Mutation and homozygous deletion analyses of genes that control the G1/S transition of the cell cycle in skin melanoma: p53, p21, p16 and p15

Senescent tumor cells in colorectal cancer are characterized by elevated enzymatic activity of complexes 1 and 2 in oxidative phosphorylation

BACKGROUND

Cellular senescence is defined as an irreversible cell cycle arrest caused by various internal and external insults. While the metabolic dysfunction of senescent cells in normal tissue is relatively well-established, there is a lack of information regarding the metabolic features of senescent tumor cells.

METHODS

Publicly available single-cell RNA-sequencing data from the GSE166555 and GSE178341 datasets were utilized to investigate the metabolic features of senescent tumor cells. To validate the single-cell RNA-sequencing data, we performed senescence-associated β-galactosidase (SA-β-Gal) staining to identify senescent tumor cells in fresh frozen colorectal cancer tissue. We also evaluated nicotinamide adenine dinucleotide dehydrogenase-tetrazolium reductase (NADH-TR) and succinate dehydrogenase (SDH) activity using enzyme histochemical methods and compared the staining with SA-β-Gal staining. MTT assay was performed to reveal the complex 1 activity of the respiratory chain in in-vitro senescence model.

RESULTS

Single-cell RNA-sequencing data revealed an upregulation in the activity of complexes 1 and 2 in oxidative phosphorylation, despite overall mitochondrial dysfunction in senescent tumor cells. Both SA-β-Gal and enzyme histochemical staining using fresh frozen colorectal cancer tissues indicated a high correlation between SA-β-Gal positivity and NADH-TR/SDH staining positivity. MTT assay showed that senescent colorectal cancer cells exhibit higher absorbance in 600 nm wavelength.

CONCLUSIONS

Senescent tumor cells exhibit distinct metabolic features, characterized by upregulation of complexes 1 and 2 in the oxidative phosphorylation pathway. NADH-TR and SDH staining represent efficient methods for detecting senescent tumor cells in colorectal cancer.

Reciprocal Regulation between lncRNA ANRIL and p15 in Steroid-Induced Glaucoma

Steroid-induced glaucoma (SIG) is the most common adverse steroid-related effect on the eyes. SIG patients can suffer from trabecular meshwork (TM) dysfunction, intraocular pressure (IOP) elevation, and irreversible vision loss. Previous studies have mainly focused on the role of extracellular matrix turnover in TM dysfunction; however, whether the cellular effects of TM cells are involved in the pathogenesis of SIG remains unclear. Here, we found that the induction of cellular senescence was associated with TM dysfunction, causing SIG in cultured cells and mouse models. Especially, we established the transcriptome landscape in the TM tissue of SIG mice via microarray screening and identified ANRIL as the most differentially expressed long non-coding RNA, with a 5.4-fold change. The expression level of ANRIL was closely related to ocular manifestations (IOP elevation, cup/disc ratio, and retinal nerve fiber layer thickness). Furthermore, p15, the molecular target of ANRIL, was significantly upregulated in SIG and was correlated with ocular manifestations in an opposite direction to ANRIL. The reciprocal regulation between ANRIL and p15 was validated using luciferase reporter assay. Through depletion in cultured cells and a mouse model, ANRIL/p15 signaling was confirmed in cellular senescence via cyclin-dependent kinase activity and, subsequently, by phosphorylation of the retinoblastoma protein. ANRIL depletion imitated the SIG phenotype, most importantly IOP elevation. ANRIL depletion-induced IOP elevation in mice can be effectively suppressed by p15 depletion. Analyses of the single-cell atlas and transcriptome dynamics of human TM tissue showed that ANRIL/p15 expression is spatially enriched in human TM cells and is correlated with TM dysfunction. Moreover, ANRIL is colocalized with a GWAS risk variant (rs944800) of glaucoma, suggesting its potential role underlying genetic susceptibility of glaucoma. Together, our findings suggested that steroid treatment promoted cellular senescence, which caused TM dysfunction, IOP elevation, and irreversible vision loss. Molecular therapy targeting the ANRIL/p15 signal exerted a protective effect against steroid treatment and shed new light on glaucoma management.

Cellular Senescence in the Treatment of Ovarian Cancer

Objective

This review aimed to update the research and development of cellular senescence in the treatment of ovarian cancer. We discussed the current mechanisms of senescence and the major biomarkers of senescence, especially the methods of cellular senescence in the treatment of ovarian cancer.

Materials and Methods

We collected all relevant studies in PubMed from 1995 to 2017. The search terms included senescence and cancer, senescence and ovarian cancer, senescence-associated secretory phenotype, ovarian cancer and chemotherapy, radiotherapy, or biotherapy. PubMed search with the key words senescence and ovarian cancer lists approximately 85 publications. After excluding the duplicated articles, we selected 68 articles most relevant to senescence and ovarian cancer in this review.

Results

Cellular senescence plays a key role in various biological processes of ovarian cancer, which is closely related with the occurrence, development, and treatment of ovarian cancer. Cellular senescence on the one hand can reduce the dose of chemotherapy in ovarian cancer; on the other hand, it also can solve the problem of tumor resistance to apoptosis. Therefore, cellular senescence has been shown to be the third intracellular mechanism of ovarian cancer prevention followed by cellular DNA repair and apoptosis.

Conclusions

In the near future, cellular senescence therapy could be a powerful tool for ovarian cancer treatment.

Identification of Cyclobutane Pyrimidine Dimer-Responsive Genes Using UVB-Irradiated Human Keratinocytes Transfected with In Vitro-Synthesized Photolyase mRNA

Major biological effects of UVB are attributed to cyclobutane pyrimidine dimers (CPDs), the most common photolesions formed on DNA. To investigate the contribution of CPDs to UVB-induced changes of gene expression, a model system was established by transfecting keratinocytes with pseudouridine-modified mRNA (Ψ-mRNA) encoding CPD-photolyase. Microarray analyses of this model system demonstrated that more than 50% of the gene expression altered by UVB was mediated by CPD photolesions. Functional classification of the gene targets revealed strong effects of CPDs on the regulation of the cell cycle and transcriptional machineries. To confirm the microarray data, cell cycle-regulatory genes, CCNE1 and CDKN2B that were induced exclusively by CPDs were selected for further investigation. Following UVB irradiation, expression of these genes increased significantly at both mRNA and protein levels, but not in cells transfected with CPD-photolyase Ψ-mRNA and exposed to photoreactivating light. Treatment of cells with inhibitors of c-Jun N-terminal kinase (JNK) blocked the UVB-dependent upregulation of both genes suggesting a role for JNK in relaying the signal of UVB-induced CPDs into transcriptional responses. Thus, photolyase mRNA-based experimental platform demonstrates CPD-dependent and -independent events of UVB-induced cellular responses, and, as such, has the potential to identify novel molecular targets for treatment of UVB-mediated skin diseases.

Exome sequencing of hepatoblastoma reveals novel mutations and cancer genes in the Wnt pathway and ubiquitin ligase complex

Hepatoblastoma (HB) is the most common primary liver tumor in children. Mutations in the β-catenin gene that lead to constitutive activation of the Wnt pathway have been detected in a large proportion of HB tumors. To identify novel mutations in HB, we performed whole-exome sequencing of six paired HB tumors and their corresponding lymphocytes. This identified 24 somatic nonsynonymous mutations in 21 genes, many of which were novel, including three novel mutations targeting the CTNNB1 (G512V) and CAPRIN2 (R968H/S969C) genes in the Wnt pathway, and genes previously shown to be involved in the ubiquitin ligase complex (SPOP, KLHL22, TRPC4AP, and RNF169). Functionally, both the CTNNB1 (G512V) and CAPRIN2 (R968H/S969C) were observed to be gain-of-functional mutations, and the CAPRIN2 (R968H/S969C) was also shown to activate the Wnt pathway in HB cells. These findings suggested the activation of the Wnt pathway in HB, which was confirmed by immunohistochemical staining of the β-catenin in 42 HB tumors. We further used short hairpin RNA (shRNA)-mediated interference to assess the effect of 21 mutated genes on HB cell survival. The results suggested that one novel oncogene (CAPRIN2) and three tumor suppressors (SPOP, OR5I1, and CDC20B) influence HB cell growth. Moreover, we found that SPOP S119N is a loss-of-function mutation in HB cells. We finally demonstrated that one of the mechanisms by which SPOP inhibits HB cell proliferation is through regulating CDKN2B expression.

CONCLUSION

These results extend the landscape of genetic alterations in HB and highlight the dysregulation of Wnt and ubiquitin pathways in HB tumorigenesis.

Role of PI3K-AKT-mTOR and Wnt Signaling Pathways in Transition of G1-S Phase of Cell Cycle in Cancer Cells

The PI3K-Akt pathway together with one of its downstream targets, the mechanistic target of rapamycin (mTOR; also known as the mammalian target of rapamycin) is a highly deregulated pathway in cancers. mTOR exists in two complexes, mTORC1 and mTORC2. Akt phosphorylated at T308 inhibits TSC1/2 complex to activate mTORC1; mTORC2 is recognized as the kinase phosphorylating Akt at S473. Inhibition of autophagy by mTORC1 was shown to rescue disheveled (Dvl) leading to activation of Wnt pathway. Cyclin D1 and the c-Myc are activated by the Wnt signaling. Cyclin D1 is a key player in initiation of cell cycle. c-Myc triggers metabolic reprograming in G1 phase of cell cycle, which also activates the transcription factors like FoxO and p53 that play key roles in promoting the progression of cell cycle. While the role of p53 in cancer cell metabolism in arresting glycolysis and inhibition of pentose phosphate pathway has come to be recognized, there are confusions in the literature on the role of FoxO and that of rictor. FoxO was shown to be the transcription factor of rictor, in addition to the cell cycle inhibitors like p21. Rictor has dual roles; inhibition of c-Myc and constitution of mTORC2, both of which are key factors in the exit of G1-S phase and entry into G2 phase of cell cycle. A model is presented in this article, which suggests that the PI3K-Akt-mTOR and Wnt pathways converge and regulate the progression of cell cycle through G0-G1-S-phases and reprogram the metabolism in cancer cells. This model is different from the conventional method of looking at individual pathways triggering the cell cycle.

Reviewing the somatic genetics of melanoma: from current to future analytical approaches

Metastatic melanoma has traditionally been difficult to treat, and although molecularly based targeted therapies have shown promising results, they have yet to show consistent improvements in overall survival rates. Thus, identifying the key mutation events underlying the etiology of metastatic melanoma will no doubt lead to the improvement of existing therapeutic approaches and the development of new treatment strategies. Significant advances toward understanding the complexity of the melanoma genome have recently been achieved using next-generation sequencing (NGS) technologies. However, identifying those mutations driving tumorigenesis will continue to be a challenge for researchers, in part because of the high rates of mutation compared to other cancers. This article will review the catalog of mutations identified in melanoma through a variety of approaches, including the use of unbiased exome and whole-genome NGS platforms, as well discuss complementary strategies for identifying driver mutations. The promise of personalized medicine afforded by better understanding these mutation events should provide impetus for increased activity and rapid advances in this field.

Targeted disruption of Nemo-like kinase inhibits tumor cell growth by simultaneous suppression of cyclin D1 and CDK2 in human hepatocellular carcinoma

The Wnt/beta-catenin signaling pathway regulates various aspects of development and plays important role in human carcinogenesis. Nemo-like kinase (NLK), which is mediator of Wnt/beta-catenin signaling pathway, phosphorylates T-cell factor/lymphoid enhancer factor (TCF/LEF) factor and inhibits interaction of beta-catenin/TCF complex. Although, NLK is known to be a tumor suppressor in Wnt/beta-catenin signaling pathway of colon cancer, the other events occurring downstream of NLK pathways in other types of cancer remain unclear. In the present study, we identified that expression of NLK was significantly up-regulated in the HCCs compared to corresponding normal tissues in five selected tissue samples. Immunohistochemical analysis showed significant over-expression of NLK in the HCCs. Targeted-disruption of NLK suppressed cell growth and arrested cell cycle transition. Suppression of NLK elicited anti-mitogenic properties of the Hep3B cells by simultaneous inhibition of cyclinD1 and CDK2. The results of this study suggest that NLK is aberrantly regulated in HCC, which might contribute to the mitogenic potential of tumor cells during the initiation and progression of hepatocellular carcinoma; this process appears to involve the induction of CDK2 and cyclin D1 and might provide a novel target for therapeutic intervention in patients with liver cancer.

Mutations in Exons 6 and 7 of TP53 Gene Correlate Positively with Serum Tumor Necrosis Factor Alpha Independent of Microsatellite Instability in BAT26 Gene in Egyptian Patients with Endometrial Carcinoma

Abnormalities in the TP53 gene are the most frequent genetic alterations in human cancers. The role and mechanism of TP53 mutations have been well studied in many types of human cancer. Similarly, the presence of microsatellite instability (MSI) in the DNA mismatch repair system (hMSH2) may provide evidence of faulty DNA mismatch repair. One of the most important locations of MSI is the BAT26 gene. In addition, deranged serum cytokines, especially elevated levels of the tumor necrosis factor (TNF) alpha, have been found in many gynecological conditions.

Aims

The current study aimed at evaluating mutations in exons 6 and 7 of TP53 and the presence of microsatellite instability in BAT26 of the hMSH2 system in Egyptian patients with endometrial carcinoma. The study also evaluated whether there was a correlation between any of these genetic mutations/instability and the tissue expression of estrogen and progesterone receptors and the serum TNF-alpha level.

Patients and methods

The current study included 2 groups: a control group comprising 20 healthy women aged 52.21 ± 5.80 years attending the clinic for routine checkups and 40 patients with endometrial cancer aged 55.30 ± 6.21 years. Mutations in TP53 and BAT26 were evaluated using polymerase chain reaction–single-strand conformational polymorphism (PCR-SSCP) and automated sequencing while serum TNF-alpha was measured using an ELISA technique. Estrogen and progesterone receptor expression in biopsy tissue was evaluated using immunohistochemical staining.

Results

Seven of the 40 patients (17.5%) were positive for TP53 gene alterations in exon 6, while 9 patients (22.5%) were positive for TP53 alterations in exon 7. Cases positive for TP53 mutations had higher tumor stages. Ten patients (25%) showed MSI in BAT26. Nearly all patients with mutations in BAT26 had a strong family history for endometrial cancer (χ2=13.33, p<0.05). There was no positive correlation between the presence of MSI in the BAT26 gene and mutations in the TP53 gene or high serum TNF-alpha levels. Cases positive for TP53 mutations had a significantly higher level of TNF-alpha than cases negative for TP53 mutations (p<0.05). Cases showing mutations in exon 6 or 7 of TP53 showed a significantly higher intensity of immunohistochemical staining for estrogen and progesterone receptor expression in biopsy tissue than cases negative for mutations. (χ2=8.11, p<0.05).

Conclusion

Our results suggest that the development of endometrial carcinoma is probably mediated through a multi-step carcinogenesis pathway and mutation of TP53 does not necessarily result from the presence of microsatellite instability in BAT26. The high serum TNF-alpha levels detected in our patients may represent an immunological antitumor response that was particularly evident in cases positive for TP53 mutations.