Inefficient differentiation response to cell cycle stress leads to genomic instability and malignant progression of squamous carcinoma cells

Sumo-regulatory SENP2 controls the homeostatic squamous mitosis-differentiation checkpoint

Squamous or epidermoid cancer arises in stratified epithelia but also is frequent in the non-epidermoid epithelium of the lung by unclear mechanisms. A poorly studied mitotic checkpoint drives epithelial cells bearing irreparable genetic damage into epidermoid differentiation. We performed an RNA-sequencing gene search to target unknown regulators of this response and selected the SUMO regulatory protein SENP2. Alterations of SENP2 expression have been associated with some types of cancer. We found the protein to be strongly localised to mitotic spindles of freshly isolated human epidermal cells. Primary cells rapidly differentiated after silencing SENP2 with specific shRNAs. Loss of SENP2 produced in synchronised epithelial cells delays in mitotic entry and exit and defects in chromosomal alignment. The results altogether strongly argue for an essential role of SENP2 in the mitotic spindle and hence in controlling differentiation. In addition, the expression of SENP2 displayed an inverse correlation with the immuno-checkpoint biomarker PD-L1 in a pilot collection of aggressive lung carcinomas. Consistently, metastatic head and neck cancer cells that do not respond to the mitosis-differentiation checkpoint were resistant to depletion of SENP2. Our results identify SENP2 as a novel regulator of the epithelial mitosis-differentiation checkpoint and a potential biomarker in epithelial cancer.

DNA damage signalling histone H2AX is required for tumour growth

Cancer most frequently develops in self-renewal tissues that are the target of genetic alterations due to mutagens or intrinsic DNA replication errors. Histone γH2AX has a critical role in the cellular DNA repair pathway cascade and contributes to genomic stability. However, the role of γH2AX in the ontology of cancer is unclear. We have investigated this issue in the epidermis, a self-renewal epithelium continuously exposed to genetic hazard and replication stress. Silencing H2AX caused cell cycle hyperactivation, impaired DNA repair and epidermal hyperplasia in the skin. However, mutagen-induced carcinogenesis was strikingly reduced in the absence of H2AX. KO tumours appeared significantly later than controls and were fewer, smaller and more benign. The stem cell marker Δp63 drastically diminished in the KO epidermis. We conclude that H2AX is required for tissue-making during both homoeostasis and tumourigenesis, possibly by contributing to the control and repair of stem cells. Therefore, although H2AX is thought to act as a tumour suppressor and our results show that it contributes to homeostasis, they also indicate that it is required for the development of cancer.

TEX10 Promotes the Tumorigenesis and Radiotherapy Resistance of Urinary Bladder Carcinoma by Stabilizing XRCC6

Urinary bladder carcinoma refers to the commonest carcinoma with weak prognostic result for the patient as impacted by the limited treatment possibilities and challenging diagnosing process. Nevertheless, the molecular underpinning of bladder carcinoma malignant progression is still not clear. As a novel core part of pluripotency circuitry, testicular expression 10 (TEX10) plays an actively noticeable effect on reprogramming, early embryo development, and embryonic stem cell self-renewal. Nevertheless, TEX10 expressions and functions within bladder carcinoma are still not known. The present work is aimed at revealing TEX10 expression and biological function within urinary bladder carcinoma and elucidating the potential mechanisms. Results showed that TEX10 is abundant in urinary bladder carcinoma, and its protein level was related to poor disease-free survival in a positive manner. Reduced TEX10 level inhibited urinary bladder carcinoma cell proliferating process and metastasis in vitro and xenograft tumorigenicity in vivo. Notably, TEX10 might regulate carcinoma cell proliferating process and metastasis via XRCC6, thereby controlling the signaling of Wnt/β-catenin and DNA repair channel. Moreover, TEX10 gene knockout reduced the radiotherapy resistance of urinary bladder carcinoma. In brief, this work revealed that TEX10 could exert a significant carcinogenic effect on urinary bladder carcinoma tumorigenesis and radiotherapy resistance through the activation of XRCC6-related channels. Accordingly, targeting TEX10 is likely to offer a novel and feasible therapeutically related strategy for inhibiting urinary bladder carcinoma tumorigenicity.

Metabolomic Analysis of Actinic Keratosis and SCC Suggests a Grade-Independent Model of Squamous Cancerization

Simple Summary

Actinic keratoses (AKs) are the most common sun-induced precancerous lesions that can progress to squamocellular carcinoma (SCC). AK I have been considered low-risk lesions, often evolving into AK II, the AK grade II and III have the potential to evolve to SCC. This research has assessed the metabolomic fingerprints of AK I, AK II, AK III and SCC by HR-MAS NMR spectroscopy, with the aim of evaluating the hypothesis of grade-association AK to SCC. The association between AKs and SCCs has also been evaluated by histopathology. Our findings support the notion that AK I are different from healthy skin and share different features with SCCs, indeed, they are metabolically active lesions with metabolic profiles similar to high-grade AKs and to SCC. The negative association of AKs with parakeratosis and the positive association with hypertrophy also suggested a similar behavior between AKs and SCCs. Therefore, all AKs should be treated independently from their clinical appearance or histological grade, since it is not possible to predict their potential evolution to SCC.

Abstract

Background—Actinic keratoses (AKs) are the most common sun-induced precancerous lesions that can progress to squamocellular carcinoma (SCC). Recently, the grade-independent association between AKs and SCC has been suggested; however, the molecular bases of this potential association have not been investigated. This study has assessed the metabolomic fingerprint of AK I, AK II, AK III and SCC using high resolution magic angle spinning (HR-MAS) nuclear magnetic resonance (NMR) spectroscopy in order to evaluate the hypothesis of grade-independent association between AK and SCC. Association between AKs and SCCs has also been evaluated by histopathology. Methods—Metabolomic data were obtained through HR-MAS NMR spectroscopy. The whole spectral profiles were analyzed through multivariate statistical analysis using MetaboAnalyst 5.0. Histologic examination was performed on sections stained with hematoxylin and eosin; statistical analysis was performed using STATA software version 14. Results—A group of 35 patients affected by AKs and/or SCCs and 10 healthy controls were enrolled for metabolomics analysis. Histopathological analysis was conducted on 170 specimens of SCCs and AKs (including the ones that underwent metabolomic analysis). SCCs and AK I were found to be significantly associated in terms of the content of some metabolites. Moreover, in the logistic regression model, the presence of parakeratosis in AKs appeared to be less frequently associated with SCCs, while AKs with hypertrophy had a two-fold higher risk of being associated with SCC. Conclusions—Our findings, derived from metabolomics and histopathological data, support the notion that AK I are different from healthy skin and share some different features with SCCs. This may further support the expanding notion that all AKs should be treated independently from their clinical appearance or histological grade because they may be associated with SCC.

Distinct p63 and p73 Protein Interactions Predict Specific Functions in mRNA Splicing and Polyploidy Control in Epithelia

Epithelial organs are the first barrier against microorganisms and genotoxic stress, in which the p53 family members p63 and p73 have both overlapping and distinct functions. Intriguingly, p73 displays a very specific localization to basal epithelial cells in human tissues, while p63 is expressed in both basal and differentiated cells. Here, we analyse systematically the literature describing p63 and p73 protein-protein interactions to reveal distinct functions underlying the aforementioned distribution. We have found that p73 and p63 cooperate in the genome stability surveillance in proliferating cells; p73 specific interactors contribute to the transcriptional repression, anaphase promoting complex and spindle assembly checkpoint, whereas p63 specific interactors play roles in the regulation of mRNA processing and splicing in both proliferating and differentiated cells. Our analysis reveals the diversification of the RNA and DNA specific functions within the p53 family.

The DNA damage response links human squamous proliferation with differentiation

How rapid cell multiplication leads to cell differentiation in developing tissues is still enigmatic. This question is central to morphogenesis, cell number control, and homeostasis. Self-renewal epidermoid epithelia are continuously exposed to mutagens and are the most common target of cancer. Unknown mechanisms commit rapidly proliferating cells to post-mitotic terminal differentiation. We have over-activated or inhibited the endogenous DNA damage response (DDR) pathways by combinations of activating TopBP1 protein, specific shRNAs, or chemical inhibitors for ATR, ATM, and/or DNA-PK. The results dissect and demonstrate that these signals control keratinocyte differentiation in proliferating cells independently of actual DNA damage. The DDR limits keratinocyte multiplication upon hyperproliferative stimuli. Moreover, knocking down H2AX, a common target of the DDR pathways, inhibits the epidermoid phenotype. The results altogether show that the DDR is required to maintain the balance proliferation differentiation and suggest that is part of the squamous program. We propose a homeostatic model where genetic damage is automatically and continuously cleansed by cell-autonomous mechanisms.

p21CIP1 controls the squamous differentiation response to replication stress

The control of cell fate is critical to homeostasis and cancer. Cell cycle cdk inhibitor p21CIP1 has a central and paradoxical role in the regulatory crossroads leading to senescence, apoptosis, or differentiation. p21 is an essential target of tumor suppressor p53, but it also is regulated independently. In squamous self-renewal epithelia continuously exposed to mutagenesis, p21 controls cell fate by mechanisms still intriguing. We previously identified a novel epidermoid DNA damage-differentiation response. We here show that p21 intervenes in the mitosis block that is required for the squamous differentiation response to cell cycle deregulation and replication stress. The inactivation of endogenous p21 in human primary keratinocytes alleviated the differentiation response to oncogenic loss of p53 or overexpression of the DNA replication major regulator Cyclin E. The bypass of p21-induced mitotic block involving upregulation of Cyclin B allowed DNA damaged cells to escape differentiation and continue to proliferate. In addition, loss of p21 drove keratinocytes from differentiation to apoptosis upon moderate UV irradiation. The results show that p21 is required to drive keratinocytes towards differentiation in response to genomic stress and shed light into its dual and paradoxical role in carcinogenesis.

β-HPV 8E6 combined with TERT expression promotes long-term proliferation and genome instability after cytokinesis failure

Human papillomavirus (HPV) is a family of viruses divided into five genera: alpha, beta, gamma, mu, and nu. There is an ongoing discussion about whether beta genus HPVs (β-HPVs) contribute to cutaneous squamous cell carcinoma (cSCC). The data presented here add to this conversation by determining how a β-HPV E6 protein (β-HPV 8E6) alters the cellular response to cytokinesis failure. Specifically, cells were observed after cytokinesis failure was induced by dihydrocytochalasin B (H2CB). β-HPV 8E6 attenuated the immediate toxicity associated with H2CB but did not promote long-term proliferation after H2CB. Immortalization by telomerase reverse transcriptase (TERT) activation also rarely allowed cells to sustain proliferation after H2CB exposure. In contrast, TERT expression combined with β-HPV 8E6 expression allowed cells to proliferate for months following cytokinesis failure. However, this continued proliferation comes with genome destabilizing consequences. Cells that survived H2CB-induced cytokinesis failure suffered from changes in ploidy.

Response of head and neck epithelial cells to a DNA damage-differentiation checkpoint involving polyploidization

BACKGROUND

Squamous epithelia of the head and neck undergo continuous cell renewal and are continuously exposed to mutagenic hazard, the main cause of cancer. How they maintain homeostasis upon cell cycle deregulation is unclear.

METHODS

To elucidate how head and neck epithelia respond to cell cycle stress, we studied human keratinocytes from various locations (oral mucosa, tonsil, pharynx, larynx, and trachea). We made use of genotoxic or mitotic drugs (doxorubicin [DOXO], paclitaxel, and nocodazole), or chemical inhibitors of the mitotic checkpoint kinases, Aurora B and polo-like-1. We further tested the response to inactivation of p53, ectopic cyclin E, or to the chemical carcinogen 7,12-dimethylbenz[a]anthracene (DMBA).

RESULTS

All treatments provoked DNA damage or mitosis impairment and strikingly triggered squamous differentiation and polyploidization, resulting in irreversible loss of clonogenic capacity.

CONCLUSION

Keratinocytes from head and neck epithelia share a cell-autonomous squamous DNA damage-differentiation response that is common to the epidermis and might continuously protect them from cancer.

Tex10 is upregulated and promotes cancer stem cell properties and chemoresistance in hepatocellular carcinoma

Testis expressed 10 (Tex10), a new core component of the pluripotency circuitry, has been reported to positively regulate embryonic stem cell (ESC) super-enhancers to promote ESC self-renewal; however, the expression and function of Tex10 in hepatocellular carcinoma (HCC) and liver cancer stem cells remains unclear. The present study was designed to investigate the expression patterns of Tex10 with immunohistochemistry, western blotting and RT-qPCR in samples from HCC patients and HCC cell lines. The results obtained show that Tex10 was highly expressed in HCC tissues, and elevated Tex10 protein levels positively correlate with the poorly differentiated carcinoma. Likewise, we found that Tex10 expression in the high-metastasis HCCLM3 potential cell line was higher than that in the low-metastasis HepG2 potential cell line, and Tex10 expression in liver cancer stem cells was also higher than that in adhered HCC cells. In addition, Tex10 knockdown decreased stem cell marker expression and drug resistance. Tex10 promoted cancer stemness through activation of the STAT3 signaling pathway. Taken together, our study demonstrates that Tex10 plays a potent carcinogenic role in HCC tumorigenesis by maintaining cancer stem cell properties through activation of the STAT3 signaling pathway and promoting chemo-resistance. Thus, targeting Tex10 may provide a novel and effective therapeutic strategy to suppress the tumorigenicity of advanced HCC.

Mammalian endoreplication emerges to reveal a potential developmental timer

Among the most intriguing and relevant questions in physiology is how developing tissues correctly coordinate proliferation with differentiation. Endoreplication, in a broad sense, is a consequence of a cell division block in the presence of an active cell cycle, and it typically occurs as cells differentiate terminally to fulfill a specialised function. Until recently, endoreplication was thought to be a rare variation of the cell cycle in mammals, more common in invertebrates and plants. However, in the last years, endoreplication has been uncovered in various tissues in mammalian organisms, including human. A recent report showing that cells in the mammary gland become binucleate at lactation sheds new insight into the importance of mammalian polyploidisation. We here propose that endoreplication is a widespread phenomenon in mammalian developing tissues that results from an automatic, robust and simple self-limiting mechanism coordinating cell multiplication with differentiation. This mechanism might act as a developmental timer. The model has implications for homeostasis control and carcinogenesis.