proliferation of OE21 (P=0.0148) and OE33 (P=0.0243) cells. Importantly, STAT3 knockdown reduced cell migration of OE33 cells by 2.5-fold in two types of migration assays (P=0.073, P=0.015), but not in OE21 cells (P=0.1079, P=0.386). Investigation of transcriptome analysis of STAT3 knockdown revealed a reduced STAT3 level associated with significant downregulation of cell cycle genes in both OE21 (P<0.0001) and OE33 (P=0.01) cells. In contrast, genes promoting cell migration (CTHRC1) were markedly upregulated in OE21 cells, whereas a gene linked to tight-junction stabilization and restricted cell motility (SHROOM2) was downregulated in OE21 but upregulated in OE33 cells. This study shows frequent, but distinct, patterns of STAT3 expression and activation in ESCCs and BACs. STAT3 knockdown reduces cell proliferation in ESCC and BAC cells, inhibits migration of BAC cells and may support cell migration of ESCC cells. Thereby, novel STAT3-regulated genes involved in ESCC and BAC cell proliferation and cell migration were identified. Thus, STAT3 may be further exploited as a potential novel therapeutic target, however, by careful distinction between the two histotypes of esophageal cancers.

Occurrence of Aurora A positive multipolar mitoses in distinct molecular classes of colorectal carcinomas and effect of Aurora A inhibition

Aurora A "over-"expression may induce supernumerary centrosomes, respective multipolar mitoses, and aneuploidy. Here, we examined Aurora A positive multipolar mitoses in aneuploid, microsatellite-stable (MSS, "CIN-type") versus near-diploid, microsatellite-instable (MSI, "MIN-type") colorectal carcinomas (CRC) and CRC cell lines as well as the effect of Aurora A inhibition in CRC cell lines. In situ, three-dimensional immunofluorescence (3D-IF) revealed Aurora A positive multipolar mitoses in both CIN- (n = 8) and MIN- (n = 10) type primary CRCs with similar frequencies (CIN: 27 ± 14%; MIN: 34 ± 14%, P = 0.224). In vitro, Aurora A positive multipolar mitoses were detected in asynchronized or thymidine synchronized CIN-type (HT29, CaCo-2), but not MIN-type (HCT116, DLD-1) CRC cells. Nocodazole treatment arrested mitotic cells with multiple centrosomal Aurora A signals in CIN- and MIN-type CRC cells, albeit to a lower extent in CaCo-2 cells. This was associated with concomitant activation of Aurora A (T288 phosphorylation) and Polo-like kinase 1 (PLK-1, T210 phosphorylation). Aurora A inhibition by siRNA resulted in increased apoptosis (>50%) in all cell lines, but did not abolish PLK-1 expression. Double 3D-IF revealed that Aurora A siRNA treated, still viable CIN-type (HT29, CaCo-2) CRC cells were Aurora A negative and mostly in prophase/(pro)metaphase with maintained phosphorylated PLK-1 T210 expression. Aurora A positive multipolar mitoses occur in both aneuploid, CIN- and near-diploid MIN-type CRCs. This appears to be largely independent of Aurora A expression alone. Although Aurora A inhibition causes apoptosis in both CIN- and MIN-type CRC cells, remaining PLK-1 activation by other factors may affect therapeutic Aurora inhibition.

Occurrence of multipolar mitoses and association with Aurora-A/-B kinases and p53 mutations in aneuploid esophageal carcinoma cells

Background

Aurora kinases and loss of p53 function are implicated in the carcinogenesis of aneuploid esophageal cancers. Their association with occurrence of multipolar mitoses in the two main histotypes of aneuploid esophageal squamous cell carcinoma (ESCC) and Barrett's adenocarcinoma (BAC) remains unclear. Here, we investigated the occurrence of multipolar mitoses, Aurora-A/-B gene copy numbers and expression/activation as well as p53 alterations in aneuploid ESCC and BAC cancer cell lines.

Results

A control esophageal epithelial cell line (EPC-hTERT) had normal Aurora-A and -B gene copy numbers and expression, was p53 wild type and displayed bipolar mitoses. In contrast, both ESCC (OE21, Kyse-410) and BAC (OE33, OE19) cell lines were aneuploid and displayed elevated gene copy numbers of Aurora-A (chromosome 20 polysomy: OE21, OE33, OE19; gene amplification: Kyse-410) and Aurora-B (chromosome 17 polysomy: OE21, Kyse-410). Aurora-B gene copy numbers were not elevated in OE19 and OE33 cells despite chromosome 17 polysomy. Aurora-A expression and activity (Aurora-A/phosphoT288) was not directly linked to gene copy numbers and was highest in Kyse-410 and OE33 cells. Aurora-B expression and activity (Aurora-B/phosphoT232) was higher in OE21 and Kyse-410 than in OE33 and OE19 cells. The mitotic index was highest in OE21, followed by OE33 > OE19 > Kyse-410 and EPC-hTERT cells. Multipolar mitoses occurred with high frequency in OE33 (13.8 ± 4.2%), followed by OE21 (7.7 ± 5.0%) and Kyse-410 (6.3 ± 2.0%) cells. Single multipolar mitoses occurred in OE19 (1.0 ± 1.0%) cells. Distinct p53 mutations and p53 protein expression patterns were found in all esophageal cancer cell lines, but complete functional p53 inactivation occurred in OE21 and OE33 only.

Conclusions

High Aurora-A expression alone is not associated with overt multipolar mitoses in aneuploid ESCC and BAC cancer cells, as specifically shown here for OE21 and OE33 cells, respectively. Additional p53 loss of function mutations are necessary for this to occur, at least for invasive esophageal cancer cells. Further assessment of Aurora kinases and p53 interactions in cells or tissue specimens derived from non-invasive dysplasia (ESCC) or intestinal metaplasia (BAC) are necessary to disclose a potential causative role of Aurora kinases and p53 for development of aneuploid, invasive esophageal cancers.

Copy number increase of aurora kinase A in colorectal cancers: a correlation with tumor progression

The centrosome-associated kinase aurora A (AURKA) is involved in genetic instability and is over-expressed in several human carcinomas including colorectal cancer (CRC). The choromosome locus of AURKA, 20q13, is frequently amplified in CRC, and the functional impact of such regions needs to be extensively investigated in large amount of clinical samples. Case-matched tissues of colorectal adenocarcinomas and adjacent normal epithelium (n= 134) were included in this study. Quantitative PCR was carried out to examine the copy number and mRNA level of AURKA in CRC. Our results showed that copy number gains of AUKRA were detected in a relative high percentage of CRC samples (32.4%, 43 of 134). There was a positive correlation between copy number increase of AURKA and tumor progression. And copy number gains of AURKA also showed a positive correlation with mRNA over-expression in CRC. However, the expression level of AURKA mRNA was also enhanced in the group of CRC samples with unaltered copy numbers. These findings indicated that sporadic colorectal cancers exhibit different mechanisms of aurora A regulation and this may impact the efficacy of aurora-targeted therapies.

Harmonic filters for 3D multichannel data: rotation invariant detection of mitoses in colorectal cancer

In this paper, we present a novel approach for a trainable rotation invariant detection of complex structures in 3D microscopic multichannel data using a nonlinear filter approach. The basic idea of our approach is to compute local features in a window around each 3D position and map these features by means of a nonlinear mapping onto new local harmonic descriptors of the local window. These local harmonic descriptors are then combined in a linear way to form the output of the filter. The optimal combination of the computed local harmonic descriptors is determined in previous training step, and allows the filter to be adapted to an arbitrary structure depending on the problem at hand. Our approach is not limited to scalar-valued images and can also be used for vector-valued (multichannel) images such as gradient vector flow fields. We present realizations of a scalar-valued and a vector-valued multichannel filter. Our proposed algorithm was quantitatively evaluated on colorectal cancer cell lines (cells grown under controlled conditions), on which we successfully detected complex 3D mitotic structures. For a qualitative evaluation we tested our algorithms on human 3D tissue samples of colorectal cancer. We compare our results with a steerable filter approach as well as a morphology-based approach.

Copy-number increase of AURKA in gastric cancers in a Chinese population: a correlation with tumor progression

The centrosome-associated kinase aurora A (AURKA) has been shown to be involved in genetic instability and to be over-expressed in several human carcinomas including gastric cancers (GCs). The chromosome locus of AURKA, 20q13, is frequently amplified in GCs, and the functional impact of such regions needs to be extensively investigated in large amount of clinical samples. Case-matched tissues of gastric carcinomas and adjacent normal epithelium (n=141) were included in this study. Quantitative PCR was carried out to examine the copy number and mRNA expression of AURKA in GCs. Our results showed copy-number gains of AUKRA were detected in a relative high percentage of GC samples (30.5%, 43 out of 141). There was a positive correlation between copy-number increase of AURKA and tumor progression. And copy-number gains of AURKA also showed a positive correlation with mRNA over-expression in GCs. However, expression level of AURKA mRNA was also enhanced in the group of GC samples with unaltered copy numbers. These findings indicated that sporadic gastric cancers exhibit different mechanisms of AURKA regulation and that this may impact the efficacy of aurora-targeted therapies.

Aurora-a is essential for the tumorigenic capacity and chemoresistance of colorectal cancer stem cells

Colorectal cancer stem cells (CR-CSC) are responsible for the generation and maintenance of intestinal tumors and are highly resistant to conventional chemotherapeutic agents. Aurora-A, a serine-threonine kinase involved in mitosis regulation, plays multiple key functions in tumor initiation and progression. We found that Aurora-A is overexpressed in primary colorectal tumor cells, in the CR-CSC fraction, and in stem cell-derived differentiated cells, compared with normal colon tissue. Aurora-A expression was functionally linked to centrosome amplification in CR-CSC, as indicated by the decrease in cells with multiple centrosomes that followed Aurora-A silencing. Knockdown of Aurora-A resulted in growth inhibition of CR-CSC, alteration of cell cycle kinetics, and downregulation of the expression levels of antiapoptotic Bcl-2 family members, strongly sensitizing to chemotherapy-induced cell death. Moreover, Aurora-A silencing compromised the ability to form tumor xenografts in immunocompromised mice and reduced the migratory capacity of CR-CSC. Altogether, these results indicate that Aurora-A is essential for CR-CSC regeneration and resistance to cytotoxic stimuli and suggest that therapies directed against Aurora-A may effectively target the stem cell population in colorectal cancer.

Elevated endogenous expression of the dominant negative basic helix-loop-helix protein ID1 correlates with significant centrosome abnormalities in human tumor cells

Background

ID proteins are dominant negative inhibitors of basic helix-loop-helix transcription factors that have multiple functions during development and cellular differentiation. Ectopic (over-)expression of ID1 extends the lifespan of primary human epithelial cells. High expression levels of ID1 have been detected in multiple human malignancies, and in some have been correlated with unfavorable clinical prognosis. ID1 protein is localized at the centrosomes and forced (over-)expression of ID1 results in errors during centrosome duplication.

Results

Here we analyzed the steady state expression levels of the four ID-proteins in 18 tumor cell lines and assessed the number of centrosome abnormalities. While expression of ID1, ID2, and ID3 was detected, we failed to detect protein expression of ID4. Expression of ID1 correlated with increased supernumerary centrosomes in most cell lines analyzed.

Conclusions

This is the first report that shows that not only ectopic expression in tissue culture but endogenous levels of ID1 modulate centrosome numbers. Thus, our findings support the hypothesis that ID1 interferes with centrosome homeostasis, most likely contributing to genomic instability and associated tumor aggressiveness.