Mutant p53 (p53-R248Q) functions as an oncogene in promoting endometrial cancer by up-regulating REGγ

Multi-omics profiling reveal cells with novel oncogenic cluster, TRAP1low/CAMSAP3low, emerge more aggressive behavior and poor-prognosis in early-stage endometrial cancer

The clinical heterogeneity of early-stage endometrial cancer (EC) is worthy of further study to identify high-quality prognostic markers and their potential role in aggressive tumor behavior. Mutation of TP53 was considered as an important primary triage in modified molecular typing for EC, it still cannot precisely predict the prognosis of EC. After proteomic analysis of cancer and para-cancerous tissues from 24 early-stage endometrioid EC patients with different survival outcomes, 13 differentially expressed proteins were screen out while 2 proteins enriched in p53 signaling pathway were further identified by single-cell transcriptome (scRNA-seq). Interestingly, tumor necrosis factor type-1 receptor-associated protein (TRAP1) and calmodulin-regulated spectrin-associated protein family member 3 (CAMSAP3) were found to be significantly downregulated in the specific cell cluster. Expectedly, the signature genes of TRAP1low/CAMSAP3low cluster included classical oncogenes. Moreover, close cellular interactions were observed between myeloid cells and the TRAP1low/CAMSAP3low cluster after systematically elucidating their relationship with tumor microenvironment (TME). The expression of TRAP1 and CAMSAP3 was verified by immunohistochemistry. Thus, a novel prediction model combining TRAP1, CAMSAP3 and TP53 was construct by multi-omics. Compared with the area under the curve, it demonstrated a significantly improvemrnt in the diagnostic efficacy in EC patients from TCGA bank. In conclusion, this work improved the current knowledge regarding the prognosis of early-stage EC through proteomics and scRNA-seq. These findings may lead to improvements in precise risk stratification of early-stage EC patients.

TP53R175H mutation promotes breast cancer cell proliferation through CORO1A-P38 MAPK pathway regulation

Breast cancer is the most commonly diagnosed cancer in women. Among all types, triple-negative breast cancer is particularly challenging to cure because of its high recurrence rates and invasive and metastatic capacity. Although numerous studies have explored the role of TP53 mutations in cancer, there is a dearth of research regarding the correlation between TP53 mutations and breast cancer cell proliferation. In this study, our aim was to examine the impact of TP53 mutations on the prognosis of patients with breast cancer bioinformatics techniques. To detect cell proliferation, a CCK8 assay was performed, and western blotting was used to identify the expression of p53, p38, and p-p38 proteins. Cellular mRNA sequencing was used to screen target genes of TP53 mutations, and molecular docking was performed to identify the drugs that could hinder the proliferation of breast cancer cells.The results showed that the TP53 mutation rate is higher in patients with triple-negative breast cancer than non-triple-negative breast cancer, and those with TP53 mutations tended to have a poorer prognosis than those without. Patients with R175H site mutations also had shorter survival times than those without. Cytological experiments revealed that the TP53R175H mutation increases the rate of breast cancer cell proliferation. In conjunction with this, CORO1A was found to be a downstream target of TP53 mutations, and it was determined to promote breast cancer cell proliferation. Moreover, CORO1A overexpression resulted in the downregulation of p-p38 levels. Molecular docking studies further revealed that tea polyphenols can inhibit breast cancer proliferation by binding to p53.

TBBPA rather than its main derivatives enhanced growth of endometrial cancer via p53 ubiquitination

Tetrabromobisphenol A (TBBPA) and its derivatives widely exist in various environments and biota. Although the available data indicate that TBBPA exposure is highly associated with the increased incidence of endometrial cancer (EC), the effects of TBBPA and its main derivatives on EC proliferation and the involved crucial mechanism remain unclear. The present study aimed to investigate the effects of TBBPA and its derivatives under environmental concentrations on the proliferation of EC, and the crucial mechanism on the progression of EC caused by bromine flame retardants exposure. In this research, TBBPA and two of the most common TBBPA derivatives including TBBPA bis (2-hydroxyethyl ether) (TBBPA-BHEE) and TBBPA bis (dibromopropyl ether) (TBBPA-BDBPE) were screened for their capacities in induced EC proliferation and explored the related mechanism by in vitro cell culture model and in vivo mice model. Under environmental concentrations, TBBPA promoted the proliferation of EC, the main derivatives of TBBPA (TBBPA-BHEE and TBBPA-BDBPE) did not present the similar facilitation effects. The ubiquitination degradation of p53 was crucial in TBBPA induced EC proliferation, which resulted in the increase of downstream cell cycle and decrease of apoptosis. The further molecular docking result suggested the high affinity between TBBPA and ubiquitinated proteasome. This finding revealed the effects of TBBPA and its derivatives on EC proliferation, thus providing novel insights into the underlying mechanisms of TBBPA-caused EC.

Mutant p53R211* ameliorates inflammatory arthritis in AIA rats via inhibition of TBK1-IRF3 innate immune response

BACKGROUND

Rheumatoid arthritis (RA) is an autoimmune inflammation disease characterized by imbalance of immune homeostasis. p53 mutants are commonly described as the guardian of cancer cells by conferring them drug-resistance and immune evasion. Importantly, p53 mutations have also been identified in RA patients, and this prompts the investigation of its role in RA pathogenesis.

METHODS

The cytotoxicity of disease-modifying anti-rheumatic drugs (DMARDs) against p53 wild-type (WT)/mutant-transfected RA fibroblast-like synoviocytes (RAFLSs) was evaluated by MTT assay. Adeno-associated virus (AAV) was employed to establish p53 WT/R211* adjuvant-induced arthritis (AIA) rat model. The arthritic condition of rats was assessed by various parameters such as micro-CT analysis. Knee joint samples were isolated for total RNA sequencing analysis. The expressions of cytokines and immune-related genes were examined by qPCR, ELISA assay and immunofluorescence. The mechanistic pathway was determined by immunoprecipitation and Western blotting in vitro and in vivo.

RESULTS

Among p53 mutants, p53R213* exhibited remarkable DMARD-resistance in RAFLSs. However, AAV-induced p53R211* overexpression ameliorated inflammatory arthritis in AIA rats without Methotrexate (MTX)-resistance, and our results discovered the immunomodulatory effect of p53R211* via suppression of T-cell activation and T helper 17 cell (Th17) infiltration in rat joint, and finally downregulated expressions of pro-inflammatory cytokines. Total RNA sequencing analysis identified the correlation of p53R211* with immune-related pathways. Further mechanistic studies revealed that p53R213*/R211* instead of wild-type p53 interacted with TANK-binding kinase 1 (TBK1) and suppressed the innate immune TBK1-Interferon regulatory factor 3 (IRF3)-Stimulator of interferon genes (STING) cascade.

CONCLUSIONS

This study unravels the role of p53R213* mutant in RA pathogenesis, and identifies TBK1 as a potential anti-inflammatory target.

Current insights into the regulation of programmed cell death by TP53 mutation in cancer

Gene mutation is a complicated process that influences the onset and progression of cancer, and the most prevalent mutation involves the TP53 gene. One of the ways in which the body maintains homeostasis is programmed cell death, which includes apoptosis, autophagic cell death, pyroptosis, ferroptosis, NETosis, and the more recently identified process of cuprotosis. Evasion of these cell deaths is a hallmark of cancer cells, and our elucidation of the way these cells die helps us better understands the mechanisms by which cancer arises and provides us with more ways to treat it.Studies have shown that programmed cell death requires wild-type p53 protein and that mutations of TP53 can affect these modes of programmed cell death. For example, mutant p53 promotes iron-dependent cell death in ferroptosis and inhibits apoptotic and autophagic cell death. It is clear that TP53 mutations act on more than one pathway to death, and these pathways to death do not operate in isolation. They interact with each other and together determine cell death. This review focuses on the mechanisms via which TP53 mutation affects programmed cell death. Clinical investigations of TP53 mutation and the potential for targeted pharmacological agents that can be used to treat cancer are discussed.

Regulation of Life & Death by REGγ

REGγ, a proteasome activator belonging to the 11S (otherwise known as REG, PA28, or PSME) proteasome activator family, is widely present in many eukaryotes. By binding to the 20S catalytic core particle, REGγ acts as a molecular sieve to selectively target proteins for degradation in an ATP- and ubiquitin-independent manner. This non-canonical proteasome pathway directly regulates seemingly unrelated cellular processes including cell growth and proliferation, apoptosis, DNA damage response, immune response, and metabolism. By affecting different pathways, REGγ plays a vital role in the regulation of cellular life and death through the maintenance of protein homeostasis. As a promoter of cellular growth and a key regulator of several tumor suppressors, many recent studies have linked REGγ overexpression with tumor formation and suggested the REGγ-proteasome as a potential target of new cancer-drug development. This review will present an overview of the major functions of REGγ as it relates to the regulation of cellular life and death, along with new mechanistic insights into the regulation of REGγ.

Cancer-related Mutations with Local or Long-range Effects on an Allosteric Loop of p53

The tumor protein 53 (p53) is involved in transcription-dependent and independent processes. Several p53 variants related to cancer have been found to impact protein stability. Other variants, on the contrary, might have little impact on structural stability and have local or long-range effects on the p53 interactome. Our group previously identified a loop in the DNA binding domain (DBD) of p53 (residues 207-213) which can recruit different interactors. Experimental structures of p53 in complex with other proteins strengthen the importance of this interface for protein-protein interactions. We here characterized with structure-based approaches somatic and germline variants of p53 which could have a marginal effect in terms of stability and act locally or allosterically on the region 207-213 with consequences on the cytosolic functions of this protein. To this goal, we studied 1132 variants in the p53 DBD with structure-based approaches, accounting also for protein dynamics. We focused on variants predicted with marginal effects on structural stability. We then investigated each of these variants for their impact on DNA binding, dimerization of the p53 DBD, and intramolecular contacts with the 207-213 region. Furthermore, we identified variants that could modulate long-range the conformation of the region 207-213 using a coarse-grain model for allostery and all-atom molecular dynamics simulations. Our predictions have been further validated using enhanced sampling methods for 15 variants. The methodologies used in this study could be more broadly applied to other p53 variants or cases where conformational changes of loop regions are essential in the function of disease-related proteins.

MicroRNA expression profile in serum reveals novel diagnostic biomarkers for endometrial cancer

Purpose: Circulating microRNAs (miRNAs) prove to be promising diagnostic biomarkers for various cancers, including endometrial cancer (EC). The present study aims to identify serum microRNAs that can serve as potential biomarkers for EC diagnosis.

Patients and methods: A total of 92 EC and 102 normal control (NC) serum samples were analyzed using quantitative real-time polymerase chain reaction (qRT-PCR) in this four-phase experiment. The logistic regression method was used to construct a diagnostic model based on the differentially expressed miRNAs in serum. The receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic value. To further validate the diagnostic capacity of the identified signature, the 6-miRNA marker was compared with previously reported biomarkers and verified in three public datasets. In addition, the expression characteristics of the identified miRNAs were further explored in tissue and serum exosomes samples.

Results: Six miRNAs (miR-143-3p, miR-195-5p, miR-20b-5p, miR-204-5p, miR-423-3p, and miR-484) were significantly overexpressed in the serum of EC compared with NCs. Areas under the ROC of the 6-miRNA signatures were 0.748, 0.833, and 0.967 for the training, testing, and the external validation phases, respectively. The identified signature has a very stable diagnostic performance in the large cohorts of three public datasets. Compared with previously identified miRNA biomarkers, the 6-miRNA signature in the present study has superior performance in diagnosing EC. Moreover, the expression of miR-143-3p and miR-195-5p in tissues and the expression of miR-20b-5p in serum exosomes were consistent with those in serum.

Conclusions: We established a 6-miRNA signature in serum and they could function as potential non-invasive biomarker for EC diagnosis.

High expression of Rab31 confers a poor prognosis and enhances cell proliferation and invasion in oral squamous cell carcinoma

Dysregulation of Rab proteins has been observed in various types of cancer. Ectopic expression of Rab31, a member of the Rab protein family, is involved in cancer development and progression. However, the specific role and potential molecular mechanism underlying the functions of Rab31 remain largely unknown. Therefore, the current study aimed to investigate the functions of Rab31 in the development of cancer. Human oral squamous cell carcinoma (OSCC) samples were examined to determine the expression profile of Rab31 and its association with the clinicopathological characteristics of patients with OSCC. Knockdown of Rab31 expression with short hairpin RNA was performed to analyze the functions of Rab31 in vitro and in vivo. The expression of Rab31 was significantly elevated in human OSCC samples compared with that in normal oral mucosal epithelial tissues, and high expression levels were associated with high pathological grades. Furthermore, positive expression of Rab31 was associated with a poor prognosis in patients with OSCC. In addition, knockdown of Rab31 expression suppressed OSCC cell proliferation and induced apoptosis compared with those in the control‑transfected cells, which may have been caused by downregulated cyclin D1 and survivin expression and upregulated B‑cell lymphoma 2 expression. The invasive ability of OSCC cells was also abrogated by Rab31 silencing compared with that in the control‑transfected cells, which was associated with downregulated N‑cadherin and matrix metalloproteinase‑9 expression levels and upregulated levels of E‑cadherin expression. Furthermore, silencing Rab31 in OSCC cell lines, when compared with the control‑transfected cells, significantly reduced tumor growth and inhibited the expression of survivin, Ki‑67 and N‑cadherin in vivo. By contrast, the expression levels of E‑cadherin were increased. Taken together, the results of the present study supported important roles for Rab31 in regulating OSCC cell proliferation, apoptosis and invasion and may facilitate the identification of a new therapeutic target for the treatment of OSCC.

Construction of a nine DNA repair-related gene prognostic classifier to predict prognosis in patients with endometrial carcinoma

Background

Endometrial cancer (EC) is one of the most common gynecological malignancies worldwide. However, the molecular mechanisms and the prognostic prediction for EC patients remain unclear.

Methods

In the current study, we performed an in-depth analysis of over 500 patients which were obtained from the Cancer Genome Atlas (TCGA) database. The bioinformatics analysis included gene set enrichment analysis (GSEA) and Cox and lasso regression analyses to ensure overall survival (OS)-related genes, moreover, to construct a prognostic model and a nomogram for EC patients.

Results

GSEA identified 4 gene sets significantly associated with EC, which are DNA repair, unfolded protein response, reactive oxygen species pathway and UV response up. Twenty-five OS-related DNA repair genes were screened out, after that, a 9-mRNA signature was constructed to measure the risk scores of patients with different outcomes. In addition, a nomogram contained the 9-mRNA model and clinical parameters was also presented to assess the prognosis. Patients with low risk were more likely to have sensitivity to paclitaxel, vinblastine, rapamycin, metformin, imatinib, Akt inhibitor and lapatinib.

Conclusions

The identified highly enriched gene sets may offer a novel insight into the tumorigenesis and treatment of EC. Additionally, the constructed 9-mRNA model and the nomogram have prominent clinical implications for prognosis evaluation and specific therapy guidance for EC patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-020-07712-5.

Gain-of-function hot spot mutant p53R248Q regulation of integrin/FAK/ERK signaling in esophageal squamous cell carcinoma

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Majority of the missense p53 mutants are functionally dispensable in ESCC.

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P53 hot spot mutant p53^R248Q exerts specific gain-of-function oncogenic effects in ESCC.

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Depletion of p53^R248Q suppresses in vitro colony formation and cell cycle progression in a three-dimensional extracellular matrix-rich culture model and in vivo tumor growth.

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P53^R248Q regulates the integrin/FAK/ERK signaling axis.

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P53^R248Q enhances cell proliferation upon glutamine deprivation.

Purpose

TP53, encoding the protein p53, is among the most frequently mutated genes in all cancers. A high frequency of 60 – 90% mutations is seen in esophageal squamous cell carcinoma (ESCC) patients. Certain p53 mutants show gain-of-function (GoF) oncogenic features unrelated to its wild type functions.

Methods

This study functionally characterized a panel of p53 mutants in individual ESCC cell lines and assayed for GoF oncogenic properties.

Results

The ESCC cell line with endogenous p53^R248Q expression showed suppressed tumor growth in an immunocompromised mouse model and suppressed colony growth in in vitro three-dimensional culture, when depleted of the endogenous p53 protein expression. This suppression is accompanied by suppressed cell cycle progression, along with reduced integrin expression and decreased focal adhesion kinase and extracellular-regulated protein kinase signaling and can be compensated by expression of a constitutively active mitogen-activated protein. P53^R248Q enhances cell proliferation upon glutamine deprivation, as compared to other non-GoF mutants.

Conclusions

In summary, study of the functional contributions of endogenous p53 mutants identified a novel GoF mechanism through which a specific p53 mutant exerts oncogenic features and contributes to ESCC tumorigenesis.

PA28γ, an Accomplice to Malignant Cancer

PA28γ is a nuclear activator of the 20S proteasome, which is involved in the regulation of several essential cellular processes and angiogenesis. Over the past 20 years, many amino acid sites and motifs have been proven to play important roles in the characteristic functions of PA28γ. The number of binding partners and validated cellular functions of PA28γ have increased, which has facilitated the clarification of its involvement in different biological events. PA28γ is involved in the progression of various diseases, and its aberrant overexpression in cancer is remarkable. Patients with low levels of PA28γ expression have a higher survival rate than those with high levels of PA28γ expression, as has been shown for a wide variety of tumors. The functions of PA28γ in cancer can be divided into five main categories: cell proliferation, cell apoptosis, metastasis and invasion, cell nuclear dynamics that have relevance to angiogenesis, and viral infection. In this review, we focus on the role of PA28γ in cancer, summarizing its aberrant expression, prooncogenic effects and underlying mechanisms in various cancers, and we highlight the possible cancer-related applications of PA28γ, such as its potential use in the diagnosis, targeted treatment and prognostic assessment of cancer.

Trash Talk: Mammalian Proteasome Regulation at the Transcriptional Level

The key to a healthy mammalian cell lies in properly functioning proteolytic machineries called proteasomes. The proteasomes are multisubunit complexes that catalyze the degradation of unwanted proteins and also control half-lives of key cellular regulatory factors. Aberrant proteasome activity is often associated with human diseases such as cancer and neurodegeneration, and so an in-depth understanding of how it is regulated has implications for potential disease interventions. Transcriptional regulation of the proteasome can dictate its abundance and also influence its function, assembly, and location. This ensures proper proteasomal activity in response to developmental cues and to physiological conditions such as starvation and oxidative stress. In this review, we highlight and discuss the roles of the transcription factors that are involved in the regulation of the mammalian proteasome.

Role of oncogenic REGγ in cancer

Cancer is a critical global health-care problem with limited therapeutic options. Since cancers are life-threatening illnesses, the identification of a promising oncotarget and its clinical correlates are relevant. Mounting evidence has emerged indicating that REG gamma (REGγ), a member of the 11S proteasome activators, plays a pivotal role in the development of multiple human cancers. However, an elaborate summary on the association between REGγ and cancer is still lacking. In this Review, we discuss how REGγ, through its ATP- and ubiquitin-independent manners, represents a promising cancer biomarker and therapeutic oncotarget for multiple human cancers. Aberrant REGγ expression closely associated with tumorigenesis attributes to its biological functions for controlling and regulating cell cycle, proliferation, migration, invasion, angiogenesis, and metastasis of the cancer cells by degrading proteins of cytosol and nucleus in the eukaryotic cells. REGγ serves as a molecular switch to activate multifarious oncogenic signaling pathways, such as MAPK/p38, TGF-β/Smad, and Wnt/β-catenin. The review describes that targeting REGγ may provide new diagnostic and therapeutic applications in cancer.

SPARC-p53: The double agents of cancer

Cancer is a complex disease with high incidence and mortality rates. The important role played by the tumor microenvironment in regulating oncogenesis, tumor growth, and metastasis is by now well accepted in the scientific community. SPARC is known to participate in tumor-stromal interactions and impact cancer growth in ambiguous ways, which either enhance or suppress cancer aggressiveness, in a context-dependent manner. p53 transcription factor, a well-established tumor suppressor, has been reported to promote tumor growth in certain situations, such as hypoxia, thus displaying a duality in its action. Although both proteins are being tested in clinical trials, the synergistic relation between them is yet to be explored in clinical practice. In this review, we address the controversial roles of SPARC and p53 as double agents in cancer, briefly summarizing the interaction found between these two molecules and its importance in cancer.

Double Agent: SPDEF Gene with Both Oncogenic and Tumor-Suppressor Functions in Breast Cancer

The dichotomy of cancer-regulatory genes into “oncogenes (OCGs)” and “tumor-suppressor genes (TSGs)” has greatly helped us in learning molecular details of tumor biology. SPDEF, known as the prostate-derived ETS factor, is reported to play a pivotal role in normal cell development and survival, which has also been endowed with dual characteristics in cancers. Breast cancer (BC) is a highly heterogeneous disease which becomes the leading reason for cancer-related fatality among women worldwide. The involvement of SPDEF in many aspects of BC has been postulated, whereas the mechanism governing the regulation of the pro- and anti-oncogenic activities of SPDEF in BC state remains poorly defined. In this review, we summarized SPDEF as the double agent involving in expression profiles, the regulatory mechanism in BC progression, as well as the role in diagnosis, treatment and prognosis of BC. The understanding of SPDEF duality has contributed to gain insight into the tumor biology and also add a new dimension to the new therapy targets for BC.

REG γ knockdown suppresses proliferation by inducing apoptosis and cell cycle arrest in osteosarcoma

Background

Osteosarcoma (OS) is the most common malignant bone tumor with high mortality in children and adolescents. REG γ is overexpressed and plays oncogenic roles in various types of human cancers. However, the expression and potential roles of REG γ in osteosarcoma are elusive. This study aims at exploring possible biological functions of REG γ in the pathogenesis of osteosarcoma and its underlying mechanism.

Methods

Quantitativereverse transcription-polymerase chain reaction (qRT-PCR), western blotting andimmunohistochemistry (IHC)were performed to detect the expression levels of REG γ in OS tissues and cell lines. Then, the effects of REG γ expression on OS cell proliferation in vitro were analyzed by Cell Counting Kit-8 (CCK-8), ethylene deoxyuridine (EdU), colony formation, flow cytometry. The protein levels of apoptosis and cell-cycle related proteins were evaluated using western blotting.

Results

In present study, we found for the first time that REG γ is overexpressed in osteosarcoma tissues and cell lines and knockdown of REG γ significantly inhibits cell proliferation and induces apoptosis and cell cycle arrest in osteosarcoma cells. Furthermore, we observed that p21, caspase-3 and cleaved caspase-3 are increased while the expression of cycinD1 and bcl-2 are decreased after REG γ depletion in osteosarcoma cells. In conclusion, REG γ may be involved in the proliferation of osteosarcoma and serve as a novel therapeutic target in patients with osteosarcoma.

[Construction of an oral squamous cell carcinoma cell line for stable PA28γ overexpression]

OBJECTIVE

To construct a PA28γ overexpression cell line and determine its effects after infecting an oral squa-mous cell carcinoma (OSCC) cell line.

METHODS

The PA28γ gene was cloned into the pLOV.CMV.cherry.2A.EF1a.PuroR lentiviral vector by polymerase chain reaction (PCR), and PCR and DNA sequencing alignment analysis were used for identification. Then, 293T cells were used to package viral diseases. Infected OSCC cells were used to construct a cell line with stable PA28γ overexpression. Finally, the level of PA28γ expression in the OSCC cell line was detected through Western blot.

RESULTS

The successful construction of PA28γ recombinant lentiviral vectors was confirmed by DNA sequencing. The results of immunofluorescence showed that the PA28γ overexpression lentivirus successfully infected the OSCC cells and showed cherry red fluorescence. The results of Western blot demonstrated that the constructed cells with stable PA28γ overexpression significantly increased the expression of PA28γ.

CONCLUSIONS

The PA28γ overexpression lentiviral vector can significantly increase its protein expression in OSCC cells. We provide a stable OSCC cell line for further study on the effect of PA28γ in OSCC.

Gain-of-Function Mutant p53: All the Roads Lead to Tumorigenesis

The p53 protein is mutated in about 50% of human cancers. Aside from losing the tumor-suppressive functions of the wild-type form, mutant p53 proteins often acquire inherent, novel oncogenic functions, a phenomenon termed mutant p53 gain-of-function (GOF). A growing body of evidence suggests that these pro-oncogenic functions of mutant p53 proteins are mediated by affecting the transcription of various genes, as well as by protein-protein interactions with transcription factors and other effectors. In the current review, we discuss the various GOF effects of mutant p53, and how it may serve as a central node in a network of genes and proteins, which, altogether, promote the tumorigenic process. Finally, we discuss mechanisms by which "Mother Nature" tries to abrogate the pro-oncogenic functions of mutant p53. Thus, we suggest that targeting mutant p53, via its reactivation to the wild-type form, may serve as a promising therapeutic strategy for many cancers that harbor mutant p53. Not only will this strategy abrogate mutant p53 GOF, but it will also restore WT p53 tumor-suppressive functions.

Targeting the Oncogenic p53 Mutants in Colorectal Cancer and Other Solid Tumors

Colorectal cancer (CRC) is a kind of solid tumor and the third most common cancer type in the world. It is a heterogeneous disease characterized by genetic and epigenetic aberrations. The TP53 mutation is the key step driving the transition from adenoma to adenocarcinoma. The functional roles of TP53 mutation in tumor development have been comprehensively investigated. In CRC, TP53 mutation was associated with poor prognosis and chemoresistance. A gain of function (GOF) of p53 mutants promotes cell proliferation, migration and invasion through multiple mechanisms. Restoring wild type p53 function, depleting p53 mutants, or intervention by targeting the oncogenic downstreams provides potential therapeutic strategies. In this review, we comprehensively summarize the GOF of p53 mutants in CRC progression as well as in some other solid tumors, and discuss the current strategies targeting p53 mutants in malignancies.

Silencing PSME3 induces colorectal cancer radiosensitivity by downregulating the expression of cyclin B1 and CKD1

Resistance to radiotherapy remains a severe obstacle in the treatment of high-risk colorectal cancer patients. Recent studies have indicated that proteasome activator complex subunit 3 (PSME3) participates in the development and progression of various human malignancies and is proposed to play a role in tumor radioresistance. However, the impact of PSME3 on radioresistance of colorectal cancer has been largely unknown. In the present study, the enhanced expression of PSME3 was observed in colorectal cancer cells and tissue. Upregulation of PSME3 was significantly implicated in lymph node state, lymphovascular invasion, and Dukes' stage. Furthermore, high PSME3 expression was closely linked to poorer overall and progression-free survival in patients with colorectal cancer. The study further demonstrated that the proliferative, invasive and migratory potential of colorectal cancer cells was effectively inhibited in vitro after silencing PSME3. Our results verified that knockdown of PSME3 probably triggered cell cycle arrest at the G2/M phase by downregulation of cyclinB1 and CDK1, thereby enhancing the radiosensitivity of colorectal cancer cells. These data illustrated that PSME3 is a promising biomarker predictive of colorectal cancer prognosis and silencing of PSME3 may provide with a new approach for sensitizing the radiotherapy in colorectal cancer.

Impact statement

It is reported that colorectal cancer (CRC) is the third most common cancer worldwide and the fourth leading cause of cancer-related death. At present, the main treatment method of colorectal cancer is surgery, supplemented by radiotherapy and chemotherapy. Among them, radiotherapy plays an important role in the treatment of locally advanced colorectal cancer, surgery, and chemotherapy. Our study found that down-regulation of PSME3 may enhance the radiosensitivity of CRC cells by triggering cell cycle arrest, which suggests that silence PSME3 may provide a new method for improving the radiosensitivity of CRC. What’more, our research also demonstrated that PSME3 may promote proliferation, invasive and migratory potential of CRC cells, which implies that PSME3 might be a biomarker of CRC for early diagnosis and treatment.

Proteasomes and Several Aspects of Their Heterogeneity Relevant to Cancer

The life of every organism is dependent on the fine-tuned mechanisms of protein synthesis and breakdown. The degradation of most intracellular proteins is performed by the ubiquitin proteasome system (UPS). Proteasomes are central elements of the UPS and represent large multisubunit protein complexes directly responsible for the protein degradation. Accumulating data indicate that there is an intriguing diversity of cellular proteasomes. Different proteasome forms, containing different subunits and attached regulators have been described. In addition, proteasomes specific for a particular tissue were identified. Cancer cells are highly dependent on the proper functioning of the UPS in general, and proteasomes in particular. At the same time, the information regarding the role of different proteasome forms in cancer is limited. This review describes the functional and structural heterogeneity of proteasomes, their association with cancer as well as several established and novel proteasome-directed therapeutic strategies.

The prognostic value of the proteasome activator subunit gene family in skin cutaneous melanoma

Background: The functional significance of the proteasome activator subunit (PSME) gene family in the pathogenesis of skin cutaneous melanoma (SKCM) remains to be elucidated. Materials and methods: Clinical data for patients with SKCM, including expression levels of PSME genes, were extracted from TCGA. GO term and KEGG pathway enrichment analyses were performed. Correlations between the expression levels of PSME genes in SKCM were evaluated with the Pearson correlation coefficient. Functional and enrichment analyses were conducted using DAVID. Univariate and multivariate survival analyses adjusted by Cox regression were used to construct a prognostic signature. The mechanisms underlying the association between PSME gene expression and overall survival (OS) were explored with gene set enrichment analysis. Joint-effects survival analysis was performed to evaluate the clinical value of the prognostic signature. Results: The median expression levels of PSME1, PSME2 and PSME3 were significantly higher in SKCM than in normal skin. PSME1, PSME2, and PSME3 were significantly enriched in several biological processes and pathways including cell adhesion, adherens junction organization, regulation of autophagy, cellular protein localization, the cell cycle, apoptosis, and the Wnt and NF-κB pathways. High expression levels of PSME1 and PSME2 combined with a low expression level of PSME3 was associated with favorable OS. Conclusion: Knowledge of the expression levels of the PSME gene family could provide a sensitive strategy for predicting prognosis in SKCM.

Lymph node metastasis in oral cancer is strongly associated with chromosomal instability and DNA repair defects

Oral squamous cell carcinoma (OSCC) is highly prevalent in south and southeast Asia. Many (30-50%) OSCC patients develop lymph node metastasis (LNM), which is the most important prognostic factor in OSCC. To identify genomic correlates of LNM, we compared exome sequences and copy number variation data of blood and tumor DNA from highly contrasting subgroups of patients to reduce false inferences-(i) patients with LNM and (ii) patients with late stage disease but without LNM. We found that LNM is associated with (i) specific hotspot somatic mutations in TP53 and CASP8; (ii) rare nonsilent germline mutations in BRCA2 and FAT1; (iii) mutations in mito-G2/M and nonhomologous end joining (NHEJ) pathways; (iv) recurrent deletion of genes for DNA repair by homologous recombination; and (v) chromosomal instability. LN+ patients with NHEJ pathway mutations have longer disease-free survival. Five genomic features have a high predictive value of LNM.

CP‑31398 attenuates endometrial cancer cell invasion, metastasis and resistance to apoptosis by downregulating MDM2 expression

Endometrial cancer (EC) is one of the most common malignancies of the female reproductive system, and metastasis is a major cause of mortality. In this study, we aimed to explore the role of CP-31398 in the migration, invasion and apoptosis of EC cells by its regulation of the expression of the murine double minute 2 (MDM2) gene. For this purpose, EC tissues and adjacent normal tissues were collected, and the positive expression rate of MDM2 in these tissues was assessed. Subsequently, the cellular 50% inhibitory concentration (IC50) of CP-31398 was measured. The EC RL95-2 and KLE cell lines had a higher MDM2 expression and were thus selected for use in subsequent experiments. The EC cells were then treated with CP-31398 (2 µg/ml), and were transfected with siRNA against MDM2 or an MDM2 overexpression plasmid in order to examine the effects of CP-31398 and MDM2 on EC cell activities. The expression of p53, p21, Bad, Bax, B-cell lymphoma-2 (Bcl-2), cytochrome c (Cyt-c), caspase-3, Cox-2, matrix metalloproteinase (MMP)-2 and MMP-9 was measured to further confirm the effects of CP-31398 on cell migration, invasion and apoptosis. Our results indicated that MDM2 was highly expressed in EC tissues. Notably, EC cell viability decreased with the increasing concentrations of CP-31398. The EC cells treated with CP-31398 or siRNA against MDM2 exhibited an increased apoptosis and a suppressed migration and invasion, corresponding to an increased expression of p53, p21, Bad, Bax, Cyt-c and caspase-3, as well as to a decreased expression of Bcl-2, Cox-2, MMP-2 and MMP-9. Moreover, treatment with CP-31398 and siRNA against MDM2 further enhanced these effects. Taken together, the findings of this study indicate that the CP-31398-mediated downregulation of MDM2 may suppress EC progression via its inhibitory role in EC cell migration, invasion and resistance to apoptosis. Therefore, treatment with CP-31398 may prove to be possible therapeutic strategy for EC.

Mutant p53 increases exosome-mediated transfer of miR-21-3p and miR-769-3p to promote pulmonary metastasis

Objective

Tumor metastasis is a complex, multistep process that depends on tumor cells and their communication with the tumor microenvironment. A p53 gain-of-function mutant has been shown to enhance the tumorigenesis, invasion, and metastasis abilities of tumor cells. This study aimed to investigate the roles of p53 R273H mutation in the tumor microenvironment.

Methods

The in vitro and in vivo effects of the p53 R273H mutant on the invasion and metastasis of HCT116 cells were investigated. Exosomes from wild-type and HCT116-TP53(R273H) cells were cocultured with mouse embryonic fibroblasts (MEFs). The roles of differentially expressed exosomal microRNAs identified by microarray analysis were investigated. The functions of the p53 R273H mutant in tumor cells were also investigated via gene expression microarray and quantitative polymerase chain reaction (qPCR) analyses.

Results

Introducing p53 R273H mutant into HCT116 cells significantly potentiated pulmonary metastasis in vivo. In the presence of exosomes derived from HCT116-TP53(R273H) cells, the exosomes were taken up by MEFs and became activated. Microarray analysis showed that the p53 R273H mutation increased the exosomal levels of miR-21-3p and miR-769-3p. Intriguingly, in clinical samples, miR-21-3p and miR-769-3p levels were significantly higher in patients with a p53 mutation than in those without this mutation. Furthermore, both miR-21-3p and miR-769-3p activated fibroblasts and exerted a synergistic effect via their target genes on the transforming growth factor-β (TGF-β)/Smad signaling pathway. The activated fibroblasts excreted cytokine TGF-β and may have reciprocally induced cancer cells to undergo epithelial-mesenchymal transition (EMT). Indeed, HCT116-TP53(R273H) cells showed increased expression of ZEB1 and SNAI2 and decreased transcription of several cell adhesion molecules.

Conclusions

The mutant p53-exosomal miR-21-3p/miR-769-3p-fibroblast-cytokine circuit appears to be responsible for communication between tumor and stromal cells, with exosomal miRNAs acting as a bridge. miR-21-3p and miR-769-3p are potential predictive markers of pulmonary metastasis and candidate targets for therapeutic interventions.

Regulation of Wnt/β-catenin pathway may be related to Regγ in benign epithelial odontogenic lesions

OBJECTIVES

The aim of this study was to analyze and compare the immunoexpressions of Regγ, Wnt-1, and β-catenin in ameloblastomas, adenomatoid odontogenic tumors (AOTs), and odontogenic keratocysts (OKCs).

STUDY DESIGN

Thirty solid ameloblastomas, 20 AOTs, and 30 OKCs were selected for analysis of the immunoexpression of Regγ, Wnt-1, and β-catenin. Each case was semiquantitatively evaluated in the epithelial component and in their different cellular compartments (membrane, cytoplasm, and nucleus).

RESULTS

Ameloblastomas displayed higher cytoplasmic and nuclear Regγ expression compared with AOTs and OKCs, as well as higher membrane and cytoplasmic Wnt-1 expression (P < .05). β-catenin membrane expression was higher in OKCs compared with ameloblastomas and AOTs (P < .05). Nuclear β-catenin expression was higher in ameloblastomas and AOTs than in OKCs (P < .05). Cytoplasmic and nuclear Regγ expression in AOTs were positively correlated with nuclear β-catenin expression (P < .05).

CONCLUSIONS

The marked expressions of Regγ, Wnt-1, and β-catenin suggest the participation of these proteins in the pathogenesis of the studied lesions. The greater expressions of Regγ, Wnt-1, and nuclear β-catenin in ameloblastomas may be related to their more aggressive behavior. Pro-tumor effects of nuclear β-catenin may be counterbalanced by inhibitory pathways in AOTs, justifying their low aggressiveness.

PA28γ acts as a dual regulator of IL-6 and CCL2 and contributes to tumor angiogenesis in oral squamous cell carcinoma

PA28γ promotes tumor development and progression and is suggested to play a role in tumor angiogenesis, but the molecular mechanisms have not been investigated. Here, we found that PA28γ enhanced the ability of OSCC cells to promote the migration, invasion, and tube formation of HUVECs and promoted tumor-induced angiogenesis in xenograft mice models in vivo. Then, a mechanism study revealed that the expression and secretion of IL-6 and CCL2 were dependent on PA28γ expression. Furthermore, blocking IL-6 or CCL2 or the transcription factor NF-κB induced the inhibition of tube formation in HUVECs co-cultured with PA28γ-overexpression OSCC cell supernatants. Moreover, we revealed that p-STAT3 and p-AKT, which are downstream of the IL-6 and CCL2 signaling axis, were downregulated in HUVECs co-cultured with the PA28γ-silenced supernatant and were upregulated with the PA28γ-overexpressing supernatant. In addition, IL-6, CCL2 and PA28γ expressions were correlated in a clinical OSCC cohort. Collectively, our study indicates that PA28γ contributes to tumor angiogenesis by regulating IL-6 and CCL2. PA28γ may be a novel therapeutic target as a dual regulator of IL-6 and CCL2 for treating PA28γ-positive OSCC.

Proteasome dysregulation in human cancer: implications for clinical therapies

Cancer cells show heightened dependency on the proteasome for their survival, growth, and spread. Proteasome dysregulation is therefore commonly selected in favor of the development of many types of cancer. The vast abnormalities in a cancer cell, on top of the complexity of the proteasome itself, have enabled a plethora of mechanisms gearing the proteasome to the oncogenic process. Here, we use selected examples to highlight some general mechanisms underlying proteasome dysregulation in cancer, including copy number variations, transcriptional control, epigenetic regulation, and post-translational modifications. Research in this field has greatly advanced our understanding of proteasome regulation and will shed new light on proteasome-based combination therapies for cancer treatment.

Expression of p53, Bcl-2 and Bax in endometrial carcinoma, endometrial hyperplasia and normal endometrium: a histopathological study

Our objective was to examine the expression rates of p53, Bcl-2 and Bax in endometrial carcinoma, endometrial hyperplasia and normal endometrium. A total of 94 endometrial frozen sections (carcinoma 48, hyperplasia 21, normal tissue 25) were examined immunohistochemically in terms of the expression rates of p53, Bcl-2 and Bax. All of the specimens in the non-malignant groups were positive for Bax, whereas this rate was 85.4% in the group with malignant specimens (p = .03). Conversely, p53 was expressed only in the cancerous group (77.1%, p < .001). The Bcl-2 expression rate was 54.2% in the cancer group, 76.2% in the group with hyperplasia and 60% in the group containing normal tissue (p = .23). Comparing to the non-malignant specimens, the mean Bcl-2/Bax were significantly higher in the malignant group. In conclusion, Bax under-expression, p53 over-expression and a high Bcl-2 to Bax ratio might be associated with endometrial carcinoma. Bcl-2, however, plays no significant role in this regard. Impact statement What is already known on this subject? The p53, Bcl-2 and Bax are the three major genes that regulate apoptosis. Some studies have suggested that these genes may play a role in the pathogenesis of endometrial carcinoma. The available reports, however, are old and inconclusive. What do the results of this study add? Comparing immunohistochemically obtained p53, the Bcl-2 and Bax expression rates between normal endometrial tissue, endometrial specimens with endometrial hyperplasia and specimens with carcinoma showed that Bax under-expression, p53 over-expression and a high Bcl-2 to Bax ratio were associated with malignancy. Using an up-to-date technique to examine the three major regulators of apoptosis at the same time, in a rather large sample size of both normal and abnormal endometrial tissue specimens simultaneously, are the major advantages of the present work. What are the implications of these findings for clinical practice and/or further research? According to our findings, the status of p53, Bcl-2 and Bax expression in the endometrial tissue can be used for risk stratification of endometrial carcinoma for both screening and preventive purposes.

Dual expression of immunoreactive estrogen receptor β and p53 is a potential predictor of regional lymph node metastasis and postoperative recurrence in endometrial endometrioid carcinoma

Although histological grade and muscular invasion are related to the malignant behaviors of endometrial endometrioid carcinoma, lymphatic and/or distant metastases are unexpectedly encountered, even in patients in the low-risk group. To re-evaluate additional reliable parameters to predict the risk of progression, we examined the immunohistochemical expression profiles of p53 and estrogen receptor (ER) β proteins. Patients with endometrial endometrioid carcinoma who underwent surgical treatment at our hospital (n = 154) were recruited to this study, and the significance of the relationships between the incidence of regional lymph node metastasis and/or postoperative recurrence and clinical or experimental parameters was evaluated. By multivariate analysis, we found that histological grades, detection of immunoreactive p53 (positive rates more than 10%, p53-stained), and high expression of ERβ (high-ERβ) were independently associated with metastasis and/or recurrence. Among these parameters, the sensitivity and negative predictive values of high-ERβ were very high (up to 100%). In the population with high-ERβ, the positive rates of metastasis and/or recurrence were 61.1% in the p53-stained group and 21.9% in the p53-non-stained (negative) group. Furthermore, the positive rate in the group showing myometrial invasion of more than 1/2 and showing both p53-stained and high-ERβ was 80%. The disease-free survival of patients who were double-positive for p53-stained and high-ERβ was significantly shorter than that in other patients. In summary, our findings showed that increases in ERβ and p53 immunoreactivity were significantly correlated with the incidence of metastasis and/or recurrence in endometrial endometrioid carcinoma, suggesting that double-positivity for p53-stained and high-ERβ may provide a promising clinical indicator to predict the risk of progression.

Knockdown of REGγ inhibits the proliferation and migration and promotes the apoptosis of multiple myeloma cells by downregulating NF-κB signal pathway

OBJECTIVES

This study aimed to evaluate the effects of REGγ knockdown on the proliferation, apoptosis and migration of multiple myeloma (MM) cells, and reveal the potential regulatory mechanisms.

METHODS

The expression of REGγ on myeloma cells of 28 MM patients was detected by Western blot. shRNA-REGγ-1 and shRNA-REGγ-2 were constructed to downregulate REGγ in RPMI-8226 cells. The proliferation, apoptosis and migration of transfected cells were analyzed by Cell Counting Kit 8 (CCK8), flow cytometry and transwell chamber, respectively. The expression of phosphorylated p65 (p-p65), p65, NF-kappa-B inhibitor ε (IkBε), matrix metalloproteinase 2 (MMP2), B-cell lymphoma xL (Bcl-xL) and X-linked inhibitor of apoptosis protein (XIAP) in transfected cells was detected by Western blot. Using cycloheximide (CHX), the half-life period of IkBε was detected by Western blot.

RESULTS

The expression of REGγ was positive in myeloma cells. The proliferation and migration of RPMI-8226 cells were significantly inhibited by shRNA-REGγ-1/shRNA-REGγ-2, while the apoptosis rates were significantly increased (p < 0.05). The expression of p-p65 and IkBε was significantly reduced in RPMI-8226 cells transfected with shRNA-REGγ-1/shRNA-REGγ-2. The degradation of IkBε was significantly lower in RPMI-8226 cells transfected with shRNA-REGγ-1 than the control (longer half-life period). Besides, the expression of MMP2, Bcl-xL and XIAP in RPMI-8226 cells was significantly inhibited by shRNA-REGγ-1/shRNA-REGγ-2.

DISCUSSION

Knockdown of REGγ may inhibit the proliferation and migration, and promote the apoptosis of RPMI-8226 cells possibly by downregulating NF-κB signal pathway.

Mutant p53 stimulates cell invasion through an interaction with Rad21 in human ovarian cancer cells

Missense mutations of TP53 are extremely common, and mutant p53 accumulation and gain-of-function play crucial roles in human ovarian cancer. Here, we investigated the role of mutant p53 in cell migration and invasion as well as its underlying molecular mechanisms in human ovarian cancer cells. Overexpression of mutant p53 significantly increased migration and invasion in p53-null SKOV3 cells. In contrast, knockdown of mutant p53 significantly compromised mutant p53-induced cell migration and invasion. Microarray analysis revealed that several migration/invasion-related genes, including S1PR1 (Sphingosine-1-phosphate receptor 1) and THBS1 (Thrombospodin 1), were significantly upregulated in SKOV3 cells that overexpressed mutant p53-R248 (SKOV3^R248). We found that Rad21 is involved in the transcriptional regulation of the migration/invasion-related genes induced by mutant p53-R248. Knockdown of Rad21 significantly attenuated the mutant p53-R248-induced invasion and the expressions of S1PR1 and THBS1. Moreover, co-immunoprecipitation and chromatin immunoprecipitation assays revealed that mutant p53 interacts with Rad21 and binds to the Rad21-binding elements in the S1PR1 and THBS1 genes. Finally, downregulation of S1PR1 significantly attenuated the invasion driven by mutant p53-R248. These novel findings reveal that mutant p53-R248 maintains gain-of-function activity to stimulate cell invasion and induces the related gene expressions through an interaction with Rad21 in human ovarian cancer cells.

Epithelial-to-Mesenchymal Transition in the Female Reproductive Tract: From Normal Functioning to Disease Pathology

Epithelial-to-mesenchymal transition (EMT) is a physiological process that is vital throughout the human lifespan. In addition to contributing to the development of various tissues within the growing embryo, EMT is also responsible for wound healing and tissue regeneration later in adulthood. In this review, we highlight the importance of EMT in the development and normal functioning of the female reproductive organs (the ovaries and the uterus) and describe how dysregulation of EMT can lead to pathological conditions, such as endometriosis, adenomyosis, and carcinogenesis. We also summarize the current literature relating to EMT in the context of ovarian and endometrial carcinomas, with a particular focus on how molecular mechanisms and the tumor microenvironment can govern cancer cell plasticity, therapy resistance, and metastasis.

Does rarity mean imparity? Biological characteristics of osteosarcoma cells originating from the spine

PURPOSE

Osteosarcoma is one of the most common malignancies in bones and is often found in limbs. Until now, it is not clear why osteosarcoma is rare in the spine. On the other hand, previous biological characteristics study about osteosarcoma of spine was also rare because of its low incidence. To explore the biology of spinal osteosarcoma, a stable osteosarcoma cell line derived from spine is necessary.

METHODS

A novel osteosarcoma cell line named NEO217 was established from spinal osteosarcoma tissues obtained from a Chinese male patient. We performed a series of experiments to investigate the biological properties of NEO217, including cell morphology, the kinetics of cell growth, biomarkers and tumorigenicity.

RESULTS

The cell line NEO217 was passaged in vitro for more than 50 generations. Ultramicroscopic structural features of these cells were consistent with the pleomorphism characteristic of cancer cells. The average cell doubling time was 26 h. The chromosomal morphology was that of a human karyotype, with the number of chromosomes more than 80. NEO217 cells and available osteosarcoma cell lines such as MG-63 and MNNG/HOS were all CD29⁺CD59⁺ phenotype as detected by flow cytometry. Inoculation of NEO217 cells to immunodeficient mice led to tumor formation. The biological and molecular properties of NEO217 cell line are not exactly the same as some human osteosarcoma cell lines derived from the extremities.

CONCLUSION

We have established a novel osteosarcoma cell line NEO217 derived from the spine, which will provide a useful model for biological or therapeutical studies of spinal osteosarcoma.

Towards standardization of next-generation sequencing of FFPE samples for clinical oncology: intrinsic obstacles and possible solutions

BACKGROUND

Next generation sequencing has a potential to revolutionize the management of cancer patients within the framework of precision oncology. Nevertheless, lack of standardization decelerated entering of the technology into the clinical testing space. Here we dissected a number of common problems of NGS diagnostics in oncology and introduced ways they can be resolved.

METHODS

DNA was extracted from 26 formalin fixed paraffin embedded (FFPE) specimens and processed with the TrueSeq Amplicon Cancer Panel (Illumina Inc, San Diego, California) targeting 48 cancer-related genes and sequenced in single run. Sequencing data were comparatively analyzed by several bioinformatics pipelines.

RESULTS

Libraries yielded sufficient coverage to detect even low prevalent mutations. We found that the number of FFPE sequence artifacts significantly correlates with pre-normalization concentration of libraries (rank correlation -0.81; p < 1e-10), thus, contributing to sample-specific variant detection cut-offs. Surprisingly, extensive validation of EGFR mutation calls by a combination of aligners and variant callers resulted in identification of two false negatives and one false positive that were due to complexity of underlying genomic change, confirmed by Sanger sequencing. Additionally, the study of the non-EGFR amplicons revealed 33 confirmed unique mutations in 17 genes, with TP53 being the most frequently mutated. Clinical relevance of these finding is discussed.

CONCLUSIONS

Reporting of entire mutational spectrum revealed by targeted sequencing is questionable, at least until the clinically-driven guidelines on reporting of somatic mutations are established. The standardization of sequencing protocols, especially their data analysis components, requires assay-, disease-, and, in many cases, even sample-specific customization that could be performed only in cooperation with clinicians.

Novel targets and interaction partners of mutant p53 Gain-Of-Function

In many human cancers p53 expression is lost or a mutant p53 protein is expressed. Over the past 15 years it has become apparent that a large number of these mutant p53 proteins have lost wild type function, but more importantly have gained functions that promote tumorigenesis and drive chemo-resistance, invasion and metastasis. Many researchers have investigated the underlying mechanisms of these Gain-Of-Functions (GOFs) and it has become apparent that many of these functions are the result of mutant p53 hijacking other transcription factors. In this review, we summarize the latest research on p53 GOF and categorize these in light of the hallmarks of cancer as presented by Hannahan and Weinberg.

Proteasome activator subunit 3 promotes pancreatic cancer growth via c-Myc-glycolysis signaling axis

Pancreatic cancer has the worst prognosis among all cancers and novel markers and therapeutic targets are desperately needed for this terribly deadly disease. Proteasome activator subunit 3 (PSME3) is highly involved in the initiation and progression of many human cancers. However, the potential effect of PSME3 on pancreatic cancer remains largely unknown. In the present study, we first found that PSME3 was significantly upregulated in pancreatic cancer cells and tissues at both mRNA and protein levels using qRT-PCR, western blot analysis, Oncomine data mining and immunohistochemical analysis. High PSME3 expression was positively correlated with tumor size and pM stage, and was significantly correlated with poor prognosis in pancreatic cancer patients revealed by Kaplan-Meier analysis. Gene set enrichment analysis demonstrated that the gene sets related to cell proliferation and metastasis were positively correlated with elevated PSME3 expression. Consistently, silencing of PSME3 suppressed cell proliferation and invasive capacity of pancreatic cancer. Mechanistically, PSME3 inhibited the degradation of c-Myc and thus enhanced glycolysis, which ultimately led to the oncogenic effects of PSME3 on pancreatic cancer. Collectively, our data suggest that PSME3 plays oncogenic roles in pancreatic cancer by inhibiting c-Myc degradation to promote glycolysis, and could serve as a novel therapeutic target for pancreatic cancer treatment.

Oncogenic Mutant p53 Gain of Function Nourishes the Vicious Cycle of Tumor Development and Cancer Stem-Cell Formation

More than half of human tumors harbor an inactivated p53 tumor-suppressor gene. It is well accepted that mutant p53 shows an oncogenic gain-of-function (GOF) activity that facilitates the transformed phenotype of cancer cells. In addition, a growing body of evidence supports the notion that cancer stem cells comprise a seminal constituent in the initiation and progression of cancer development. Here, we elaborate on the mutant p53 oncogenic GOF leading toward the acquisition of a transformed phenotype, as well as placing mutant p53 as a major component in the establishment of cancer stem cell entity. Therefore, therapy targeted toward cancer stem cells harboring mutant p53 is expected to pave the way to eradicate tumor growth and recurrence.

Expression of mutant p53 in oral squamous cell carcinoma is correlated with the effectiveness of intra-arterial chemotherapy

The aim of the present study was to evaluate the correlation between the positive expression rate of mutant p53 and the clinical characteristics of patients with oral squamous cell carcinoma (OSCC), as well as the effectiveness of intra-arterial chemotherapy. Expression of mutant p53 in tumor tissues was determined by immunohistochemical analysis of 51 OSCC patients, prior to and following intra-arterial chemotherapy. Prior to intra-arterial chemotherapy, mutant p53 positive rates in patients with higher pathological grades were significantly higher than those of the patients with lower pathological grades. The mutant p53 positive rate in patients with lymph node metastasis was 73% (19/26), which was significantly higher than that of the patients without lymph node metastasis (20%, 5/25). Mutant p53 was expressed in 17% (3/18) of clinical phase II patients, while 64% (21/33) of clinical phase III and IV patients exhibited positive expression of mutant p53 (P<0.05). The mutant p53 positive rate in chemotherapy non-responsive patients was 69% (11/16), which was significantly higher than that in the chemotherapy-responsive patients (37%, 13/35). Mutant p53 positive rates were not significantly correlated with age, gender or the location of the tumor. The mutant p53 positive rate prior to chemotherapy was 47% (24/51), and decreased to 18% (9/51) following chemotherapy. Expression of mutant p53 was decreased in all 13 (100%) chemotherapy-responsive patients, while only 5 (45%) chemotherapy non-responsive patients exhibited reduced expression levels of mutant p53 (P<0.05). In conclusion, mutant p53 has a significant role in the differentiation, development and treatment guidance of OSCC. Intra-arterial chemotherapy with 5-fluorourcil and carboplatin potentially exerts a therapeutic effect by reducing the expression of mutant p53.

Associations between proteasomal activator PA28γ and outcome of oral squamous cell carcinoma: Evidence from cohort studies and functional analyses

BACKGROUND

PA28γ was suggested to play a role in malignant progression. This paper aimed to investigate the association between PA28γ and the prognosis of oral squamous cell carcinoma (OSCC) in cohort studies.

METHODS

The PA28γ expression level was assessed by immunohistochemistry in a total of 368 OSCC patients from three independent cohorts. The Cox proportional hazards regression model was used to determine multivariate hazard ratios for Overall Survival (OS). Model discrimination was measured using C Statistic. Additionally, OS was analyzed in Head Neck Squamous Cell Carcinoma (HNSCC) patients from The Cancer Genome Atlas (TCGA) data set. Functional analyses were conducted both in-vitro and in-vivo.

FINDINGS

The median follow-up times of patients in the three studies were 60, 52, and 51 months. High expression of PA28γ was identified in tumors from 179 of 368 patients (48.6%). Compared with low expression, high expression of PA28γ was strongly associated with worse OS, with relative risks of 5.14 (95% CI, 2.51-10.5; P < 0.001), 2.82 (95% CI, 1.73-4.61; P < 0.001), and 3.85 (95% CI, 1.59-9.37; P = 0.003). PA28γ expression was also associated with disease-free survival in all three cohorts (P < 0.005). These findings are consistent with TCGA HNSCC data (P < 0.006). The prediction of all-cause mortality was significantly improved when PA28γ was added to the traditional clinical factors (Model 3, C statistic value: 0.78 VS 0.73, P = 0.016). In functional analyses, we found that PA28γ silencing dramatically inhibited the growth, proliferation and mobility of OSCC cells in vitro and reduced tumor growth and angiogenesis in tumor-bearing mice.

INTERPRETATION

PA28γ overexpression is associated with adverse prognosis in patients with OSCC. The aberrant expression of PA28γ may contribute to the pathogenesis and progression of OSCC.

RESEARCH IN CONTEXT

OSCC is one of the most common HNSCC, which have a high lethally rate. However, few prognostic markers have been applied in the clinical practice. We found that PA28γ in OSCC tumor tissues were significantly high expression than those in normal tissues. As the results of the three cohorts from two independent research centers and from an additional validation cohort from a US population in the TCGA dataset, we demonstrate PA28γ is a good predictor of the risk of death in OSCC. Meanwhile, we demonstrate PA28γ have a potential role in OSCC tumorigenesis.