Inverse correlation between p16INK4A expression and NF-kappaB activation in melanoma progression

CDKN2a/p16 Antagonizes Hepatic Stellate Cell Activation and Liver Fibrosis by Modulating ROS Levels

The lipid-storage hepatic stellate cells (HSC) play as pivotal role in liver fibrosis being able to trans-differentiate into myofibroblasts in response to various pro-fibrogenic stimuli. In the present study we investigated the role of CDKN2a/p16, a negative regulator of cell cycling, in HSC activation and the underlying mechanism. Levels of p16 were significantly down-regulated in activated HSCs isolated from mice induced to develop liver fibrosis compared to quiescent HSCs isolated from the control mice ex vivo. There was a similar decrease in p16 expression in cultured HSCs undergoing spontaneous activation or exposed to TGF-β treatment in vitro. More important, p16 down-regulation was observed to correlate with cirrhosis in humans. In a classic model of carbon tetrachloride (CCl₄) induced liver fibrosis, fibrogenesis was far more extensive in mice with p16 deficiency (KO) than the wild type (WT) littermates. Depletion of p16 in cultured HSCs promoted the synthesis of extracellular matrix (ECM) proteins. Mechanistically, p16 deficiency accelerated reactive oxygen species (ROS) generation in HSCs likely through the p38 MAPK signaling. P38 inhibition or ROS cleansing attenuated ECM production in p16 deficient HSCs. Taken together, our data unveil a previously unappreciated role for p16 in the regulation of HSC activation. Screening for small-molecule compounds that can boost p16 activity may yield novel therapeutic strategies against liver fibrosis.

P16-specific DNA methylation by engineered zinc finger methyltransferase inactivates gene transcription and promotes cancer metastasis

Background

P16 DNA methylation is well known to be the most frequent event in cancer development. It has been reported that genetic inactivation of P16 drives cancer growth and metastasis, however, whether P16 DNA methylation is truly a driver in cancer metastasis remains unknown.

Results

A P16-specific DNA methyltransferase (P16-dnmt) expression vector is designed using a P16 promoter-specific engineered zinc finger protein fused with the catalytic domain of dnmt3a. P16-dnmt transfection significantly decreases P16 promoter activity, induces complete methylation of P16 CpG islands, and inactivates P16 transcription in the HEK293T cell line. The P16-Dnmt coding fragment is integrated into an expression controllable vector and used to induce P16-specific DNA methylation in GES-1 and BGC823 cell lines. Transwell assays show enhanced migration and invasion of these cancer cells following P16-specific DNA methylation. Such effects are not observed in the P16 mutant A549 cell line. These results are confirmed using an experimental mouse pneumonic metastasis model. Moreover, enforced overexpression of P16 in these cells reverses the migration phenotype. Increased levels of RB phosphorylation and NFκB subunit P65 expression are also seen following P16-specific methylation and might further contribute to cancer metastasis.

Conclusion

P16 methylation could directly inactivate gene transcription and drive cancer metastasis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13059-015-0819-6) contains supplementary material, which is available to authorized users.

Immunohistochemical expression of p16, p21, p27 and cyclin D1 in oral nevi and melanoma

The acquisition of abnormalities at G1/S is considered a crucial step in the genesis and progression of melanoma. The expression of cell cycle regulators has also been used in various neoplasms as an adjunct to diagnosis. The aim of this study was to compare the expression of p16, p21, p27 and cyclin D1 in oral nevi and melanomas. Expression of these cell cycle regulatory proteins was evaluated by immunohistochemistry in 51 oral melanocytic lesions, including 38 intramucosal nevi and 13 primary oral melanomas. p16 and p27 were highly expressed in intramucosal nevi, whereas p21 and cyclin D1 expression was higher in oral melanomas. The results indicate that p21 and cyclin D1 may be involved in the development of oral melanomas, and eventually they may be useful in the differential diagnoses of oral benign and malignant melanocytic lesions.

The diverse and complex roles of NF-κB subunits in cancer

It is only recently that the full importance of nuclear factor-κB (NF-κB) signalling to cancer development has been understood. Although much attention has focused on the upstream pathways leading to NF-κB activation, it is now becoming clear that the inhibitor of NF-κB kinases (IKKs), which regulate NF-κB activation, have many independent functions in tissue homeostasis and normal immune function that could compromise the clinical utility of IKK inhibitors. Therefore, if the NF-κB pathway is to be properly exploited as a target for both anticancer and anti-inflammatory drugs, it is appropriate to reconsider the complex roles of the individual NF-κB subunits.

High frequency of p16(INK4A) promoter methylation in NRAS-mutated cutaneous melanoma

The p16(INK4A) tumor suppressor is often deleted, or otherwise inactivated, in malignant melanoma. To investigate the loss of p16(INK4A) in greater detail, we analyzed 77 cutaneous melanoma metastases. Of these 56 retained at least one p16(INK4A) allele, and 21 had biallelic deletions. Using methylation-specific PCR, direct sequencing, and immunohistochemical methods, we analyzed p16(INK4A) promoter methylation, mutations, and protein expression, respectively. In addition, 14 corresponding primary tumors were analyzed for protein expression. Results were compared to clinicopathological parameters and previously obtained data regarding mutations in proto-oncogenes NRAS and BRAF. Results revealed that p16(INK4A) promoter methylation was present in 15 of 59 (25%) metastases; nonsynonymous mutations in 9 of 56 (16%) metastases; and protein expression in 12 of 67 (18%) metastases. Protein expression was lost during progression from primary to metastatic tumors, 71% (10 of 14) and 43% (6 of 14) being positive, respectively. However, the genetic and epigenetic alterations of p16(INK4A) observed could not explain the lack of p16(INK4A) protein in 27 metastases, indicating the presence of additional inactivating mechanisms for p16(INK4A). Interestingly, p16(INK4A) promoter methylation was significantly overrepresented in NRAS-mutated samples compared to NRAS wild-type samples (P=0.0004), indicating an association between these two events.

NF-kappaB as a molecular target in the therapy of pancreatic carcinoma

The constitutive activation of the transcription factor nuclear-factor kappa B (NF-kappaB) is a hallmark of many highly malignant tumours such as the pancreatic ductal adenocarcinoma and accounts for profound chemoresistance. Inhibition of NF-kappaB activation has been shown to be a useful strategy for increasing the sensitivity towards cytostatic drug treatment in vitro and in vivo. Moreover, various pharmacological substances (e.g. thalidomide, bortezomib, sulphasalazine) have already entered clinical studies partially showing promising results for certain types of cancer. Further studies will be needed, in particular for pancreatic ductal adenocarcinoma, to evaluate the therapeutic efficacy of appropriate combinations of a NF-kappaB inhibitor and cytostatic drugs.

Cell cycle and apoptosis regulators in Spitz nevi: comparison with melanomas and common nevi

BACKGROUND

Deregulated cell cycle control is one of the hallmarks of tumor development. The expression of different cell cycle regulators has been used in various neoplasms as an adjunct to diagnosis.

OBJECTIVE

We sough to determine the expression of cell cycle and apoptosis regulators in Spitz nevi and to appraise its value as a diagnostic adjunct in the differential diagnosis from melanomas and common nevi.

METHODS

Ki-67, p-27, p-16, p-53, p-21, Rb, cyclin D1, cyclin A, cyclin B1, bcl-2, and bax expression was assessed by immunohistochemistry in 10 Spitz nevi and was compared with 16 melanomas and 20 common nevi immunohistochemical expression.

RESULTS

P-27 (60% +/- 20.13), p-16 (62.00% +/- 10.85), and bcl-2 (46.00% +/- 42.47) were highly expressed in Spitz nevi, whereas Ki-67 (2.80% +/- 2.55), Rb (3.75% +/- 4.55), p-53 (2.30% +/- 0.10), cyclin A (0.70% +/- 1.56), B1 (0.20% +/- 0.34), and bax (2.65% +/- 6.37) demonstrated a limited expression. Cyclin D1 (8.60% +/- 7.30) and p-21 (6.40% +/- 5.37) showed a moderate expression. The expression of bax (P = .001), Ki-67 (P < .0001), Rb (P < .0001), p-16 (P < .0001), cyclin A (P < .0001), and cyclin B1 (P < .0001) was significantly higher in melanomas in comparison with Spitz nevi, whereas p-27 expression was significantly higher in Spitz nevi (P < .0001). A trend for significant difference in favor of melanomas was also observed for p-53 (P = .002). On the other hand, no difference was detected for bcl-2 (P = .275), p-21 (P = .055), or cyclin D1 (P = .077). Spitz nevi demonstrated a trend for a higher expression for p-21 (P = .008) and cyclin D1 (P = .006), whereas they exhibited lower p-16 (P = .004) in comparison with common nevi.

LIMITATIONS

The number of Spitz nevi was relatively small.

CONCLUSION

Spitz nevi differ from melanomas in their immunohistochemical pattern of expression of cell cycle and apoptosis regulators and more closely resemble common benign nevi.

Expression of nuclear factor kappaB in human gastric carcinoma: relationship with I kappaB a and prognostic significance

Nuclear factor (NF)-kappaB is a transcription factor constitutively activated in various neoplasms, including gastric carcinoma. However, its clinical significance in the latter remains an unresolved issue, as published information is limited and controversial. Furthermore, no data is available about the interaction of NF kappaB with its inhibitory protein I kappaB a in gastric carcinoma cases. In this study, the expression of NF kappaB 1/p50 and p I kappaB a protein was evaluated immunohistochemically in paraffin-embedded tissues from 93 patients. The effect of NF kappaB 1/p50 and p I kappaB a on clinical outcome was assessed. Positive immunostaining was detected for nuclear NF kappaB 1/p50, cytoplasmic NF kappa B1/p50 and p I kappaB a in 91, 68 and 85.7% of cases, respectively. A positive correlation emerged between nuclear NF kappa B 1/p50 and p I kappaB a (p < 0.0001) and a negative one between cytoplasmic NF kappaB 1/p50 and p I kappaB a (p = 0.0033). Nuclear NF kappaB 1/p50 was associated with stage (p = 0.0388), the depth of invasion (p = 0.0382), World Health Organization (WHO; p = 0.0326) and Lauren's histological classification (p = 0.0046). NF kappaB 1/p50 nuclear expression adversely affected survival in both univariate and multivariate analysis (p < 0.0001 and p = 0.02, respectively). Our results suggest that NF kappaB 1/p50 nuclear expression and therefore activation is regulated by its interaction with I kappaB a and that the former may serve as a useful independent molecular marker for stratifying patients with gastric carcinoma in terms of prognosis.

Coordinated upregulation of COX-2 and NF-kappaB is a steady feature of laryngeal carcinogenesis

BACKGROUND/AIMS

Laryngeal cancer is the endpoint of a multistage process involving hyperplastic and dysplastic lesions, not adequately defined in their molecular aspect. Our objective was to evaluate the expression of the prostaglandin-synthesizing enzyme cyclooxygenase-2 (COX-2) and the chief transcription factor nuclear factor-kappaB (NF-kappaB) in laryngeal carcinomas and their precursors, as well as to explore any association between the two molecules.

METHODS

We performed paraffin section immunohistochemistry for COX-2 and the p65 subunit of NF-kappaB, in tissues from 129 patients with tumors or premalignancies. p65 cytoplasmic and nuclear immunostaining were listed individually.

RESULTS

COX-2 was positively correlated with histopathological grading from normal mucosa to carcinomas (Spearman's coefficient r(s) = 0.286, p < 0.001). No association was revealed between COX-2 expression and tumor grade. p65 immunoreactivity, both of cytoplasmic and nuclear origin, increased along the carcinogenesis course, manifesting highest expression in invasive cancer (r(s) = 0.419, p < 0.001 and r(s) = 0.241, p < 0.001, respectively). Again, tumor grade had no influence on expression. COX-2 and p65 cytoplasmic, but no nuclear, expression showed a positive correlation (r(s) = 0.352, p < 0.001).

CONCLUSIONS

This study demonstrates that lesional advance in the larynx towards cancer is marked by ongoing upregulation of COX-2 and NF-kappaB. Synchronism between individual expressions may denote a regulatory role of the latter in COX-2 transactivation.

Good cop, bad cop: the different faces of NF-kappaB

Complexes formed from the nuclear factor kappaB (NF-kappaB) family of transcription factors are ubiquitously expressed and are induced by a diverse array of stimuli. This results in their becoming activated in a wide variety of different settings. While the functions of NF-kappaB in many of these contexts have been the subject of intense research and are now well established, it is also clear that there is great diversity in the effects and consequences of NF-kappaB activation. NF-kappaB subunits do not necessarily regulate the same genes, in an identical manner, in all of the different circumstances in which they are induced. This review will discuss the different functions of NF-kappaB, the pathways that modulate NF-kappaB subunit activity and, in contrast to its more commonly thought of role as a promoter of cancer cell growth and survival, the ability of NF-kappaB, under some circumstances, to behave as a tumor suppressor.