Pro-angiogenic effects of MDM2 through HIF-1α and NF-κB mediated mechanisms in LNCaP prostate cancer cells

Resistance mechanisms to inhibitors of p53-MDM2 interactions in cancer therapy: can we overcome them?

Since the discovery of the first MDM2 inhibitors, we have gained deeper insights into the cellular roles of MDM2 and p53. In this review, we focus on MDM2 inhibitors that bind to the p53-binding domain of MDM2 and aim to disrupt the binding of MDM2 to p53. We describe the basic mechanism of action of these MDM2 inhibitors, such as nutlin-3a, summarise the determinants of sensitivity to MDM2 inhibition from p53-dependent and p53-independent points of view and discuss the problems with innate and acquired resistance to MDM2 inhibition. Despite progress in MDM2 inhibitor design and ongoing clinical trials, their broad use in cancer treatment is not fulfilling expectations in heterogenous human cancers. We assess the MDM2 inhibitor types in clinical trials and provide an overview of possible sources of resistance to MDM2 inhibition, underlining the need for patient stratification based on these aspects to gain better clinical responses, including the use of combination therapies for personalised medicine.

Synthetic curcumin analog: inhibiting the invasion, angiogenesis, and metastasis in human laryngeal carcinoma cells via NF-kB pathway

BACKGROUND

Laryngeal carcinoma, the most common among head and neck squamous cell carcinoma (HNSCC), induces 1% of all cancer deaths. Curcumin the active constituent of turmeric, is shown to be effective in the treatment of various cancers. In the present study, we explored the mechanistic role of bis-demethoxy curcumin analog (BDMC-A) as a chemotherapeutic agent. We investigated its inhibitory effect on invasion, angiogenesis, and metastasis in human laryngeal carcinoma (Hep-2) cells in comparison with curcumin.

METHODS

The effect of curcumin and BDMC-A on transcription factors (NF-κB, p65, c-Jun, c-Fos, STAT3, 5, PPAR-γ, β-catenin, COX-2, MMP-9, VEGF, TIMP-2) involved in signal transduction cascade, invasion, and angiogenesis in Hep-2 cells were quantified using Western blotting and RT-PCR technique. ELISA was used to measure the pro-inflammatory markers in Hep-2 cells treated with curcumin and BDMC-A.

RESULTS

The results showed that BDMC-A inhibits the transcription factors NF-κB, p65, c-Jun, c-Fos, STAT3, STAT5, PPAR-γ and β-catenin, which are responsible for tumor progression and malignancy. Moreover, BDMC-A treatment downregulated MMP-9, VEGF, TGF- β, IL-6 and IL-8 and upregulated TIMP-2 levels. The effects were more significant compared to curcumin.

CONCLUSION

Our overall results revealed that BDMC-A more effectively inhibited the markers of invasion, angiogenesis and metastasis in comparison with curcumin.

Prevention of prostate cancer by natural product MDM2 inhibitor GS25: in vitro and in vivo activities and molecular mechanisms

Prostate cancer remains a major health problem in the USA and worldwide. There is an urgent need to develop novel approaches to preventing primary and metastatic prostate cancer. We have identified 25-OCH3-protopanaxadiol (GS25), the most active ginsenoside that has been identified so far; it has potent activity against human cancers, including prostate cancer. However, it has not been proven if GS25 could be a safe and effective agent for cancer prevention. In this study, we used the TRAMP model and clearly demonstrated that GS25 inhibited prostate tumorigenesis and metastasis with minimal host toxicity. Mechanistically, GS25 directly bound to the RING domain of MDM2, disrupted MDM2-MDMX binding and induced MDM2 protein degradation, resulting in strong inhibition of prostate cancer cell growth and metastasis, independent of p53 and androgen receptor status. In conclusion, our in vitro and in vivo data support the potential use of GS25 in prevention of primary and metastatic prostate cancer.

XPD suppresses cell proliferation and migration via miR-29a-3p-Mdm2/PDGF-B axis in HCC

Objective

The aim of this study was to investigate the role of XPD in migration and invasion of hepatocellular carcinoma (HCC) cells.

Methods

The expression of XPD and miR-29a-3p was examined by western blot and qRT-PCR, cell proliferation was detected by MTT assay, cell migration was detected by transwell assay. TargetScan was used to predict potential targets of miR-29a-3p.

Results

In this study, we found that the expression of XPD and miR-29a-3p was downregulated in HCC samples and HCC cell lines. XPD suppressed proliferation and migration of HCC cell via regulating miR-29a-3p expression. Target prediction analysis and dual-luciferase reporter assay confirmed Mdm2 and PDGF-B were direct targets of miR-29a-3p, and miR-29a-3p suppressed proliferation and migration of HCC cells via regulating the expression of Mdm2 or PDGF-B.

Conclusions

Our data indicated that XPD suppressed cell proliferation and migration via miR-29a-3p-Mdm2/PDGF-B axis in HCC.

Novel allylated monocarbonyl analogs of curcumin induce mitotic arrest and apoptosis by reactive oxygen species-mediated endoplasmic reticulum stress and inhibition of STAT3

Curcumin is a promising active compound from a natural source and is extensively being tested in clinical trials because of its bio-functional properties. However, poor bioavailability has hampered its clinical application. Numerous attempts have been made in our laboratory to discover analogs of curcumin with enhanced bioavailability and superior pharmacological activity. In this study, we have investigated a new series of allylated monocarbonyl analogs of curcumin (MAC) and tested their effect on gastric cancer cells. Our results show six MAC that selectively targeted cancer cell lines to inhibit growth and induce apoptosis. This activity was achieved by generation of reactive oxygen species (ROS) by MAC. We selected one effective MAC (CA10) for further investigation and show that CA10 inhibits cell growth by causing G2/M cell cycle arrest and induction of apoptotic death. CA10 induced ROS generation and subsequent activation of endoplasmic reticulum (ER) stress and inhibition of signal transducer and activator of transcription 3 (STAT3) phosphorylation, inhibits cancer cell proliferation. These anti-tumor activities of CA10 were confirmed in gastric cancer xenografts. CA10 induced ROS, activated the ER stress pathway and inhibited STAT3 phosphorylation and gastric xenografts tumor growth in mice. Our studies provide experimental evidence that MAC CA10 effectively targets gastric cancer in preclinical models by enhancing ROS and ROS-mediated signaling.

The clinical and therapeutic uses of MDM2 and PSMA and their potential interaction in aggressive cancers

Prostate-specific membrane antigen (PSMA) overexpression is observed in the neovasculature of solid tumors, but not in the vasculature of normal tissues. Increased PSMA expression is positively associated with tumor stage and grade, although its function in cancer remains unclear. Mouse double minute 2 (MDM2) is a negative regulator of the p53 tumor suppressor and is reported to regulate VEGF expression and angiogenesis. Both proteins have been considered as biomarkers and therapeutic targets for advanced solid tumors. Our work and a recent microarray-based gene profiling study suggest there could be signaling interplay between MDM2 and PSMA. We herein review the mechanisms underlining the outgrowth of tumors associated with PSMA and MDM2, their potential interaction and how this may be applied to anticancer therapeutics.