B-MYB positively regulates serine-threonine kinase receptor-associated protein (STRAP) activity through direct interaction

Downstream Regulatory Network of MYBL2 Mediating Its Oncogenic Role in Melanoma

The transcription factor MYBL2 is widely expressed in proliferating cells. Aberrant expression of MYBL2 contributes to tumor malignancy and is associated with poor patient prognosis. However, the downstream transcriptional network that mediates its oncogenic properties remains elusive. In the present study, we observed that MYBL2 was overexpressed in malignant and metastatic melanoma patient samples and that the high expression level of MYBL2 was significantly associated with poor prognosis. A loss-of-function study demonstrated that MYBL2 depletion significantly decreased cell proliferation and migration and prevented cell cycle progression. We also determined that MYBL2 promoted the formation of melanoma stem-like cell populations, indicating its potential as a therapeutic target for treating resistant melanoma. Mechanistically, we constructed an MYBL2 regulatory network in melanoma by integrating RNA-seq and ChIP-seq data. EPPK1, PDE3A, and FCGR2A were identified as three core target genes of MYBL2. Importantly, multivariate Cox regression and survival curve analysis revealed that PDE3A and EPPK1 were negatively correlated with melanoma patient survival; however, FCGR2A was positively correlated with patient survival. Overall, our findings elucidate an MYBL2 regulatory network related to cell proliferation and cancer development in melanoma, suggesting that MYBL2 may be potentially targeted for melanoma diagnosis and treatment.

Actin-binding Rho activating C-terminal like (ABRACL) transcriptionally regulated by MYB proto-oncogene like 2 (MYBL2) promotes the proliferation, invasion, migration and epithelial-mesenchymal transition of breast cancer cells

Breast cancer is the most common malignant tumor in females with high incidence and mortality. Actin-binding Rho activating C-terminal like (ABRACL) was highly expressed in several cancers. We aimed to investigate the function and mechanism of ABRACL in breast cancer. In this study, biological information analysis predicted the expression of ABRACL and MYB proto-oncogene-like 2 (MYBL2) in breast cancer tissues and their possible relationship. With the application of RT-qPCR and western blot, the mRNA and protein expression of ABRACL and MYBL2 in breast cancer cell lines were assessed. After ABRACL interference, an assessment of cell proliferation was carried out using cell counting kit (CCK)-8, colony formation, and western blot. The invasive and migratory abilities of cells were determined by transwell and wound healing assays. The epithelial-mesenchymal transition (EMT) process was assayed utilizing western blot. The relationship between ABRACL and MYBL2 was confirmed by luciferase reporter assay and chromatin immunoprecipitation (ChIP). The above experiments were done again after MYBL2 overexpression in breast cancer cells with ABRACL deletion. Results revealed that ABRACL and MYBL2 were highly expressed in breast cancer tissues and cells. ABRACL knockdown suppressed the proliferation, invasion, migration, and EMT of breast cancer cells. MYBL2 transcriptionally activated ABRACL. Besides, MYBL2 overexpression reversed the effects of ABRACL knockdown on cell malignant biological behaviors. To conclude, ABRACL could be transcriptionally regulated by MYBL2 to promote cell malignant biological behaviors in breast cancer cells, implying the potential of ABRACL being a promising target for the improvement of breast cancer therapy.

Single-cell transcriptomics reveal DHX9 in mature B cell as a dynamic network biomarker before lymph node metastasis in CRC

Increasing evidence indicates that mature B cells in the adjacent tumor tissue, both as an intermediate state, are vital in advanced colorectal cancer (CRC), which is associated with a low survival rate. Developing predictive biomarkers that detect the tipping point of mature B cells before lymph node metastasis in CRC is critical to prevent irreversible deterioration. We analyzed B cells in the adjacent tissues of CRC samples from different stages using the dynamic network biomarker (DNB) method. Single-cell profiling of 725 CRC-derived B cells revealed the emergence of a mature B cell subtype. Using the DNB method, we identified stage II as a critical period before lymph node metastasis and that reversed difference genes triggered by DNBs were enriched in the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway involving B cell immune capability. DHX9 (DEAH-box helicase 9) was a specific para-cancerous tissue DNB key gene. The dynamic expression levels of DHX9 and its proximate network genes involved in B cell-related pathways were reversed at the network level from stage I to III. In summary, DHX9 in mature B cells of CRC-adjacent tissues may serve as a predictable biomarker and a potential immune target in CRC progression.

The role of MYB proto-oncogene like 2 in tamoxifen resistance in breast cancer

Despite the efficacy of tamoxifen in preventing disease relapse, a large portion of breast cancer patients show intrinsic or acquired resistance to tamoxifen, leading to treatment failure and unfavorable clinical outcome. MYB proto-oncogene like 2 (MYBL2) is a transcription factor implicated in the initiation and progression of various human cancers. However, its role in tamoxifen resistance in breast cancer remained largely unknown. In the present study, by analyzing public transcriptome dataset, we found that MYBL2 is overexpressed in breast cancer and is associated with the poor prognosis of breast cancer patients. By establishing tamoxifen-resistant breast cancer cell lines, we also provided evidence that MYBL2 overexpression contributes to tamoxifen resistance by up-regulating its downstream transcriptional effectors involved in cell proliferation (PLK1, PRC1), survival (BIRC5) and metastasis (HMMR). In contrast, inhibiting those genes via MYBL2 depletion suppresses cancer progression, restores tamoxifen and eventually reduces the risk of disease recurrence. All these findings revealed a critical role of MYBL2 in promoting tamoxifen resistance and exacerbating the progression of breast cancer, which may serve as a novel therapeutic target to overcome drug resistance and improve the prognosis of breast cancer patients.

B-MYB-p53-related relevant regulator for the progression of clear cell renal cell carcinoma

PURPOSE

To investigate the mRNA expression of B-MYB and MDM2 together with their p53 relatedness in clear cell renal cell carcinoma (ccRCC).

METHODS

Genes were screened for their mRNA expression from 529 patients in a publicly available ccRCC cohort (TCGA). A cohort of 101 patients with ccRCC served as validation by qRT-PCR mRNA tissue expression analysis.

RESULTS

Expression: B-MYB expression was significantly higher in high-grade tumours (p < 0.0001 and p = 0.048) and in advanced stages (p = 0.005 and p = 0.037) in both cohorts. Correlation: p53-B-MYB as well as MDM2-B-MYB showed significant correlations in local and low-grade ccRCCs, but not in high grade tumours or advanced stages (r < 0.3 and/or p > 0.05). Survival: Multivariable Cox regression of the TCGA cohort revealed B-MYB upregulation and low MDM2 expression as predictors for an impaired overall survival (OS) (HR 1.97; p = 0.0003; HR 2.94, p < 0.0001) and progression-free survival (PFS) (HR 2.86; p = 0.0005; HR 1.58, p = 0.046). In the validation cohort, the results were confirmed for OS by univariable, but not multivariable regression: high B-MYB expression (HR = 3.05, p = 0.035) and low MDM2 expression (HR 3.81, p value 0.036).

CONCLUSION

In ccRCC patients with high-grade tumours and advanced stages, high B-MYB expression is common and is associated with poorer OS and PFS. These patients show a loss of their physiological B-MYB-p53 network correlation, suggesting an additional, alternative regulatory, oncogenic mechanism. Assuming further characterization of its signalling pathways, B-MYB could be a potential therapy target for ccRCC.

SIRT7 Deacetylates STRAP to Regulate p53 Activity and Stability

Serine-threonine kinase receptor-associated protein (STRAP) functions as a regulator of both TGF-β and p53 signaling that participates in the regulation of cell proliferation and cell death in response to various stresses. Here, we demonstrate that STRAP acetylation plays an important role in p53-mediated cell cycle arrest and apoptosis. STRAP is acetylated at lysines 147, 148, and 156 by the acetyltransferases CREB-binding protein (CBP) and that the acetylation is reversed by the deacetylase sirtuin7 (SIRT7). Hypo- or hyperacetylation mutations of STRAP at lysines 147, 148, and 156 (3KR or 3KQ) influence its activation and stabilization of p53. Moreover, following 5-fluorouracil (5-FU) treatment, STRAP is mobilized from the cytoplasm to the nucleus and promotes STRAP acetylation. Our finding on the regulation of STRAP links p53 with SIRT7 influencing p53 activity and stability.

Cathepsin L induced PC-12 cell apoptosis via activation of B-Myb and regulation of cell cycle proteins

Cathepsin L (CTSL), a cysteine protease, is responsible for the degradation of a variety of proteins. It is known to participate in neuronal apoptosis associated with abnormal cell cycle. However, the mechanisms underlying CTSL-induced cell apoptosis remain largely unclear. We reported here that rotenone caused an activation of CTSL expression in PC-12 cells, while knockdown of CTSL by small interfering RNAs or its inhibitor reduced the rotenone-induced cell cycle arrest and apoptosis. Moreover, elevation of CTSL and increased-apoptosis were accompanied by induction of B-Myb, a crucial cell cycle regulator. We found that B-Myb was increased in rotenone-treated PC-12 cells and knockdown of B-Myb ameliorated rotenone-stimulated cell apoptosis. Further analysis demonstrated that CTSL influenced the expression of B-Myb as suppression of CTSL activity led to a decreased B-Myb expression, whereas overexpression of CTSL resulted in B-Myb induction. Reduction of B-Myb in CTSL-overexpressing cells revealed that regulation of cell cycle-related proteins, including cyclin A and cyclin B1, through CTSL was mediated by the transcription factor B-Myb. In addition, we demonstrated that the B-Myb target, Bim, and its regulator, Egr-1, which was also associated with CTSL closely, were both involved in rotenone-induced apoptosis in PC-12 cells. Our data not only revealed the role of CTSL in rotenone-induced neuronal apoptosis, but also indicated the involvement of B-Myb in CTSL-related cell cycle regulation.

Dual Roles of Serine-Threonine Kinase Receptor-Associated Protein (STRAP) in Redox-Sensitive Signaling Pathways Related to Cancer Development

Serine-threonine kinase receptor-associated protein (STRAP) is a transforming growth factor β (TGF-β) receptor-interacting protein that has been implicated in both cell proliferation and cell death in response to various stresses. However, the precise roles of STRAP in these cellular processes are still unclear. The mechanisms by which STRAP controls both cell proliferation and cell death are now beginning to be unraveled. In addition to its biological roles, this review also focuses on the dual functions of STRAP in cancers displaying redox dysregulation, where it can behave as a tumor suppressor or an oncogene (i.e., it can either inhibit or promote tumor formation), depending on the cellular context. Further studies are needed to define the functions of STRAP and the redox-sensitive intracellular signaling pathways that enhance either cell proliferation or cell death in human cancer tissues, which may help in the development of effective treatments for cancer.

MYBL2 (B-Myb): a central regulator of cell proliferation, cell survival and differentiation involved in tumorigenesis

Limitless cell proliferation, evasion from apoptosis, dedifferentiation, metastatic spread and therapy resistance: all these properties of a cancer cell contribute to its malignant phenotype and affect patient outcome. MYBL2 (alias B-Myb) is a transcription factor of the MYB transcription factor family and a physiological regulator of cell cycle progression, cell survival and cell differentiation. When deregulated in cancer cells, MYBL2 mediates the deregulation of these properties. In fact, MYBL2 is overexpressed and associated with poor patient outcome in numerous cancer entities. MYBL2 and players of its downstream transcriptional network can be used as prognostic and/or predictive biomarkers as well as potential therapeutic targets to offer less toxic and more specific anti-cancer therapies in future. In this review, we summarize current knowledge on the physiological roles of MYBL2 and highlight the impact of its deregulation on cancer initiation and progression.

Synchronous alteration pattern between serine-threonine kinase receptor-associated protein and Smad7 in pilocarpine-induced rats of epilepsy

PURPOSE

Recent studies have shown that transforming growth factor β (TGFβ) signaling participates in the epileptogenesis. Serine-threonine kinase receptor-associated protein (STRAP) and Smad7 synergize in the inhibition of the TGFβ signaling. The aim of the present study was to determine the expression pattern of STRAP and Smad7 in the hippocampus and temporal lobe cortex of pilocarpine-induced rats models of epilepsy.

METHODS

Lithium chloride-pilocarpine-induced rats with status epilepticus (SE) were established. Total of 60 male Sprague-Dawley rats was used as control (n = 10), 24 h (n = 10), 72 h (n = 10), 1 week (n = 10), 1 month (n = 10), and 2 months (n = 10) after pilocarpine-induced SE, respectively. We detected the expression levels of STRAP and Smad7 in the hippocampus and temporal lobe cortex of rats at the aforementioned time points using western blotting and immunohistochemistry.

RESULTS

STRAP level was significantly decreased in 24 h, 72 h (acute stage), 1 week (latent stage), 1 month, 2 months (chronic stage), respectively, in the rat models compared with the control rats by using both western blotting and immunohistochemistry. Smad7 had similar reduced pattern as STRAP.

CONCLUSIONS

Our results indicate that STRAP and Smad7 proteins might be involved in the development of temporal lobe epilepsy.

Proteomic analysis of proton beam irradiated human melanoma cells

Proton beam irradiation is a form of advanced radiotherapy providing superior distributions of a low LET radiation dose relative to that of photon therapy for the treatment of cancer. Even though this clinical treatment has been developing for several decades, the proton radiobiology critical to the optimization of proton radiotherapy is far from being understood. Proteomic changes were analyzed in human melanoma cells treated with a sublethal dose (3 Gy) of proton beam irradiation. The results were compared with untreated cells. Two-dimensional electrophoresis was performed with mass spectrometry to identify the proteins. At the dose of 3 Gy a minimal slowdown in proliferation rate was seen, as well as some DNA damage. After allowing time for damage repair, the proteomic analysis was performed. In total 17 protein levels were found to significantly (more than 1.5 times) change: 4 downregulated and 13 upregulated. Functionally, they represent four categories: (i) DNA repair and RNA regulation (VCP, MVP, STRAP, FAB-2, Lamine A/C, GAPDH), (ii) cell survival and stress response (STRAP, MCM7, Annexin 7, MVP, Caprin-1, PDCD6, VCP, HSP70), (iii) cell metabolism (TIM, GAPDH, VCP), and (iv) cytoskeleton and motility (Moesin, Actinin 4, FAB-2, Vimentin, Annexin 7, Lamine A/C, Lamine B). A substantial decrease (2.3 x) was seen in the level of vimentin, a marker of epithelial to mesenchymal transition and the metastatic properties of melanoma.