Chimeras of p14ARF and p16: functional hybrids with the ability to arrest growth

LncRNA CAI2 Contributes to Poor Prognosis of Glioma through the PI3K-Akt Signaling Pathway

AIMS

We aim to explore new potential therapeutic targets and markers in human glioma.

BACKGROUND

Gliomas are the most common malignant primary tumor in the brain.

OBJECTIVE

In the present research, we evaluated the effect of CAI2, a long non-coding RNA, on the biological behaviors of glioma and explored the related molecular mechanism.

METHODS

The expression of CAI2 was analyzed using qRT-PCR in 65 cases of glioma patients. The cell proliferation was determined with MTT and colony formation assays, and the PI3K-AKt signaling pathway was analyzed using western blot.

RESULTS

CAI2 was upregulated in human glioma tissue compared with the matched, adjacent nontumor tissue and was correlated with WHO grade. Survival analyses proved that the overall survival of patients with high CAI2 expression was poor compared to that of patients with low CAI2 expression. High CAI2 expression was an independent prognostic factor in glioma. The absorbance values in the MTT assay after 96 h were .712 ± .031 for the si-control and .465 ± .018 for the si- CAI2-transfected cells, and si-CAI2 inhibited colony formation in U251 cells by approximately 80%. The levels of PI3K, p-AKt, and AKt in si-CAI2-treated cells were decreased.

CONCLUSION

CAI2 may promote glioma growth through the PI3K-AKt signaling pathway. This research provided a novel potential diagnostic marker for human glioma.

The functional role of inherited CDKN2A variants in childhood acute lymphoblastic leukemia

OBJECTIVE

Genetic alterations in CDKN2A tumor suppressor gene on chromosome 9p21 confer a predisposition to childhood acute lymphoblastic leukemia (ALL). Genome-wide association studies have identified missense variants in CDKN2A associated with the development of ALL. This study systematically evaluated the effects of CDKN2A coding variants on ALL risk.

METHODS

We genotyped the CDKN2A coding region in 308 childhood ALL cases enrolled in CCCG-ALL-2015 clinical trials by Sanger Sequencing. Cell growth assay, cell cycle assay, MTT-based cell toxicity assay, and western blot were performed to assess the CDKN2A coding variants on ALL predisposition.

RESULTS

We identified 10 novel exonic germline variants, including 6 missense mutations (p.A21V, p.G45A and p.V115L of p16INK4A; p.T31R, p.R90G, and p.R129L of p14ARF) and 1 nonsense mutation and 1 heterozygous termination codon mutation in exon 2 (p16INK4A p.S129X). Functional studies indicate that five novel variants resulted in reduced tumor suppressor activity of p16INK4A, and increased the susceptibility to the leukemic transformation of hematopoietic progenitor cells. Compared to other variants, p.H142R contributes higher sensitivity to CDK4/6 inhibitors.

CONCLUSION

These findings provide direct insight into the influence of inherited genetic variants at the CDKN2A coding region on the development of ALL and the precise clinical application of CDK4/6 inhibitors.

Effects of the p16/cyclin D1/CDK4/Rb/E2F1 pathway on aberrant lung fibroblast proliferation in neonatal rats exposed to hyperoxia

p16^INK4a (p16) inhibits the vital G₁ to S phase transition during cell cycle progression through the p16/cyclin D1/CDK4/retinoblastoma(Rb)/E2F1 pathway. Hyperoxia can suppress the G₁/S checkpoint and induce more lung fibroblasts (LFs) to transition from the G₁ phase to the S phase and undergo cell proliferation. The present study investigated the rate of p16 gene promoter methylation and the protein expression levels of p16, cyclin D1, CDK4, Rb and E2F1 in LFs from the lungs of rats exposed to hyperoxia and normoxia on postnatal days 3, 7 and 14. In the hyperoxia-exposed group, the methylation rate was 50 and 80% on days 7 and 14, respectively. Cyclin D1 and CDK4 overexpression was associated with p16 loss and Rb inactivation by phosphorylation. Rb phosphorylation induced E2F1 release in the G₁ phase, which promoted cell proliferation. No methylation was observed in the normoxia-exposed group. These observations suggested that p16 loss may stimulate aberrant LF proliferation via the p16/cyclin D1/CDK4/Rb/E2F1 pathway.

Determinants of p14/ARF methylation in healthy females: association with reproductive and non-reproductive risk factors of breast cancer

Background

DNA methylation is associated with the risk factors of breast cancer. However, the impact of the reproductive and non-reproductive risk factors of breast cancer on p14/ARF methylation is not well known. Therefore, we investigated the relationships between p14/ARF methylation percentage and risk factors of breast cancer including age, family history, obesity, and reproductive risk factors in 120 breast cancer-free subjects; 60 women with a first-degree family history of breast cancer and 60 age-matched women with no family history of breast cancer. Extracted DNA from the whole blood was bisulfite-treated by EZ DNA modification kit. Quantitative methylation of p14/ARF was analyzed by methylation-specific PCR then methylation percentage of p14/ARF was calculated.

Results

P14/ARF methylation percentage was not related to any of the risk factors of breast cancer except age. Our study showed that p14/ARF methylation percentage was significantly higher in females with age ≥ 40 years than in females with age <  40 years (p=0.029). Also, a positive significant correlation between the p14/ARF methylation percentage and age was detected (r = 0.285, p = 0.014). Furthermore, univariate regression analysis showed that the age is independently associated with high p14/ARF methylation percentage (β = 1. 46, p = 0.029).

Conclusion

Among healthy females, the age is strongly linked to the peripheral p14/ARF methylation percentage. The present study suggests that p14/ARF methylation is not associated with other breast cancer risk factors. These results need oncoming research on a large cohort to define the interactions between p14/ARF methylation and the risk factors of breast cancer.

ECRG4 acts as a tumor suppressor gene frequently hypermethylated in human breast cancer

Human breast cancer is a malignant form of tumor with a relatively high mortality rate. Although esophageal cancer-related gene 4 (ECRG4) is thought to be a possible potent tumor suppressor gene that acts to suppress breast cancer, its precise role in this disease is not understood. Herein, we assess the correlation between ECRG4 expression and DNA methylation, probing the potential epigenetic regulation of ECRG4 in breast cancer. We analyzed ECRG4 promoter methylation via methylation-specific PCR (MSPCR), bisulfite sequencing, and a promoter reporter assay in human breast cancer cell lines and samples. Gene expression was assessed by quantitative real-time PCR (qPCR), while protein levels were assessed by Western blotting. CCK8 assays were used to quantify cell growth; Esophageal cancer-related gene 4 wound healing assays were used to assess cellular migration, while flow cytometry was used to assess apoptosis and cell cycle progression. Apoptosome formation was validated via CO-IP and Western blotting. We found that human breast cancer samples exhibited increased methylation of the ECRG4 promoter and decreased ECRG4 expression. Remarkably, the down-regulation of ECRG4 was highly associated with promoter methylation, and its expression could be re-activated via 5-aza-2′-deoxycytidine treatment to induce demethylation. ECRG4 overexpression impaired breast cancer cell proliferation and migration, and led to G0/G1 cell cycle phase arrest. Moreover, ECRG4 induced the formation of the Cytc/Apaf-1/caspase-9 apoptosome and promoted breast cancer cell apoptosis. ECRG4 is silenced in human breast cancer cells and cell lines, likely owing to promoter hypermethylation. ECRG4 may act as a tumor suppressor, inhibiting proliferation and migration, inducing G0/G1 phase arrest and apoptosis via the mitochondrial apoptotic pathway.

The efficacy of HRAS and CDK4/6 inhibitors in anaplastic thyroid cancer cell lines

PURPOSE

Anaplastic thyroid carcinomas (ATCs) are non-responsive to multimodal therapy, representing one of the major challenges in thyroid cancer. Previously, our group has shown that genes involved in cell cycle are deregulated in ATCs, and the most common mutations in these tumours occurred in cell proliferation and cell cycle related genes, namely TP53, RAS, CDKN2A and CDKN2B, making these genes potential targets for ATCs treatment. Here, we investigated the inhibition of HRAS by tipifarnib (TIP) and cyclin D-cyclin-dependent kinase 4/6 (CDK4/6) by palbociclib (PD), in ATC cells.

METHODS

ATC cell lines, mutated or wild type for HRAS, CDKN2A and CDKN2B genes, were used and the cytotoxic effects of PD and TIP in each cell line were evaluated. Half maximal inhibitory concentration (IC50) values were determined for these drugs and its effects on cell cycle, cell death and cell proliferation were subsequently analysed.

RESULTS

Cell culture studies demonstrated that 0.1 µM TIP induced cell cycle arrest in the G2/M phase (50%, p < 0.01), cell death, and inhibition of cell viability (p < 0.001), only in the HRAS mutated cell line. PD lowest concentration (0.1 µM) increased significantly cell cycle arrest in the G0/G1 phase (80%, p < 0.05), but only in ATC cell lines with alterations in CDKN2A/CDKN2B genes; additionally, 0.5 µM PD induced cell death. The inhibition of cell viability by PD was more pronounced in cells with alterations in CDKN2A/CDKN2B genes (p < 0.05) and/or cyclin D1 overexpression.

CONCLUSIONS

This study suggests that TIP and PD, which are currently in clinical trials for other types of cancer, may play a relevant role in ATC treatment, depending on the specific tumour molecular profile.

Aberrant Expression of p14ARF in Human Cancers: A New Biomarker?

The ARF and INK4a genes are located on the CDKN2a locus, both showing tumor suppressive activity. ARF has been shown to monitor potentially harmful oncogenic signalings, making early stage cancer cells undergo senescence or programmed cell death to prevent cancer. Conversely, INK4a detects both aging and incipient cancer cell signals, and thus these two gene functions are different. The efficiency of detection of oncogenic signals is more efficient for the for the former than the latter in the mouse system. Both ARF and INK4a genes are inactivated by gene deletion, promoter methylation, frame shift, aberrant splicing although point mutations for the coding region affect only the latter. Recent studies show the splicing alterations that affect only ARF or both ARF and INK4a genes suggesting that ARF is inactivated in human tumors more frequently than what was previously thought. The ARF gene is activated by E2Fs and Dmp1 transcription factors while it is repressed by Bmi1, Tbx2/3, Twist1, and Pokemon nuclear proteins. It is also regulated at protein levels by Arf ubiquitin ligase named ULF, MKRN1, and Siva1. The prognostic value of ARF overexpression is controversial since it is induced in early stage cancer cells to eliminate pre-malignant cells (better prognosis); however, it may also indicate that the tumor cells have mutant p53 associated with worse prognosis. The ARF tumor suppressive protein can be used as a biomarker to detect early stage cancer cells as well as advanced stage tumors with p53 inactivation.

Anticarcinogenic effects of water extract of sporoderm-broken spores of Ganoderma lucidum on colorectal cancer in vitro and in vivo

Ganoderma lucidum (G. lucidum) polysaccharides (GLPs) have been used as traditional Chinese medicine for cancer prevention for many years. However, the mechanism by which GLP exerts its chemopreventive activities remains elusive. In addition, it is unclear whether sporoderm-broken spores of G. lucidum water extract (BSGLWE), which contains mainly GLPs, has anticancer effects on colorectal cancer. The present study investigated the anticancer effects and potential mechanisms of BSGLWE on colorectal cancer in vivo and in vitro. Our results showed that BSGLWE significantly inhibited colorectal cancer HCT116 cell viability in a time- and dose-dependent manner. Flow cytometry analysis indicated that BSGLWE disrupted cell cycle progression at G2/M phase via downregulation of cyclin B1 and cyclin A2, and upregulation of P21 at mRNA levels. Moreover, BSGLWE induced apoptosis by decreasing Bcl-2 and survivin at mRNA levels, and reduced Bcl-2, PARP, pro-caspase-3 and pro-caspase-9 at protein levels. Furthermore, BSGLWE suppressed tumor growth in vivo by regulating the expression of genes and proteins associated with cell cycle and apoptosis, which was further confirmed by a reduction of Ki67, PCNA, and Bcl-2 expression as determined by immunohistochemistry staining. NSAID activated gene-1 (NAG-1), a pro-apoptotic gene, was significantly upregulated in vivo and in vitro upon BSGLWE treatment at both mRNA and protein levels. In addition, the relative amounts of secreted NAG-1 in cell culture medium or serum of nude mice were all upregulated upon BSGLWE treatments, suggesting a role of NAG-1 in BSGLWE-induced anticolorectal cancer activity. This is the first study to show that BSGLWE inhibits colorectal cancer carcinogenesis through regulating genes responsible for cell proliferation, cell cycle and apoptosis cascades. These findings indicate that BSGLWE possesses chemopreventive potential in colorectal cancer which may serve as a promising anticancer agent for clinical applications.

[Effects and mechanism of the circadian clock gene Per1 on the proliferation, apoptosis, cycle, and tumorigenicity in vivo of human oral squamous cell carcinoma]

OBJECTIVE

To determine the regulatory effects of the circadian clock gene Per1 on cell cycle-related genes and its influence on the proliferation, apoptosis, cycle, and tumorigenicity in vivo of human oral squamous cell carcinoma SCC15 cells.

METHODS

Three groups of the short hairpin RNA (shRNA) of lentivirus recombinant plasmids were designed against the RNA of Per1 and then transfected to the SCC15 cells. The optimum interference group was screened through Western blot and quantitative real-time PCR (qRT-PCR) and assigned as the experimental group. The transfected lentivirus plasmid without an interference effect on any gene was set as the control group (Control-shRNA). Untreated SCC15 cells were set as the blank group. The mRNA expressions of cell cycle-related genes, namely, Per1, p53, Cyclin D1, Cyclin E, Cyclin A2, Cyclin B1, CDK1, CDK2, CDK4, CDK6, p16, p21, Wee1, cdc25, E2F, and Rbl1 in each group were detected through qRT-PCR. The cell proliferation, apoptosis, and cell cycle distribution in each group were evaluated through flow cytometry. The cells of the experimental group and the blank group were subcutaneously inoculated in nude mice to observe tumorigenesis.

RESULTS

Three groups of Per1-shRNA lentivirus plasmids were constructed successfully. Among the groups, the Per1-shRNA- I group exhibited the highest interference effect, as indicated by qRT-PCR and Western blot analysis. As such, this group was set as the experimental group. The mRNA expression levels of CyclinD1, CyclinE, CyclinB1, CDK1, and Wee1 gene in the Per1-shRNA-I group were significantly higher than those in the Control-shRNA group and the SCC15 group (P < 0.05). By contrast, the mRNA expression levels of p53, Cyclin A2, p16, p21, and cdc25 in the Per1-shRNA-I group were significantly lower than those in the Control-shRNA group and the SCC15 group (P < 0.05). The mRNA expression levels of each gene between the Control-sLRNA group and the SCC15 group did not significantly differ (P > 0.05). The mRNA expression levels of CDK2, CDK4, CDK6, E2F, and Rb1 did not significantly differed in the three groups (P > 0.05). The proliferation index of the Perl-shRNA-I group was significantly higher than those of the Control-shRNA group and the SCC15 group (P < 0.05). The apoptosis index of the Per1-shRNA-I group was significantly lower than those of the Control-shRNA group and the SCC15 group (P < 0.05). The number of S-phase cells in the Per1-shRNA-I group was significantly lower than those of S-phase cells in the Control-shRNA group and the SCC15 group (P < 0.05). The number of G2/M-phase cells in the Per1-shRNA-I group was significantly higher than those of G2/M-phase cells in the Control-shRNA group and the SCC15 group (P < 0.05). Conversely, the proliferation index, apoptotic index, and cell cycle distribution of the cells in the Control-shRNA group did not significantly differ from those of the SCC15 group (P > 0.05). The tumorigenic ability in vivo was significantly enhanced in the Per1-shRNA-I group (P < 0.05).

CONCLUSION

Per1 is an important tumor suppressor gene. Per1 can regulate a large number of downstream cell cycle-related genes. The alteration of its expression can affect cell cycle progression, proliferation, apoptosis imbalance, and tumorigenic ability in vivo. Further studies on Per1 may elucidate cancer development and provide novel effective molecular targets for cancer treatment.

The important tumor suppressor role of PER1 in regulating the cyclin-CDK-CKI network in SCC15 human oral squamous cell carcinoma cells

BACKGROUND

Accumulating evidence suggests that the abnormal expression of the circadian clock gene PER1 is closely related to the development and progression of cancer. However, the exact molecular mechanism by which the abnormal expression of PER1 induces carcinogenesis is unclear. This study was conducted to investigate the alterations in downstream cell cycle genes, cell cycle distribution, cell proliferation, apoptosis, and in vivo tumorigenicity in SCC15 oral squamous cell carcinoma cells after PER1 downregulation.

MATERIALS AND METHODS

A stable SCC15 cell line was established to constitutively express shRNA targeting PER1. Quantitative real-time polymerase chain reaction (PCR) and Western blot analyses were conducted to estimate PER1 mRNA and protein expression. The expression of PER1, P53, CyclinD1, CyclinE, CyclinA2, CyclinB1, cyclin-dependent kinase (CDK) 1, CDK2, CDK4, CDK6, P16, P21, WEE1, and CDC25 mRNA was detected by quantitative real-time PCR. Cell cycle distribution, cell proliferation, and apoptosis were determined by flow cytometry. The in vivo tumorigenicity of SCC15 cells was evaluated in female BALB/c nu/nu mice.

RESULTS

PER1 downregulation resulted in significantly increased mRNA expression levels of CyclinD1, CyclinE, CyclinB1, CDK1, and WEE1 (P<0.05), and significantly decreased mRNA expression levels of P53, CyclinA2, P16, P21, and CDC25 (P<0.05) compared to control cells. Additionally, PER1 downregulation led to significantly fewer cells in S phase (P<0.05), but significantly more cells in G2/M phase (P<0.05) compared to the control group. After PER1 downregulation, the cell proliferation index was significantly higher (P<0.05), and the apoptotic index was significantly lower (P<0.05). The in vivo tumorigenicity of SCC15 cells was significantly enhanced by PER1 downregulation (P<0.05).

CONCLUSION

PER1 is an important tumor suppressor gene which acts by regulating the Cyclin-CDK-cyclin-dependent kinase inhibitor regulatory network. An in-depth characterization of this gene may further illuminate the molecular mechanisms responsible for the development and progression of cancer, thus providing novel molecular targets for cancer treatment.

Clinicopathological significance of p16, cyclin D1, Rb and MIB-1 levels in skull base chordoma and chondrosarcoma

Objective

To investigate the expression of p16, cyclin D1, retinoblastoma tumor suppressor protein (Rb) and MIB-1 in skull base chordoma and chondrosarcoma tissues, and to determine the clinicopathological significance of the above indexes in these diseases.

Methods

A total of 100 skull base chordoma, 30 chondrosarcoma, and 20 normal cartilage tissue samples were analyzed by immunohistochemistry. The expression levels of p16, cyclinD1, Rb and MIB-1 proteins were assessed for potential correlation with the clinicopathological features.

Results

As compared to normal cartilage specimen (control), there was decreased expression of p16, and increased expression of cyclin D1, Rb and MIB-1 proteins, in both skull base chordoma and chondrosarcoma specimens. MIB-1 LI levels were significantly increased in skull base chordoma specimens with negative expression of p16, and positive expression of cyclin D1 and Rb (P < 0.05). Significantly elevated MIB-1 LI was also detected in skull base chondrosarcoma tissues, while there was negative expression of p16, cyclin D1 and Rb (P < 0.05). In skull base chordoma, p16 negatively correlated with cyclin D1 and Rb, while cyclin D1 positively correlated with Rb. Additionally, p16, cyclin D1, Rb, or MIB-1 expression showed no correlation with age, gender, or pathological classification of patients with skull base chordoma (P > 0.05). However, p16 and MIB-1 levels correlated with the intradural invasion, and expression of p16, Rb and MIB-1 correlated with the number of tumor foci (P < 0.05). Further, the expression of p16 and MIB-1 appeared to correlate with the prognosis of patients with skull base chordoma.

Conclusions

The abnormal expression of p16, cyclin D1 and Rb proteins might be associated with the tumorigenesis of skull base chordoma and chondrosarcoma.

High expression of CAI2, a 9p21-embedded long noncoding RNA, contributes to advanced-stage neuroblastoma

Neuroblastoma is a pediatric cancer with significant genomic and biologic heterogeneity. p16 and ARF, two important tumor-suppressor genes on chromosome 9p21, are inactivated commonly in most cancers, but paradoxically overexpressed in neuroblastoma. Here, we report that exon γ in p16 is also part of an undescribed long noncoding RNA (lncRNA) that we have termed CAI2 (CDKN2A/ARF Intron 2 lncRNA). CAI2 is a single-exon gene with a poly A signal located in but independent of the p16/ARF exon 3. CAI2 is expressed at very low levels in normal tissue, but is highly expressed in most tumor cell lines with an intact 9p21 locus. Concordant expression of CAI2 with p16 and ARF in normal tissue along with the ability of CAI2 to induce p16 expression suggested that CAI2 may regulate p16 and/or ARF. In neuroblastoma cells transformed by serial passage in vitro, leading to more rapid proliferation, CAI2, p16, and ARF expression all increased dramatically. A similar relationship was also observed in primary neuroblastomas where CAI2 expression was significantly higher in advanced-stage neuroblastoma, independently of MYCN amplification. Consistent with its association with high-risk disease, CAI2 expression was also significantly associated with poor clinical outcomes, although this effect was reduced when adjusted for MYCN amplification. Taken together, our findings suggested that CAI2 contributes to the paradoxical overexpression of p16 in neuroblastoma, where CAI2 may offer a useful biomarker of high-risk disease.