Expression profile and prognostic importance in prostate lesions of the reverse transcriptase component of human telomerase (hTERT) and of cyclin-dependent kinase inhibitor p57 (p57kip2a)

Immunohistochemical expression of cyclin-dependent kinase inhibitors p16 and p57 in rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is a highly malignant cancer and is the most common soft tissue sarcoma in children and adolescents, but it is rare in adults (<1% of all adult malignancies). Altered expression and molecular abnormalities of cell-cycle-regulatory proteins are one of the most prominent features in RMS. Therefore, we evaluated the expression of cyclin-dependent kinase inhibitors p57 and p16, as well as p16 methylation status, along with clinicopathological characteristics and overall survival (OS) in RMS patients. This analysis was conducted on 23 pediatric and 44 adult patients. There was a male predominance in both groups and extremities were the most frequent tumor site. In adults, alveolar and pleomorphic types were almost equally represented. The majority of pediatric tumors were low grade, whereas, in adults, only one patient had a low-grade tumor. Seven pediatric (30.43%) and eight adult (18.18%) patients had a low p16 expression. The analysis of methylation status of the p16 promoter showed the presence of methylated allele only in one sample with pleomorphic histology. Six (26.1%) pediatric and 15 (34.1%) adult patients had low p57 expression, while in 17 (73.9%) pediatric and 29 (65.9%) adult patients it was assessed as high. Ninetyone percent of the pediatric patients and 32.6% of adults were alive at the end of the observational period. In adults, significant associations were found between OS and age (P = 0.020), gender (P = 0.027), tumor size (P < 0.001), lymph node status (P < 0.001), presence of metastases (P = 0.015), and p57 expression (P = 0.039). Stratification by histological type showed the correlation of low p57 expression (P = 0.030) and worse OS of patients with alveolar RMS. Univariate analysis identified age > 50 yrs. (HR 2.447), tumors > 5 cm (HR 21.31), involvement of regional lymph nodes (HR 3.96), the presence of metastases (HR 2.53), and low p57 expression (HR 2.11) as predictors of lower OS. Tumor size, regional lymph nodes involvement, and metastases were the independent predictors after multivariate analysis, while p57 did not predict OS in an independent way. In summary, although p57 was not confirmed to be an independent predictor of OS, our results indicate that its low expression may be the marker of aggressive phenotype and poor prognosis in adult RMS patients. Also, our findings suggest that epigenetic inactivation of p16 is not important in the pathogenesis of rhabdomyosarcoma.

hTERT, hTR and TERT promoter mutations as markers for urological cancers detection: A systematic review

The clinical relevance of telomerase subunits (human reverse transcriptase - hTERT, and human telomerase RNA - hTR) and TERT promotor mutations as biomarkers in genitourinary cancers was reviewed through the systematic analysis of the current literature. We performed a systematic literature search using 2 databases (Medline and Scopus) over the past 20 years. Primary outcomes were sensitivity and specificity of hTR, hTERT and TERT promoter mutations. Secondary outcomes were the biomarkers predictive values for tumor characteristics. Regarding bladder cancer, hTERT in urine showed high sensitivity (mean values: 55%-96%), and specificity (69%-100%): it correlated with bladder cancer grade and/or stage. hTR sensitivity ranged from 77% to 92%. With adapted cut-off, it demonstrated 72% to 89% specificity. TERT promoter mutation rate was up to 80% both in tissue and urine, resulting in 62%-92% sensitivity for primary tumors and 42% for relapse. Specificity ranged from 73% to 96%, no correlations with stage were observed. In prostate cancer, hTERT in tissue, prostate secretion and serum showed high sensitivity (97.9%, 36%, and 79.2%-97.5%, respectively) and specificity values (70%, 66%, 60%-100%). hTR showed very high sensitivity (88% in serum and 100% in tissue) although specificity values were highly variable depending on the series and techniques (0%-96.5%). In RCC, hTERT sensitivity on tissue ranged from 90 to 97%, specificity from 25 to 58%. There was an association of hTERT expression with tumor stage and grade. hTERT showed high accuracy in genitourinary cancers, while the value of hTR was more controversial. hTERT and TERT promotor mutations may have predictive value for bladder cancer and RCC staging and grading, while no such relationship was observed in CaP. Although telomerase subunits showed clinically relevant values in genitourinary cancers, developing fast and cost-effective methods is required before contemplating routine use.

Recombinant human decorin upregulates p57KIP² expression in HepG2 hepatoma cell lines

Increasing the expression of cyclin-cyclin-dependent kinase inhibitors (cyclin-CDK) using small molecule inhibitors is a therapeutic strategy used to suppress cancer cell growth. Decorin (DCN), a functional component of the extracellular matrix, has been implicated in the suppression of cell proliferation by upregulating p21, a cyclin-CDK inhibitor. The purpose of this study was to examine the effect of recombinant decorin on the reactivation of p57KIP2, whose expression is silenced in hepatocellular carcinoma (HCC). Cell viability assay, cell cycle analysis, apoptosis assay and quantitative real time-PCR experiments were performed in three groups of HepG2 human cells: Uninfected HepG2 cells (control group), pcDNA3.1 vector-infected HepG2 cells (pcDNA3.1 group) and pcDNA3.1-DCN-infected HepG2 cells (pcDNA3.1‑DCN group). Our results revealed that recombinant human decorin inhibited cell proliferation, induced G0/G1 phase arrest and induced apoptosis by increasing the expression of caspase-3 in the pcDNA3.1-DCN group. The expression of p57KIP2 mRNA in the pcDNA3.1-DCN group was higher than in the pcDNA3.1 and control groups (P<0.05); however, there was no statistically significant difference between the control and pcDNA3.1 groups (P>0.05). In conclusion, recombinant human decorin reactivated p57KIP2 expression in HepG2 cells. As the expression level of p57KIP2 is downregulated in HCC, our finding may serve as a basis for the therapy and prognosis of HCC, although further studies are required.

p57(KIP2) control of actin cytoskeleton dynamics is responsible for its mitochondrial pro-apoptotic effect

p57 (Kip2, cyclin-dependent kinase inhibitor 1C), often found downregulated in cancer, is reported to hold tumor suppressor properties. Originally described as a cyclin-dependent kinase (cdk) inhibitor, p57(KIP2) has since been shown to influence other cellular processes, beyond cell cycle regulation, including cell death and cell migration. Inhibition of cell migration by p57(KIP2) is attributed to the stabilization of the actin cytoskeleton through the activation of LIM domain kinase-1 (LIMK-1). Furthermore, p57(KIP2) is able to enhance mitochondrial-mediated apoptosis. Here, we report that the cell death promoting effect of p57(KIP2) is linked to its effect on the actin cytoskeleton. Indeed, whereas Jasplakinolide, an actin cytoskeleton-stabilizing agent, mimicked p57(KIP2)'s pro-apoptotic effect, destabilizing the actin cytoskeleton with cytochalsin D reversed p57(KIP2)'s pro-apoptotic function. Conversely, LIMK-1, the enzyme mediating p57(KIP2)'s effect on the actin cytoskeleton, was required for p57(KIP2)'s death promoting effect. Finally, p57(KIP2-)mediated stabilization of the actin cytoskeleton was associated with the displacement of hexokinase-1, an inhibitor of the mitochondrial voltage-dependent anion channel, from the mitochondria, providing a possible mechanism for the promotion of the mitochondrial apoptotic cell death pathway. Altogether, our findings link together two tumor suppressor properties of p57(KIP2), by showing that the promotion of cell death by p57(KIP2) requires its actin cytoskeleton stabilization function.

The hallmarks of CDKN1C (p57, KIP2) in cancer

Cyclin-dependent kinase inhibitor 1C CDKN1C (p57(KIP2)) regulates several hallmarks of cancer, including apoptosis, cell invasion and metastasis, tumor differentiation and angiogenesis. p57(KIP2) is generally not mutated in cancer, but its expression is downregulated through epigenetic changes such as DNA methylation and repressive histone marks at the promoter. This opens up possibilities for therapeutic intervention through reactivation of p57(KIP2) gene expression. Furthermore, p57(KIP2) has been tested as a prognostic factor for many types of cancer, even differentiating between early and late stage cancer. In this review, the multifunctional tumor suppressor capabilities of p57(KIP2), the mechanisms of p57(KIP2) transcriptional repression in cancer, and the therapeutic potential of reactivation of p57(KIP2) protein expression will be discussed.

Prognostic significance of co-expression of nm23 and p57 protein in hepatocellular carcinoma

AIM

  To investigate the unbalance of proliferation and apoptosis and the functions of cell-cycle proteins and apoptotic factor in metastasis of hepatocellular carcinoma (HCC) and their effect in prognosis.

METHODS

  Proliferation index and apoptosis index, as well as seven relatively molecular markers, namely p15, p34, p53, p57, p73, survivin and nm23, were evaluated by immunohistochemistry and TUNEL in HCC tissues and compared to adjacent non-cancerous tissues and normal liver tissues. Furthermore, the prognostic significance by follow-up and mutual relationships for each clinicopathologic factor and molecular marker were analysed.

RESULTS

  The dysregulation between proliferation and apoptosis and the abnormal expression of seven molecular markers were observed in HCC tissues. The unbalance of proliferation and apoptosis and abnormal expressions of p15, p34, p57 and nm23 were correlated with TNM stage and extrahepatic metastasis. In particular, the abnormal co-expression of nm23/p57 correlated with advanced TNM stage and bigger tumor size and was an independent prognostic factor of HCC.

CONCLUSION

  The unbalance of proliferation and apoptosis and abnormal expression of cell-cycle proteins promote metastasis of HCC. Moreover, the abnormal co-expression of nm23/p57 may be a useful molecular marker for metastasis and unfavourable prognosis for HCC.