Significance of SHP-1 and SHP-2 expression in human papillomavirus infected Condyloma acuminatum and cervical cancer

Synergistic Cytotoxicity Effect of 5-fluorouracil and SHP2 Inhibitor Demethylincisterol A3 on Cervical Cancer Cell

BACKGROUND

Demethylincisterol A3 (DTA3) has been identified as an SHP2 inhibitor and suppresses the growth of many cancer cells. 5-Fluorouracil (5-FU) is widely used for the clinical treatment of various cancers. However, the combined effects of 5-FU and DTA3 on cervical cancer cells remain unknown.

OBJECTIVE

This study evaluates the mechanism of the combined effects of 5-FU and DTA3 in cervical cancer cells.

METHODS

The synergistic cytotoxic effects of 5-FU and DTA3 in cervical cancer cells were calculated. Apoptosis was analysed by flow cytometry. Western blot analyses were used to examine the related signalling pathways.

RESULTS

DTA3 and 5-FU synergized to induce apoptosis and repress proliferation of cervical cancer cells by downregulating the activation of PI3K/AKT and NF-κB signalling pathway. We provided evidence that the upregulation of SHP2 expression by transfection significantly inhibited the cytotoxicity of 5-FU and DTA3. SHP2 knockdown enhanced the antiproliferation activity of 5-FU, indicating targeting SHP2 sensitized cervical cancer cells to 5-FU.

CONCLUSION

Our study demonstrates that SHP2 inhibitor DTA3 and 5-FU have a synergistic cytotoxic effect on cervical cancer cells. The synergistic combination of SHP2 inhibitor and 5-FU may present a promising strategy for the treatment of cervical cancer.

Effects of Sambucus Ebulus Extract on Cell Proliferation and Viability of Triple-Negative Breast Cancer: An In Vitro and In Vivo Study

BACKGROUND

Triple-negative breast cancer (TNBC) accounts for 15% of all breast cancer (BC) cases and is a severe type of BC. Since medicinal herbs containing biocompatible substances that are accepted by patient more than chemical therapeutics, they can be considered a safe option for treating BC.

OBJECTIVE

This study evaluated the effect of Sambucus Ebulus (S. ebulus) extract on a model of TNBC.

METHODS

S. ebulus extract was prepared using petroleum ether, ethyl acetate, and methanol. The petroleum ether extract was fractionated and analyzed using vacuum liquid chromatography and GC-MS, respectively. MDA-MB-231 and MCF-10A were used as TNBC and normal breast cells, respectively. Flowcytometry and MTT assays were performed to evaluate cell cycle, apoptosis, and viability of the cells. Gene expression analysis was performed using RT-qPCR. Nude mouse allograft tumor models were used, and pathological sections were evaluated.

RESULTS

The findings indicated that S. ebulus extract remarkably decreased cell proliferation and viability. The extract had no toxicity to the normal breast cells but efficiently killed the cancer cells. Cell cycle- and apoptosis-related gene expression showed that fraction 4 of S. ebulus extract significantly increased the expression of Bax, Bak, P53, and c-MYC.

CONCLUSION

This study showed satisfactory results of the effect of S. ebulus extract on clearing BC cells both in vitro and in vivo. Thus, S. ebulus extract may be a safe herbal compound for eliminating BC cells without toxicity to host cells.

Immunogenomic Identification for Predicting the Prognosis of Cervical Cancer Patients

Cervical cancer is primarily caused by the infection of high-risk human papillomavirus (hrHPV). Moreover, tumor immune microenvironment plays a significant role in the tumorigenesis of cervical cancer. Therefore, it is necessary to comprehensively identify predictive biomarkers from immunogenomics associated with cervical cancer prognosis. The Cancer Genome Atlas (TCGA) public database has stored abundant sequencing or microarray data, and clinical data, offering a feasible and reliable approach for this study. In the present study, gene profile and clinical data were downloaded from TCGA, and the Immunology Database and Analysis Portal (ImmPort) database. Wilcoxon-test was used to compare the difference in gene expression. Univariate analysis was adopted to identify immune-related genes (IRGs) and transcription factors (TFs) correlated with survival. A prognostic prediction model was established by multivariate cox analysis. The regulatory network was constructed and visualized by correlation analysis and Cytoscape, respectively. Gene functional enrichment analysis was performed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). A total of 204 differentially expressed IRGs were identified, and 22 of them were significantly associated with the survival of cervical cancer. These 22 IRGs were actively involved in the JAK-STAT pathway. A prognostic model based on 10 IRGs (APOD, TFRC, GRN, CSK, HDAC1, NFATC4, BMP6, IL17RD, IL3RA, and LEPR) performed moderately and steadily in squamous cell carcinoma (SCC) patients with FIGO stage I, regardless of the age and grade. Taken together, a risk score model consisting of 10 novel genes capable of predicting survival in SCC patients was identified. Moreover, the regulatory network of IRGs associated with survival (SIRGs) and their TFs provided potential molecular targets.

Shp2 expression is upregulated in cervical cancer, and Shp2 contributes to cell growth and migration and reduces sensitivity to cisplatin in cervical cancer cells

Src homology phosphotyrosine phosphatase 2 (Shp2) has been found to be overexpressed in cervical cancer tissues. However, the influence of Shp2 on the biological behavior and sensitivity to cisplatin of cervical cancer cells remains unclear. We aimed to assess Shp2 expression in cervical tissues and cell lines and to detect the influence of Shp2 knockdown and overexpression on the biological behavior and sensitivity to cisplatin in cervical cancer cells. We found that Shp2 expression was significantly upregulated in cervical cancer tissues and cell lines, and Shp2 overexpression was associated with lymph node metastasis and a high human papillomavirus (HPV) DNA load. Shp2 knockdown inhibited cell growth and migration and enhanced sensitivity to cisplatin in the HeLa and SiHa cervical cancer cell lines. In contrast, Shp2 overexpression had the opposite effects. These tumor-promoting effects of Shp2 may be partly related to Akt signaling. In conclusion, Shp2 is involved in the occurrence and development of cervical cancer and may confer cisplatin resistance in cervical cancer. Shp2 blockade may be a new strategy for cervical cancer treatment.

The presence of Y674/Y675 phosphorylated NTRK1 via TP53 repression of PTPN6 expression as a potential prognostic marker in neuroblastoma

The tumor suppressor TP53 promotes nerve growth factor receptor (NTRK1) -Y674/Y675 phosphorylation (NTRK1-pY674/pY675) via repression of the NTRK1 phosphatase PTPN6 in a ligand-independent manner, resulting in suppression of breast cancer cell proliferation. Moreover, NTRK1-pY674/pY675 together with low levels of PTPN6 and TP53 expression is associated with favorable disease-free survival of breast cancer patients. We determined whether in neuroblastoma this protein expression pattern impacts relapse-free survival (RFS). NTRK1-pY674/pY675, PTPN6, and TP53 expression was assessed in 98 neuroblastoma samples by immunohistochemistry. Association between expression levels and RFS was investigated by multivariate and Kaplan-Meier analysis. Mutant or wild-type TP53 was identified by sequencing tumor DNA. Tumors expressing NTRK1-pY674/pY675 and low or undetectable levels of PTPN6 and TP53 were significantly associated with 5-year RFS (P = .014) when the dataset was stratified by MYCN amplification, segmental chromosomal abnormalities and histology. Similar results were observed with tumors expressing wild-type TP53, NTRK1-pY674/pY675 and low or undetectable levels of PTPN6. Kaplan-Meier analysis demonstrated a significant correlation (P = .004), with a 50% probability of RFS (median survival 4.73 years) when present compared with 19.51% (median survival 11.63 months) when absent. Similar results were seen with non-amplified MYCN or unfavorable/undifferentiating samples and tumors from patients aged 18 months or less. Importantly, NTRK1-pY674/pY675 is an independent predictor of improved RFS. These results strongly suggest that NTRK1-pY674/pY675 together with wild-type TP53 and undetectable or low levels of PTPN6 expression is a potential biomarker of improved RFS of neuroblastoma patients. The predictive value of NTRK1-pY674/pY675 together with wild-type TP53 and low PTPN6 expression could contribute to neuroblastoma patient prognosis.

SHP-2在结直肠癌组织中的表达及临床意义

目的

探讨SHP-2蛋白在结直肠癌中的表达情况及其与病理特征的关系.

方法

采用免疫组织化学法和Western blot方法检测SHP-2蛋白在人结直肠癌组织中的表达情况, 分析其与患者临床病理因素的关系.

结果

结直肠癌组织中SHP-2阳性表达率为25.6%(43/168), 与正常结直肠组织比较, 差异有统计学意义(P<0.05). 结直肠癌组织中SHP-2的蛋白水平为0.2396±0.0655, 与配对正常结直肠组织比较(0.7665±0.1133), 差异有统计学意义(P<0.0001). SHP-2蛋白的低表达与分化程度和淋巴结转移有关, 与性别、年龄、浸润程度、远处转移、TNM分期无关.

结论

SHP-2可能在结直肠癌的发生发展过程中起抑制作用, 并可能成为潜在的治疗靶点.

Alteration of SHP-1/p-STAT3 Signaling: A Potential Target for Anticancer Therapy

The Src homology 2 (SH2) domain-containing protein tyrosine phosphatase 1 (SHP-1), a non-receptor protein tyrosine phosphatase, has been reported as a negative regulator of phosphorylated signal transducer and activator of transcription 3 (STAT3) and linked to tumor development. In this present review, we will discuss the importance and function of SHP-1/p-STAT3 signaling in nonmalignant conditions as well as malignancies, its cross-talk with other pathways, the current clinical development and the potential role of inhibitors of this pathway in anticancer therapy and clinical relevance of SHP-1/p-STAT3 in cancers. Lastly, we will summarize and highlight work involving novel drugs/compounds targeting SHP-1/p-STAT3 signaling and combined strategies that were/are discovered in our and our colleagues’ laboratories.

Clinical significance of leukocyte-associated immunoglobulin-like receptor-1 expression in human cervical cancer

Leukocyte-associated immunoglobulin-like receptor-1 (LAIR-1) is broadly expressed on the majority of immune cells; however, the biological role of LAIR in solid tumors has yet to be elucidated. In the present study, using immunohistochemical staining analysis, the expression of LAIR-1 in human cervical cancer (HCC) and nontumor-adjacent tissue specimens was determined, and the results indicated that the expression of LAIR-1 in HCC tissue was higher compared with that in noncancerous tissue. The χ² test was used to analyze the correlation between the expression of LAIR-1 in tumor tissues with clinicopathological parameters. The results showed that the expression of LAIR-1 in the cancer cell nucleus was significantly associated with tumor size, pathological differentiation, T classification and clinical stage. In addition, the expression in the cytoplasm was evidently associated with the number of positive lymph nodes. The HCC cell line, ME-180, which does not express LAIR-1, was stably transfected using LAIR-1 cDNA. Cell Counting Kit-8 and an annexin V assay showed that the overexpression of LAIR-1 in ME-180 cells suppressed the proliferation and anti-apoptosis capacity of the cells. These findings demonstrated that LAIR-1 is markedly overexpressed in HCC tissue, and that its expression status is associated with tumor progression. LAIR-1 may be a biomarker and target in the diagnosis and treatment of patients with HCC.

Protein tyrosine phosphatase SHP-1 sensitizes EGFR/HER-2 positive breast cancer cells to trastuzumab through modulating phosphorylation of EGFR and HER-2

Background

Trastuzumab resistance in HER-2 positive breast cancer cells is closely related to overexpression of both epidermal growth factor receptor (EGFR) and human epidermal receptor (HER-2). SHP-1 has been demonstrated to downregulate tyrosine kinase activity including EGFR via its phosphatase function, but its effect on HER-2 activity is still unknown. Here, we examined the hypothesis that SHP-1 enhances the anticancer efficacy of trastuzumab in EGFR/HER-2 positive breast cancer cells through combining dual inhibition of EGFR and HER-2.

Methods

Trastuzumab-resistant breast cancer SKBr-3 cells were generated by long-term in vitro culture of SKBr-3cells in the presence of trastuzumab. The SHP-1 was ectopically expressed by stable transfection. The activity and expression of EGFR, HER-2, and downstream signaling pathways were tested by Western blot. Cell viability was examined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and apoptosis was examined by flow cytometry. The binding between SHP-1 and EGFR/HER-2 was evaluated by immunoprecipitation assay and bimolecular fluorescence complementation. The effects of SHP-1 on tumorigenicity and trastuzumab sensitivity were confirmed via in vivo xenograft model.

Results

Trastuzumab-resistant SKBr-3 cells showed aberrant co-expression of EGFR and HER-2. Introduction of wild-type SHP-1 inhibited cell proliferation, clone formation, and promoted the apoptosis induced by trastuzumab. Meanwhile, SHP-1 overexpression reduced phosphorylation levels of EGFR and HER-2 both in parental and trastuzumab-resistant SKBr-3 cells. In vivo study showed an increased antitumor effect of trastuzumab in SHP-1 overexpressed xenografts. At last, we discovered that SHP-1 can make complexes with both EGFR and HER-2, and both phospho-EGFR and phosphor-HER-2 levels in wild-type SHP-1 immunoprecipitates were less than those in phosphatase-inactive SHP-1 (C453S) immunoprecipitates, indicating that EGFR and HER-2 are potential substrates of SHP-1.

Conclusion

Taken together, we have demonstrated that the SHP-1 is a negative regulatory factor of the tyrosine kinase activity of HER-2 and EGFR through inhibiting phosphorylation. Dual targeting of EGFR and HER-2, by combining trastuzumab with SHP-1 overexpression, may improve response in HER-2 overexpressing breast cancer cells that also express high levels of EGFR.

Gamma tocotrienol targets tyrosine phosphatase SHP2 in mammospheres resulting in cell death through RAS/ERK pathway

Background

There is increasing evidence supporting the concept of cancer stem cells (CSCs), which are responsible for the initiation, growth and metastasis of tumors. CSCs are thus considered the target for future cancer therapies. To achieve this goal, identifying potential therapeutic targets for CSCs is essential.

Methods

We used a natural product of vitamin E, gamma tocotrienol (gamma-T3), to treat mammospheres and spheres from colon and cervical cancers. Western blotting and real-time RT-PCR were employed to identify the gene and protein targets of gamma-T3 in mammospheres.

Results

We found that mammosphere growth was inhibited in a dose dependent manner, with total inhibition at high doses. Gamma-T3 also inhibited sphere growth in two other human epithelial cancers, colon and cervix. Our results suggested that both Src homology 2 domain-containing phosphatase 1 (SHP1) and 2 (SHP2) were affected by gamma-T3 which was accompanied by a decrease in K- and H-Ras gene expression and phosphorylated ERK protein levels in a dose dependent way. In contrast, expression of self-renewal genes TGF-beta and LIF, as well as ESR signal pathways were not affected by the treatment. These results suggest that gamma-T3 specifically targets SHP2 and the RAS/ERK signaling pathway.

Conclusions

SHP1 and SHP2 are potential therapeutic targets for breast CSCs and gamma-T3 is a promising natural drug for future breast cancer therapy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1614-1) contains supplementary material, which is available to authorized users.

Immune biomarkers of anti-EGFR monoclonal antibody therapy

The tumor antigen (TA)-targeted monoclonal antibodies (mAb) cetuximab and panitumumab target the human epidermal growth factor receptor and have been integrated into treatment regimens for advanced squamous cell carcinoma of the head and neck (SCCHN). The therapeutic efficacy of these mAbs has been found to be enhanced when combined with radiotherapy and chemotherapy. However, clinical trials indicate that these findings are limited to fewer than 20% of treated patients. Therefore, identifying patients who are likely to benefit from these agents is crucial to improving therapeutic strategies. Interestingly, it has been noted that TA-targeted mAbs mediate their effects by contributing to cell-mediated cytotoxicity in addition to inhibition of downstream signaling pathways. Here, we describe the potential immunogenic mechanisms underlying these clinical findings, their role in the varied clinical response and identify the putative biomarkers of antitumor activity. We review potential immunological biomarkers that affect mAb therapy in SCCHN patients, the implications of these findings and how they translate to the clinical scenario, which are critical to improving patient selection and ultimately outcomes for patients undergoing therapy.

Upregulation of Src homology phosphotyrosyl phosphatase 2 (Shp2) expression in oral cancer and knockdown of Shp2 expression inhibit tumor cell viability and invasion in vitro

OBJECTIVE

This study investigated the clinical significance of Shp2 protein expression in oral squamous cell carcinoma (OSCC) and elucidated its biologic significance in OSCC cells.

STUDY DESIGN

A total of 88 OSCC cases were used to assess Shp2 expression, out of which 70 were for immunohistochemistry and 18 paired tumors vs normal tissues were for Western blot of Shp2 expression. OSCC cells were used to assess the effects of Shp2 knockdown for cell viability, apoptosis, invasion, and protein expressions.

RESULTS

Expression of Shp2 protein was significantly upregulated in OSCC tissues compared with the normal tissues, and Shp2 overexpression was associated with advanced tumor clinical stages and lymph node metastasis ex vivo. Knockdown of Shp2 expression in vitro inhibited OSCC cell viability and invasion but induced apoptosis by regulating expression of the apoptosis-related proteins.

CONCLUSIONS

The data indicated that Shp2 may play an important role in OSCC progression. Further studies will investigate whether a target of Shp2 expression could be a novel therapeutic strategy for clinical control of OSCC.

SHP2 is overexpressed and inhibits pSTAT1-mediated APM component expression, T-cell attracting chemokine secretion, and CTL recognition in head and neck cancer cells

PURPOSE

Human leukocyte antigen (HLA) class I antigen processing machinery (APM) component downregulation permits escape of malignant cells from recognition by cytotoxic T lymphocytes (CTL) and correlates with poor prognosis in patients with head and neck cancer (HNC). Activated STAT1 (pSTAT1) is necessary for APM component expression in HNC cells. We investigated whether an overexpressed phosphatase was responsible for basal suppression of pSTAT1 and subsequent APM component-mediated immune escape in HNC cells.

EXPERIMENTAL DESIGN

Immunohistochemical staining and reverse transcription PCR of paired HNC tumors was performed for the phosphatases src homology domain-containing phosphatase (SHP)-1 and SHP2. Depletion of phosphatase activity in HNC and STAT1(-/-) tumor cells was achieved by siRNA knockdown. HLA class I-restricted, tumor antigen-specific CTL were used in IFN-γ ELISPOT assays against HNC cells. Chemokine secretion was measured after SHP2 depletion in HNC cells.

RESULTS

SHP2, but not SHP1, was significantly upregulated in HNC tissues. In HNC cells, SHP2 depletion significantly upregulated expression of pSTAT1 and HLA class I APM components. Overexpression of SHP2 in nonmalignant keratinocytes inhibited IFN-γ-mediated STAT1 phosphorylation, and SHP2 depletion in STAT1(-/-) tumor cells did not significantly induce IFN-γ-mediated APM component expression, verifying STAT1 dependence of SHP2 activity. SHP2 depletion induced recognition of HNC cells by HLA class I-restricted CTL and secretion of inflammatory, T-cell attracting chemokines, RANTES and IP10.

CONCLUSION

These findings suggest for the first time an important role for SHP2 in APM-mediated escape of HNC cells from CTL recognition. Targeting SHP2 could enhance T-cell-based cancer immunotherapy.

SHP-2 phosphatase promotes cervical cancer cell proliferation through inhibiting interferon-β production

AIM

The aim of this study was to explore the effect of Src-homology-2-domain-containing protein, tyrosine phosphatase 2 (SHP-2) on the proliferation of cervical cancer cells.

MATERIAL AND METHODS

A total of 45 patients with cervical cancer (stage I-III), 32 with cervical intraepithelial neoplasia and 20 healthy subjects were consecutively recruited. The levels of SHP-2 and interferon (IFN)-β expression in cervical tissues were characterized by immunohistochemistry and statistically analyzed by logistic regression. Following knockdown of SHP-2 expression by a siRNA or pre-treatment with a specific peptide, the effect of SHP-2 expression in THP-1 cells on the growth and survival of SiHa cells and on IFN-β production was determined by co-culture assays, 3-(4,5)-dimethylthiazol (-z-y 1)-3,5-diphenyltetrazolium bromide, and enzyme immunosorbent assay.

RESULTS

The levels of SHP-2 expression in cervical cancer tissues were significantly higher than that in cervical intraepithelial neoplasia and uterine myoma tissues (P<0.05, respectively), and negatively correlated with the levels of IFN-β expression in these tissues (R=-0.582, P<0.05). Knockdown of SHP-2 expression with SHP-2 siRNA or treatment with the SHP-2-specific blocking peptide in THP-1 cells significantly increased the production of IFN-β (P<0.05, respectively) and inhibited the proliferation of SiHa cells in a co-culture system of THP-1 and SiHa cells (P<0.05, respectively).

CONCLUSIONS

SHP-2 phosphatase promotes cervical cancer cell proliferation through inhibiting IFN-β production.

Different partners, opposite outcomes: a new perspective of the immunobiology of indoleamine 2,3-dioxygenase

Indoleamine 2,3-dioxygenase (IDO), a metabolic enzyme that catalyzes tryptophan conversion into kynurenines, is a crucial regulator of immunity. Altered IDO activity is often associated with pathology, including neoplasia and autoimmunity. IDO is highly expressed in dendritic cells (DCs) that exploit the enzyme's activity and the production of tryptophan catabolites to regulate immune responses by acting on several cell types, including T lymphocytes, of which they promote a regulatory phenotype. IDO also contains immunoreceptor tyrosine-based inhibitory motifs (ITIMs) that, once bound by distinct molecular partners, will either promote degradation or initiate signaling activity and self-maintenance of the enzyme. We here discuss how ITIM-dependent molecular events can affect the functional plasticity of IDO by modifying the protein half-life and its enzymic and nonenzymic functions.

SPARCL1, Shp2, MSH2, E-cadherin, p53, ADCY-2 and MAPK are prognosis-related in colorectal cancer

AIM: To investigate the expression of markers that are correlated with the prognosis of colorectal cancer (CRC) patients.

METHODS: One hundred and fifty-six CRC patients were followed up for more than 3 years after radical surgery. Immunohistochemical (IHC) analysis was performed to detect the expression of 14 pathway-related markers (p53, APC, p21ras, E-cadherin, endothelin-B receptor, Shp2, ADCY-2, SPARCL1, neuroligin1, hsp27, mmp-9, MAPK, MSH2 and rho) in specimens from these patients. Bioinformatics analysis involving a Support Vector Machine (SVM) was used to determine the best prognostic model from combinations of these markers.

RESULTS: Seven markers (SPARCL1, Shp2, MSH2, E-cadherin, p53, ADCY-2 and MAPK) were significantly related to the prognosis and clinical pathological features of the CRC patients (P < 0.05). Prognostic models were established through SVM from combinations of these 7 markers and proved able to differentiate patients with dissimilar survival, especially in stage II/III patients. According to the best prognostic model, the p53/SPARCL1 model, patients having high p53 and low SPARCL1 expression had about 50% lower 3-year survival than others (P < 0.001).

CONCLUSION: SPARCL1, Shp2, MSH2, E-cadherin, p53, ADCY-2 and MAPK are potential prognostic markers in CRC. A p53/SPARCL1 bioinformatics model may be used as a supplement to tumor-nodes-metastasis staging.

Cell surface expression of channel catfish leukocyte immune-type receptors (IpLITRs) and recruitment of both Src homology 2 domain-containing protein tyrosine phosphatase (SHP)-1 and SHP-2

Channel catfish leukocyte immune-type receptors (IpLITRs) are immunoglobulin superfamily (IgSF) members believed to play a role in the control and coordination of cellular immune responses in teleost. Putative stimulatory and inhibitory IpLITRs are co-expressed by different types of catfish immune cells (e.g. NK cells, T cells, B cells, and macrophages) but their signaling potential has not been determined. Following cationic polymer-mediated transfections into human cell lines we examined the surface expression, tyrosine phosphorylation, and phosphatase recruitment potential of two types of putative inhibitory IpLITRs using 'chimeric' expression constructs and an epitope-tagged 'native' IpLITR. We also cloned and expressed the teleost Src homology 2 domain-containing protein tyrosine phosphatases (SHP)-1 and SHP-2 and examined their expression in adult tissues and developing zebrafish embryos. Co-immunoprecipitation experiments support the inhibitory signaling potential of distinct IpLITR-types that bound both SHP-1 and SHP-2 following the phosphorylation of tyrosine residues within their cytoplasmic tail (CYT) regions. Phosphatase recruitment by IpLITRs represents an important first step in understanding their influence on immune cell effector functions and suggests that certain inhibitory signaling pathways are conserved among vertebrates.