Down-regulation of the cancer/testis antigen 45 (CT45) is associated with altered tumor cell morphology, adhesion and migration

Cancer/testis-45A1 promotes cervical cancer cell tumorigenesis and drug resistance by activating oncogenic SRC and downstream signaling pathways

BACKGROUND

Cancer/testis antigen-45A1 (CT45A1) is overexpressed in various types of cancer but is not expressed in healthy women. The role of CT45A1 in cervical cancer has not yet been described in the literature.

PURPOSE

The aim of this research was to study the role of CT45A1 in cervical cancer progression and drug resistance, elucidate the mechanisms underlying CT45A1-mediated tumorigenesis and investigate CT45A1 as a biomarker for cervical cancer diagnosis, prognostic prediction, and targeted therapy.

METHODS

The CT45A1 levels in the tumors from cervical cancer patients were measured using immunohistochemical staining. The role and mechanisms underlying CT45A1-mediated cervical cancer cell tumor growth, invasion, and drug resistance were studied using xenograft mice, cervical cancer cells, immunohistochemistry, RNA-seq, real-time qPCR, Chromatin immunoprecipitation and Western blotting.

RESULTS

CT45A1 levels were notably high in the tumor tissues of human cervical cancer patients compared to the paracancerous tissues (p < 0.001). Overexpression of CT45A1 was closely associated with poor prognosis in cervical cancer patients. CT45A1 promoted cervical cancer cell tumor growth, invasion, neovascularization, and drug resistance. Mechanistically, CT45A1 promoted the expression of 128 pro-tumorigenic genes and concurrently activated key signaling pathways, including the oncogenic SRC, ERK, CREB, and YAP/TAZ signaling pathways. Furthermore, CT45A1-mediated tumorigenesis and drug resistance were markedly inhibited by the small molecule lycorine.

CONCLUSION

CT45A1 promotes cervical cancer cell tumorigenesis, neovascularization, and drug resistance by activating oncogenic SRC and downstream tumorigenic signaling pathways. These findings provide new insight into the pathogenesis of cervical cancer and offer a new platform for the development of novel therapeutics against cervical cancer.

MUM1L1 as a Tumor Suppressor and Potential Biomarker in Ovarian Cancer: Evidence from Bioinformatics Analysis and Basic Experiments

BACKGROUND

Ovarian cancer (OC) is the most prevalent gynecologic malignancy, with high mortality rates. However, its pathogenesis remains unclear. The current study aimed to explore potential biomarkers and suppressor genes for diagnosing and treating OC.

METHODS

Biochemical and bioinformatics approaches were used to detect differentially expressed genes (DEGs) in ovarian tissues via integration analysis. Kaplan-Meier plot analysis was performed to assess progression-free survival and overall survival according to DEGs. Then, we constructed a protein-protein interaction (PPI) network based on data from the STRING database to identify the related target genes of DEGs. Finally, DEGs regulating the proliferation, migration, and invasion of SKOV3 cell lines were validated via in vitro experiments.

RESULTS

Four DEGs (MUM1L1, KLHDC8A, CRYGD, and GREB1) with enriched expression in ovarian tissues were explicitly expressed in the ovary based on an analysis of all human proteins. MUM1L1 had high specificity, and its expression was higher in normal ovarian tissues than in OC tissues. Kaplan-Meier plot analysis showed that a high MUM1L1 expression was associated with longer progression-free survival and overall survival in OC. Based on the PPI analysis results, CBLN4, CBLN1, PTH2R, TMEM255B, and COL23A1 were associated with MUM1L1. In vitro studies revealed that MUM1L1 overexpression decreased the proliferation, migration, and invasion ability of SKOV3 cell lines. Meanwhile, MUM1L1 knockdown had contrasting results.

CONCLUSION

MUM1L1 is a tumor suppressor gene and is a potential biomarker for diagnosing and treating OC.

Advances in the Lung Cancer Immunotherapy Approaches

Despite the progress in the comprehension of LC progression, risk, immunologic control, and treatment choices, it is still the primary cause of cancer-related death. LC cells possess a very low and heterogeneous antigenicity, which allows them to passively evade the anticancer defense of the immune system by educating cytotoxic lymphocytes (CTLs), tumor-infiltrating lymphocytes (TILs), regulatory T cells (Treg), immune checkpoint inhibitors (ICIs), and myeloid-derived suppressor cells (MDSCs). Though ICIs are an important candidate in first-line therapy, consolidation therapy, adjuvant therapy, and other combination therapies involving traditional therapies, the need for new predictive immunotherapy biomarkers remains. Furthermore, ICI-induced resistance after an initial response makes it vital to seek and exploit new targets to benefit greatly from immunotherapy. As ICIs, tumor mutation burden (TMB), and microsatellite instability (MSI) are not ideal LC predictive markers, a multi-parameter analysis of the immune system considering tumor, stroma, and beyond can be the future-oriented predictive marker. The optimal patient selection with a proper adjuvant agent in immunotherapy approaches needs to be still revised. Here, we summarize advances in LC immunotherapy approaches with their clinical and preclinical trials considering cancer models and vaccines and the potential of employing immunology to predict immunotherapy effectiveness in cancer patients and address the viewpoints on future directions. We conclude that the field of lung cancer therapeutics can benefit from the use of combination strategies but with comprehension of their limitations and improvements.

The expression of cancer-testis antigen in ovarian cancer and the development of immunotherapy

Ovarian cancer is a relatively common tumor in women with the highest mortality among female reproductive system tumors. The lack of apparent early symptoms and effective screening strategies often leads to ovarian cancer being diagnosed at an advanced stage. Immunotherapy relying on tumor-associated antigens might improve the treatment of ovarian cancer. Cancer-testis antigens (CTAs) are ideal tumor-associated antigens, and MAGE-A, NY-ESO-1, CT45, and Sp17 are classic CTAs highly expressed in ovarian cancer. Here, we review the research on CTAs in ovarian cancer, including prognostic value and advances in immunotherapy, all of which are essential for developing a theoretical basis for targeted therapy strategies.

Multipeptide stimulated PBMCs generate TEM/TCM for adoptive cell therapy in multiple myeloma

Multiple Myeloma (MM) patients suffer disease relapse due to the development of therapeutic resistance. Increasing evidence suggests that immunotherapeutic strategies can provide durable responses. Here we evaluate the possibility of adoptive cell transfer (ACT) by generating ex vivo T cells from peripheral blood mononuclear cells (PBMCs) isolated from MM patients by employing our previously devised protocols. We designed peptides from antigens (Ags) including cancer testis antigens (CTAs) that are over expressed in MM. We exposed PBMCs from different healthy donors (HDs) to single peptides. We observed reproducible Ag-specific cluster of differentiation 4⁺ (CD4⁺) and CD8⁺ T cell responses on exposure of PBMCs to different single peptide sequences. These peptide sequences were used to compile four different peptide cocktails. Naïve T cells from PBMCs from MM patients or HDs recognized the cognate Ag in all four peptide cocktails, leading to generation of multiclonal Ag-specific CD4⁺ and CD8⁺ effector and central memory T (T_EM and T_CM, respectively) cells which produced interferon-gamma (IFN-γ), granzyme B and perforin on secondary restimulation. Furthermore, this study demonstrated that immune cells from MM patients are capable of switching metabolic programs to induce effector and memory responses. Multiple peptides and cocktails were identified that induce IFN-γ⁺, T1-type, metabolically active T cells, thereby paving the way for feasibility testing of ACT in phase I clinical trials.

Uev1A promotes breast cancer cell migration by up-regulating CT45A expression via the AKT pathway

Background

UEV1A encodes a ubiquitin-E2 variant closely associated with tumorigenesis and metastasis, but its underlying mechanism in promoting metastasis remains to be investigated.

Methods

In this study, we experimentally manipulated UEV1A and CT45A gene expression and monitored their effects on cancer-related gene expression, cell migration and the signal transduction cascade.

Results

It was found that UEV1A overexpression induces CT45A family gene expression in breast cancer cells. Indeed, ectopic expression of UEV1A was sufficient to induce CT45A and its downstream genes involved in tumorigenesis, epithelial-mesenchymal transition (EMT), stemness and metastasis, and to promote cell migration and EMT signaling. Consistently, depletion of CT45A abolished the above effects, indicating that CT45A is a critical downstream effector of Uev1A. The Uev1A-induced cell migration and EMT signaling was dependent on AKT but independent of NF-κB, indicating that CT45A acts downstream of the AKT pathway.

Conclusions

Based on previous reports and observations in this study, we propose that the Ubc13-Uev1A complex activates AKT through K63-linked polyubiquitination, which leads to enhanced CT45A expression, stimulated cell migration and EMT signaling in breast cells. Since similar effects were also observed in a colorectal cancer cell line, the Ubc13/Uev1A-AKT-CT45A axis may also promote tumorigenesis and metastasis in other tissues.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08750-3.

CT45A1 promotes the metastasis of osteosarcoma cells in vitro and in vivo through β-catenin

Increased expression of cancer/testis antigens (CTAs) is reported in various tumors. However, the unique role of CTAs in tumor genesis has not yet been verified. Here, we first report the functional role of CT45A1 in the carcinogenesis of osteosarcoma. RNA sequencing and immunohistochemistry confirmed that elevated expression of CT45A1 was detected in osteosarcoma, especially in metastatic tissues of osteosarcoma. Furthermore, osteosarcoma patients with poorer prognosis showed high expression of CT45A1. In cell tests, CT45A1 overexpression was shown to strengthen the proliferation, migration, and invasion abilities of osteosarcoma cells, while silencing CT45A1 markedly elicited the opposite effects in these tests by disrupting the activation of β-catenin. In summary, we identify a novel role of CT45A1 in osteosarcoma. Furthermore, our results suggested that CT45A1 may contribute to the development of osteosarcoma and could be a possible therapeutic target for osteosarcoma patients.

Oncogenic cancer/testis antigens are a hallmarker of cancer and a sensible target for cancer immunotherapy

Increasing evidence shows that numerous cancer-testis antigens (CTAs) are uniquely overexpressed in various types of cancer and most CTAs are oncogenic. Overexpression of oncogenic CTAs promotes carcinogenesis, cancer metastasis, and drug resistance. Oncogenic CTAs are generally associated with poor prognosis in cancer patients and are an important hallmark of cancer, making them a crucial target for cancer immunotherapy. CTAs-targeted antibodies, vaccines, and chimeric antigen receptor-modified T cells (CAR-T) have recently been used in cancer treatment and achieved promising outcomes in the preclinical and early clinical trials. However, the efficacy of current CTA-targeted therapeutics is either moderate or low in cancer therapy. CTA-targeted cancer immunotherapy is facing enormous challenges. Several critical scientific problems need to be resolved: (1) the antigen presentation function of MHC-I protein is usually deficient in cancer patients, so that very low amounts of intracellular CTA epitopes are presented to tumor cell membrane surface, leading to weak immune response and subsequent immunity to CTAs; (2) various immunosuppressive cells are rich in tumor tissues leading to diminished tumor immunity; (3) the tumor tissue microenvironment markedly reduces the efficacy of cancer immunotherapy. In the current review paper, the authors propose new strategies and approaches to overcome the barriers of CTAs-targeted immunotherapy and to develop novel potent immune therapeutics against cancer. Finally, we highlight that the oncogenic CTAs have high tumor specificity and immunogenicity, and are sensible targets for cancer immunotherapy. We predict that CTAs-targeted immunotherapy will bring about breakthroughs in cancer therapy in the near future.

A tripartite cooperative mechanism confers resistance of the protein kinase A catalytic subunit to dephosphorylation

Phosphorylation of specific residues in the activation loops of AGC kinase group (protein kinase A, G, and C families) is required for activity of most of these kinases, including the catalytic subunit of PKA (PKAc). Although many phosphorylated AGC kinases are sensitive to phosphatase-mediated dephosphorylation, the PKAc activation loop uniquely resists dephosphorylation, rendering it "constitutively" phosphorylated in cells. Previous biophysical experiments and structural modeling have suggested that the N-terminal myristoylation signal and the C-terminal FXXF motif in PKAc regulate its thermal stability and catalysis. Here, using site-directed mutagenesis, molecular modeling, and in cell-free and cell-based systems, we demonstrate that substitutions of either the PKAc myristoylation signal or the FXXF motif only modestly reduce phosphorylation and fail to affect PKAc function in cells. However, we observed that these two sites cooperate with an N-terminal FXXW motif to cooperatively establish phosphatase resistance of PKAc while not affecting kinase-dependent phosphorylation of the activation loop. We noted that this tripartite cooperative mechanism of phosphatase resistance is functionally relevant, as demonstrated by changes in morphology, adhesion, and migration of human airway smooth muscle cells transfected with PKAc variants containing amino acid substitutions in these three sites. These findings establish that three allosteric sites located at the PKAc N and C termini coordinately regulate the phosphatase sensitivity of this enzyme. This cooperative mechanism of phosphatase resistance of AGC kinase opens new perspectives toward therapeutic manipulation of kinase signaling in disease.

CT45A1 siRNA silencing suppresses the proliferation, metastasis and invasion of lung cancer cells by downregulating the ERK/CREB signaling pathway

The aim of the present study was to investigate the role of the cancer-testis antigen family 45 member A1 (CT45A1) in the proliferation, apoptosis, invasion and metastasis of lung cancer cells, and the associated molecular mechanisms. Western blotting determined that the expression of CT45A1 in normal lung cells was far lower than that observed in lung cancer cells. Following the transfection of CT45A1 small (or short) interfering (si)RNA and its negative control into A549 cells using Lipofectamine 2000, the CT45A1 protein and mRNA levels were determined further by western blotting and reverse transcription-polymerase chain reaction. Following CT45A1 siRNA transfection, the levels of CT45A1 in lung cancer cells were markedly reduced (P<0.01). Then, cell viability and apoptosis were investigated with a methyl thiazolyl tetrazolium assay and Annexin V-FITC/propidium iodide staining, respectively. Transwell assays were employed to evaluate the migration and invasion of A549 cells. When compared with the negative control, the viability, migration and invasion of lung cancer cells treated with CT45A1 siRNA were suppressed and apoptosis was promoted (all P<0.01). In addition, the levels of B-cell lymphoma-2 (Bcl-2), Bcl-2 associated X (Bax), survivin, matrix metalloproteinase 2 (MMP2), MMP9, extracellular signal-regulated kinase 1/2 (ERK1/2), phosphorylated ERK1/2 (p-ERK1/2), cyclic AMP response element binding protein (CREB) and p-CREB were assessed by western blotting. Following CT45A1 silencing, the expressions of Bcl-2, survivin, MMP2, MMP9, p-ERK1/2 and p-CREB were downregulated and the expression of Bax was upregulated (all P<0.01). It was concluded that CT45A1 siRNA silencing suppressed the proliferation, metastasis and invasion of lung cancer cells by downregulating the ERK/CREB signalling pathway.

Expression and prognostic relevance of MAGE-A3 and MAGE-C2 in non-small cell lung cancer

Melanoma-associated antigen (MAGE)-A3 and MAGE-C2 are antigens encoded by cancer-germline genes, and have been recognized as potential prognostic biomarkers and attractive targets for immunotherapy in multiple types of cancer. The present study aimed to analyze the clinicopathological significance of MAGE-A3/C2 expression in non-small cell lung cancer (NSCLC). The association between MAGE-A3/C2 mRNA and protein expression, and the pathological characteristics and overall survival of patients with NSCLC was analyzed. In addition, the functional role of MAGE-A3 in human NSCLC cell line A549 was examined in vitro. MAGE-A3/C2 mRNA expression was identified in 73% (151/206) and 53% (109/206) of patients with NSCLC, respectively. MAGE-A3/C2 protein expression was identified in 58% (44/76) and 53% (40/76) of NSCLC cases, respectively. MAGE-A3 mRNA expression was observed to be associated with smoking history, disease stage and lymph node metastasis. However, no association was identified between MAGE-C2 mRNA expression and the clinicopathological characteristics of patients with NSCLC. MAGE-A3/C2-positive patients had a poorer survival rate compared with MAGE-A3/C2-negative patients. Multivariate analysis identified that MAGE-A3 expression may serve as an independent marker of poor prognosis in patients with NSCLC. Downregulation of MAGE-A3 mRNA expression in A549 cells resulted in lower migration and colony formation rates, and a higher amount of epithelial marker and lower amount of mesenchymal marker expression compared with the control group. These results indicate that MAGE-A3 serves a role in NSCLC cell metastasis through the induction of epithelial-mesenchymal transition. In conclusion, MAGE-A3 may serve as a diagnostic and prognostic biomarker for patients with NSCLC, due to its association with tumor progression and poor clinical outcome.

Dynamic monitoring of GPER-mediated estrogenic effects in breast cancer associated fibroblasts: An alternative role of estrogen in mammary carcinoma development

Cancer associated fibroblasts (CAFs) are crucial contributors to breast cancer development. Estrogen affects mammary stroma in both physiological and pathophysiological conditions. We show here that estrogen (G-protein coupled) receptor (GPER) could be detected by immunohistochemistry in stromal fibroblasts of primary breast cancers. The presence of GPER expression was further confirmed by immunofluorescence and quantitative PCR in CAFs isolated from primary breast cancers. Based on dynamic monitoring by real time cell analyzer (RTCA) system, 17-β-estradiol (E2) as well as GPER specific agonist G1 were observed to trigger transient cell index increasing within an hour in a dosage-dependent manner in breast CAFs. In addition, E2 and G1 stimulated intracellular calcium modulation and phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 within seconds and minutes in CAFs, respectively. Moreover, E2 and G1 promoted cell proliferation of breast CAFs measured by RTCA monitoring, cell viability assay and cell cycle analysis, and this promotion could be blocked by a GPER-selective antagonist G15. Interestingly, dynamic RTCA monitoring indicated that E2 increased adhesion of resuspended cells, and microscopy confirmed that E2 stimulated cell spreading. Both the adhesion and spreading were proposed to be mediated by GPER, since G1 also stimulated these effects similar to E2, and G15 reduced them. Moreover, GPER was found to mediate migration that was increased by E2 and G1 but reduced by G15 in RTCA cell migration assay and transwell assay. Accordingly, GPER mediates not only rapid actions but also slow effects including adhesion/spreading, proliferation and migration in breast CAFs. Estrogen is likely to affect tumor associated stroma and contributes to mammary carcinoma development through CAFs.

DNA hypomethylation-mediated activation of Cancer/Testis Antigen 45 (CT45) genes is associated with disease progression and reduced survival in epithelial ovarian cancer

Epithelial ovarian cancer (EOC) is a highly lethal malignancy due to a lack of early detection approaches coupled with poor outcomes for patients with clinically advanced disease. Cancer-testis (CT) or cancer-germline genes encode antigens known to generate spontaneous anti-tumor immunity in cancer patients. CT45 genes are a recently discovered 6-member family of X-linked CT genes with oncogenic function. Here, we determined CT45 expression in EOC and fully defined its epigenetic regulation by DNA methylation. CT45 was silent and hypermethylated in normal control tissues, but a large subset of EOC samples showed increased CT45 expression in conjunction with promoter DNA hypomethylation. In contrast, copy number status did not correlate with CT45 expression in the TCGA database for EOC. CT45 promoter methylation inversely correlated with both CT45 mRNA and protein expression, the latter determined using IHC staining of an EOC TMA. CT45 expression was increased and CT45 promoter methylation was decreased in late-stage and high-grade EOC, and both measures were associated with poor survival. CT45 hypomethylation was directly associated with LINE-1 hypomethylation, and CT45 was frequently co-expressed with other CT antigen genes in EOC. Decitabine treatment induced CT45 mRNA and protein expression in EOC cells, and promoter transgene analyses indicated that DNA methylation directly represses CT45 promoter activity. These data verify CT45 expression and promoter hypomethylation as possible prognostic biomarkers, and suggest CT45 as an immunological or therapeutic target in EOC. Treatment with decitabine or other epigenetic modulators could provide a means for more effective immunological targeting of CT45.

Combined cancer testis antigens enhanced prediction accuracy for prognosis of patients with hepatocellular carcinoma

Cancer testis antigens (CTAs) are selectively expressed in malignant cells and can serve as ideal targets for immunotherapy. We investigated the expressions of MAGE-A3, MAGE-A4, MAGE-C2 and NY-ESO-1 to determine if combinatorial expressions of CTAs might be as potential prognostic markers for patients with hepatocellular carcinoma (HCC). In tumor tissues of 142 HCC patients, the mRNA expressions of MAGE-A3, MAGE-A4, MAGE-C2 and NY-ESO-1 were 78.9%, 33.8%, 74.6% and 14.1% respectively. Furthermore, the expressions of MAGE-A3, MAGE-A4 and combination of MAGE-A3, MAGE-A4 and NY-ESO-1 (CTAs-A3/A4/NY) showed positive correlations with serum AFP, tumor stages and Ki-67 (P < 0.05). In addition, mRNA expressions of CTAs were significantly consistent with protein expressions of CTAs by immunohistochemistry (P > 0.05). Receiver operating characteristic curves (ROC) analysis showed that CTAs-A3/A4/NY had larger areas under ROC curve (0.768), specificity (99.1%), Youden's index (44.6), positive predictive value (90.9%) and negative predictive value (89.9%) for predicting HCC recurrence than other CTAs. Moreover, the combinatorial expression of CTAs-A3/A4/NY was significantly associated with HCC recurrence by Kaplan-Meier analysis (HR = 69.36, P < 0.01) and multivariate Cox analysis (RR = 17.11, P < 0.01). The combinatorial expression of CTAs-A3/A4/NY mRNA promotes the predictive accuracy of HCC recurrence and itself may be a potential target for immunotherapy of HCC as well.

Cancer-testis genes as candidates for immunotherapy in breast cancer

Cancer-testis (CT) antigens are tumor-associated antigens attracting immunologists for their possible application in the immunotherapy of cancer. Several clinical trials have assessed their therapeutic potentials in cancer patients. Breast cancers, especially triple-negative cancers are among those with significant expression of CT genes. Identification of CT genes with high expression in cancer patients is the prerequisite for any immunotherapeutic approach. CT genes have gained attention not only for immunotherapy of cancer patients, but also for immunoprevention in high-risk individuals. Many CT genes have proved to be immunogenic in breast cancer patients suggesting the basis for the development of polyvalent vaccines.

Effects of size and surface of zinc oxide and aluminum-doped zinc oxide nanoparticles on cell viability inferred by proteomic analyses

Although the health effects of zinc oxide nanoparticles (ZnONPs) on the respiratory system have been reported, the fate, potential toxicity, and mechanisms in biological cells of these particles, as related to particle size and surface characteristics, have not been well elucidated. To determine the physicochemical properties of ZnONPs that govern cytotoxicity, we investigated the effects of size, electronic properties, zinc concentration, and pH on cell viability using human alveolar-basal epithelial A549 cells as a model. We observed that a 2-hour or longer exposure to ZnONPs induced changes in cell viability. The alteration in cell viability was associated with the zeta potentials and pH values of the ZnONPs. Proteomic profiling of A549 exposed to ZnONPs for 2 and 4 hours was used to determine the biological mechanisms of ZnONP toxicity. p53-pathway activation was the core mechanism regulating cell viability in response to particle size. Activation of the Wnt and TGFβ signaling pathways was also important in the cellular response to ZnONPs of different sizes. The cadherin and Wnt signaling pathways were important cellular mechanisms triggered by surface differences. These results suggested that the size and surface characteristics of ZnONPs might play an important role in their observed cytotoxicity. This approach facilitates the design of more comprehensive systems for the evaluation of nanoparticles.

Role of Bruton's tyrosine kinase (BTK) in growth and metastasis of INA6 myeloma cells

Bruton's tyrosine kinase (BTK) and the chemokine receptor CXCR4 are linked in various hematologic malignancies. The aim of the study was to understand the role of BTK in myeloma cell growth and metastasis using the stably BTK knockdown luciferase-expressing INA6 myeloma line. BTK knockdown had reduced adhesion to stroma and migration of myeloma cells toward stromal cell-derived factor-1. BTK knockdown had no effect on short-term in vitro growth of myeloma cells, although clonogenicity was inhibited and myeloma cell growth was promoted in coculture with osteoclasts. In severe combined immunodeficient-rab mice with contralaterally implanted pieces of bones, BTK knockdown in myeloma cells promoted their proliferation and growth in the primary bone but suppressed metastasis to the contralateral bone. BTK knockdown myeloma cells had altered the expression of genes associated with adhesion and proliferation and increased mammalian target of rapamycin signaling. In 176 paired clinical samples, BTK and CXCR4 expression was lower in myeloma cells purified from a focal lesion than from a random site. BTK expression in random-site samples was correlated with proportions of myeloma cells expressing cell surface CXCR4. Our findings highlight intratumoral heterogeneity of myeloma cells in the bone marrow microenvironment and suggest that BTK is involved in determining proliferative, quiescent or metastatic phenotypes of myeloma cells.

CT45A1 acts as a new proto-oncogene to trigger tumorigenesis and cancer metastasis

Cancer/testis antigen (CTA)-45 family (CT45) belongs to a new family of genes in phylogenetics and is absent in normal tissues except for testis, but is aberrantly overexpressed in various cancer types. Whether CT45 and other CTAs act as proto-oncogenes has not been determined. Using breast cancer as a model, we found that CT45A1, a representative CT45 family member, alone had a weak tumorigenic effect. However, its neoplastic potency was greatly enhanced in the presence of growth factors. Overexpression of CT45A1 in breast cancer cells markedly upregulated various oncogenic and metastatic genes, constitutively activated ERK and CREB signaling pathways, promoted epithelial-mesenchymal transition, and increased cell stemness, tumorigenesis, invasion, and metastasis, whereas silencing CT45A1 significantly reduced cancer cell migration and invasion. We propose that CT45A1 functions as a novel proto-oncogene to trigger oncogenesis and metastasis. CT45A1 and other CT45 members are therefore excellent targets for anticancer drug discovery and targeted tumor therapy, and valuable genes in the study of a molecular phylogenetic tree.