Crosstalk between PI3K and Ras pathways via protein phosphatase 2A in human ovarian clear cell carcinoma

Protein serine/threonine phosphatases in tumor microenvironment: a vital player and a promising therapeutic target

The tumor microenvironment (TME) is involved in cancer initiation and progression. With advances in the TME field, numerous therapeutic approaches, such as antiangiogenic treatment and immune checkpoint inhibitors, have been inspired and developed. Nevertheless, the sophisticated regulatory effects on the biological balance of the TME remain unclear. Decoding the pathological features of the TME is urgently needed to understand the tumor ecosystem and develop novel antitumor treatments. Protein serine/threonine phosphatases (PSPs) are responsible for inverse protein phosphorylation processes. Aberrant expression and dysfunction of PSPs disturb cellular homeostasis, reprogram metabolic processes and reshape the immune landscape, thereby contributing to cancer progression. Some therapeutic implications, such as the use of PSPs as targets, have drawn the attention of researchers and clinicians. To date, the effects of PSP inhibitors are less satisfactory in real-world practice. With breakthroughs in sequencing technologies, scientists can decipher TME investigations via multiomics and higher resolution. These benefits provide an opportunity to explore the TME in a more comprehensive manner and inspire more findings concerning PSPs in the TME. The current review starts by introducing the canonical knowledge of PSPs, including their members, structures and posttranslational modifications for activities. We then summarize the functions of PSPs in regulating cellular homeostasis. In particular, we specified the up-to-date roles of PSPs in modulating the immune microenvironment, adopting hypoxia, reprogramming metabolic processes, and responding to extracellular matrix remodeling. Finally, we introduce preclinical PSP inhibitors with translational value and conclude with clinical trials of PSP inhibitors for cancer treatment.

Quercetin attenuates metastatic ability of human metastatic ovarian cancer cells via modulating multiple signaling molecules involved in cell survival, proliferation, migration and adhesion

Ovarian cancer is the most deadly gynaecology related cancer due to its high metastasizing ability. Quercetin is the most abundant flavonoids received increased interest due to its anti-cancer properties. Although the anticancer property of quercetin is very well known, its anti-metastatic effect on metastatic ovarian cancer cells and their underlying molecular mechanism remains to be elucidated. Quercetin treatment at 50 μM and 75 μM concentration inhibit human metastatic ovarian cancer PA-1 cell survival and proliferation via inactivating PI3k/Akt, Ras/Raf pathways and EGFR expression. It also alters the expression of N-cadherin in PA-1 cells. Quercetin also decreases the secretion of gelatinase enzyme, proteolytic activity of MMP-2/-9, and both MMPs gene expression in metastatic ovarian cancer PA-1 cells. In addition to this quercetin inhibits the migration of PA-1 cells. Treatment of quercetin with PA-1 cells also downregulates the tight junctional molecules such as Claudin-4 and Claudin-11 while upregulates the expression of occludin. It is further validated by cell adhesion assay in which quercetin reduces the adhesion of PA-1 ovarian cancer cells. Results suggest that quercetin inhibits cell survival, proliferation, migration, and adhesion which plays crucial role in ovarian cancer metastasis. Hence, it could be a valuable therapeutic drug for the treatment and prevention of metastatic ovarian cancer.

Resibufogenin inhibits ovarian clear cell carcinoma (OCCC) growth in vivo, and migration of OCCC cells in vitro, by down-regulating the PI3K/AKT and actin cytoskeleton signaling pathways

Patients diagnosed with ovarian clear cell carcinoma (OCCC), a rare histologic subtype of ovarian cancer, often experience poor prognosis owing to the chemoresistance of their disease. Thus, there is an urgent need to identify new therapeutic options for these patients. A drug screen of 172 traditional Chinese herbs identified resibufogenin as a compound that inhibited the growth of cultured OCCC cells. Resibufogenin, a bioactive compound originally isolated from toad venom, is used in traditional Chinese medicine to treat several malignancies. The current study examined the impact of resibufogenin treatment on proliferation, migration, and invasion of ES-2 and TOV-21G OCCC cells in vitro. Flow cytometric analyses were employed to determine if resibufogenin affects apoptosis in OCCC cells. Additionally, the ability of resibufogenin to inhibit tumor growth in vivo was evaluated in murine xenograft models. RNA sequencing, quantitative polymerase chain reactions (qPCR), immunohistochemical assays, and western blotting were used to identify and verify cellular pathways potentially targeted by resibufogenin. Resibufogenin inhibited proliferation, migration, and invasion of OCCC cells, and induced apoptosis in them. Resibufogenin also suppressed the growth of xenograft tumors, which consequently showed lower Ki-67 and higher terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) expression. We observed down-regulation of (a) PI3K and AKT in the PI3K/AKT signaling pathway, and (b) MDM2 and myosin in the actin cytoskeleton pathway upon resibufogenin treatment. Thus, resibufogenin inhibits growth and migration of OCCC cells in vitro and suppresses OCCC growth in vivo through the PI3K/AKT and actin cytoskeleton signaling pathways.

Hypoxia modulates protein phosphatase 2A through HIF-1α dependent and independent mechanisms in human aortic smooth muscle cells and ventricular cardiomyocytes

BACKGROUND AND PURPOSE

Although protein phosphatases regulate multiple cellular functions, their modulation under hypoxia remains unclear. We investigated expression of the protein phosphatase system under normoxic/hypoxic conditions and the mechanism by which hypoxia alters protein phosphatase 2A (PP2A) activity.

EXPERIMENTAL APPROACH

Human cardiovascular cells were cultured in cell type specific media under normoxic or hypoxic conditions (1% O₂ ). Effects on mRNA expression, phosphatase activity, post-translational modification, and involvement of hypoxia inducible factor 1α (HIF-1α) were assessed using RT-PCR, immunoblotting, an activity assay, and siRNA silencing.

KEY RESULTS

All components of the protein phosphatase system studied were expressed in each cell line. Hypoxia attenuated mRNA expression of the transcripts in a cell line- and time-dependent manner. In human aortic smooth muscle cells (HASMC) and AC16 cells, hypoxia decreased PP2Ac activity and mRNA expression without altering PP2Ac abundance. Hypoxia increased demethylated PP2Ac (DPP2Ac) and phosphatase methylesterase 1 (PME-1) abundance but decreased leucine carboxyl methyltransferase 1 (LCMT-1) abundance. HIF-1α siRNA prevented the hypoxia-mediated decrease in phosphatase activity and expression of the catalytic subunit of protein phosphatase 2A (PPP2CA), independently of altering pPP2Ac, DPP2Ac, LCMT-1, or PME-1 abundance.

CONCLUSION AND IMPLICATIONS

Cardiovascular cells express multiple components of the PP2A system. In HASMC and AC16 cells, hypoxia inhibits PP2A activity through HIF-1α-dependent and -independent mechanisms, with the latter being consistent with altered PP2A holoenzyme assembly. This indicates a complex inhibitory effect of hypoxia on the PP2A system, and highlights PP2A as a therapeutic target for diseases associated with dysregulated protein phosphorylation.

Regulation of the phosphoprotein phosphatase 2A system and its modulation during oxidative stress: A potential therapeutic target?

Phosphoprotein phosphatases are of growing interest in the pathophysiology of many diseases and are often the neglected partner of protein kinases. One family member, PP2A, accounts for dephosphorylation of ~55-70% of all serine/threonine phosphosites. Interestingly, dysregulation of kinase signalling is a hallmark of many diseases in which an increase in oxidative stress is also noted. With this in mind, we assess the evidence to support oxidative stress-mediated regulation of the PP2A system In this article, we first present an overview of the PP2A system before providing an analysis of the regulation of PP2A by endogenous inhibitors, post translational modification, and miRNA. Next, a detailed critique of data implicating reactive oxygen species, ischaemia, ischaemia-reperfusion, and hypoxia in regulating the PP2A holoenzyme and associated regulators is presented. Finally, the pharmacological targeting of PP2A, its endogenous inhibitors, and enzymes responsible for its post-translational modification are covered. There is extensive evidence that oxidative stress modulates multiple components of the PP2A system, however, most of the data pertains to the catalytic subunit of PP2A. Irrespective of the underlying aetiology, free radical-mediated attenuation of PP2A activity is an emerging theme. However, in many instances, a dichotomy exists, which requires clarification and mechanistic insight. Nevertheless, this raises the possibility that pharmacological activation of PP2A, either through small molecule activators of PP2A or CIP2A/SET antagonists may be beneficial in modulating the cellular response to oxidative stress. A better understanding of which, will have wide ranging implications for cancer, heart disease and inflammatory conditions.

Dual blockade of PI3K and MEK in combination with radiation in head and neck cancer

Background and purpose

In this study we have combined fractionated radiation treatment (RT) with two molecular targeted agents active against key deregulated signaling pathways in head and neck cancer.

Materials and methods

We used two molecularly characterized, low passage HNSCC cell lines of differing biological characteristics to study the effects of binimetinib and buparlisib in combination with radiation in vitro and in vivo.

Results

Buparlisib was active against both cell lines in vitro whereas binimetinib was more toxic to UT-SCC-14. Neither agent modified radiation sensitivity in vitro. Buparlisib significantly inhibited growth of UT-SSC-15 alone or in combination with RT but was ineffective in UT-SCC-14. Binimetinib did cause a significant delay with RT in UT-SCC-14 and it significantly reduced growth of the UT-SCC-15 tumors both alone and with RT. The tri-modality treatment was not as effective as RT with a single effective agent.

Conclusions

No significant benefit was gained by the combined use of the two agents with RT even though each was efficacious when used alone.

Effects of isoliquiritigenin on ovarian cancer cells

Background

Ovarian cancer is one of the most fatal gynecologic malignancies, with most patients diagnosed at the late stage due to insidious onset and lack of early onset specific symptoms. Previous studies have implied that isoliquiritigenin (ILQ) is a promising chemopreventive agent against oral cancer.

Aim

This study aimed to investigate effects of ILQ and elucidate the related mechanism.

Materials and methods

Ovarian cancer cell lines, SKOV3 and OVCAR3, were treated with various concentrations of ILQ to detect the dose-dependent effects of ILQ and select the suitable concentration. CCK8 assay and clone formation efficiency assays were used to detect viability and proliferation. The cell migration, invasion, and apoptosis were evaluated by wound healing assays, transwell, and flow cytometry assays. The expression of apoptosis-related proteins (Caspase-3, Caspase3-p17, Bcl-2, Bax, and Bim) and related-signaling pathway proteins were also detected by Western blot.

Results

It was observed that the treatment of ILQ inhibited the survival and proliferation of SKOV3 and OVCAR3 cells. ILQ treatment inhibited migration and invasion, and induced apoptosis in SKOV3 and OVCAR3 cells. Also, the ILQ treatment increased the Bax/Bcl-2 ratio in SKOV3 and OVCAR3 cells, suggesting that a mitochondrial apoptotic pathway was triggered. It was also observed that, after treated with ILQ, the phosphorylated form of Akt and mTOR decreased and the expression of GSK3β increased, while P70/S6K decreased. ILQ treatment also decreased the expression of Wnt3a and, therefore, caused the decrease of phosphorylated ERK. ILQ also suppressed the PI3K/Akt/mTOR pathway by reduced the expression level of p-Akt, p-mTOR, P70/S6K and Cyclin D1 in Ishikawa and ES-2 cells.

Conclusion

The data suggested that ILQ inhibited viability, proliferation, and invasion, and induced apoptosis of SKOV3 and OVCAR3 cells through the PI3K/Akt/mTOR pathway. Together, the data revealed that ILQ treatment may be used as a novel strategy for ovarian cancer therapy.

Short hairpin RNA-mediated gene silencing of ADAM17 inhibits the growth of breast cancer MCF‑7 cells in vitro and in vivo and its mechanism of action

A disintegrin and metalloprotease 17 (ADAM17) is highly expressed in many malignant tumors and is closely related to their development. We showed in a previous study that silencing of ADAM17 by siRNA inhibited the growth of MCF-7 breast cancer cells in vitro and in vivo. In the present study, we investigated the effects of ADAM17-short hairpin RNA (ADAM17-shRNA) on MCF-7 breast cancer cells and explored the potential action pathway. In vitro, transfection of shRNAs was performed using a lentivirus, and the effects of ADAM17-shRNA on invasion, proliferation and cell cycle distribution of MCF-7 cells were assessed by Boyden chamber method, real-time cell analysis and flow cytometry, respectively. In vivo, MCF-7 cells with different administrations were transplanted subcutaneously into nude mice, and the effect of ADAM17-shRNA on the growth of transplanted tumors was assessed. In addition, the morphological structures were observed by H&E staining, and the expression of ADAM17 and Ki-67 was assessed by immunohistochemistry; expression of ADAM17, EGFR, p-EGFR, AKT, p-AKT, ERK and p-ERK proteins was assessed by western blotting, respectively. Our data showed that ADAM17-shRNA successfully inhibited ADAM17 mRNA expression, invasion and proliferation of MCF-7 cells resulting in G0/G1 phase arrest, and significantly inhibited the growth of transplanted tumors with larger areas of necrosis, low expression of ADAM17 and Ki-67 and reduced protein expression of ADAM17, EGFR, p-EGFR, AKT, p-AKT, ERK, and p-ERK in the tumor tissues. The present research suggests that ADAM17-shRNA can inhibit MCF-7 cell invasion and proliferation in vitro and inhibit MCF-7 xenograft growth in vivo through the EGFR/PI3K/AKT and EGFR/MEK/ERK signaling pathways.

Augmented O-GlcNAcylation of AMP-activated kinase promotes the proliferation of LoVo cells, a colon cancer cell line

Increasing incidence of various cancers has been reported in diabetic patients. O‐linked N‐acetylglucosamine (O‐GlcNAc) modification of proteins at serine/threonine residues (O‐GlcNAcylation) is an essential post‐translational modification that is upregulated in diabetic patients and has been implicated in tumor growth. However, the mechanisms by which O‐GlcNAcylation promotes tumor growth remain unclear. Given that AMP‐activated kinase (AMPK) has been thought to play important roles in suppressing tumor growth, we evaluated the involvement of AMPK O‐GlcNAcylation on the growth of LoVo cells, a human colon cancer cell line. Results revealed that treatment with Thiamet G (TMG), an inhibitor of O‐GlcNAc hydrolase, increased both anchorage‐dependent and ‐independent growth of the cells. O‐GlcNAc transferase overexpression also increased the growth. These treatments increased AMPK O‐GlcNAcylation in a dose‐dependent manner, which led to reduced AMPK phosphorylation and mTOR activation. Chemical inhibition or activation of AMPK led to increased or decreased growth, respectively, which was consistent with the data with genetic inhibition of AMPK. In addition, TMG‐mediated acceleration of tumor growth was abolished by both chemical and genetic inhibition of AMPK. To examine the effects of AMPK O‐GlcNAcylation in vivo, the LoVo cells were s.c. transplanted onto the backs of BALB/c‐nu/nu mice. Injection of TMG promoted the growth and enhanced O‐GlcNAcylation of the tumors of the mice. Consistent with in vitro data, AMPK O‐GlcNAcylation was increased, which reduced AMPK phosphorylation and resulted in activation of mTOR. Collectively, the higher colon cancer risk of diabetic patients could be due to O‐GlcNAcylation‐mediated AMPK inactivation and subsequent activation of mTOR.

Involvement of Chromatin Remodeling Genes and the Rho GTPases RhoB and CDC42 in Ovarian Clear Cell Carcinoma

Objective

Ovarian clear cell carcinomas (OCCCs) constitute a rare ovarian cancer subtype with distinct clinical features, but may nonetheless be difficult to distinguish morphologically from other subtypes. There is limited knowledge of genetic events driving OCCC tumorigenesis beyond ARID1A, which is reportedly mutated in 30–50% of OCCCs. We aimed to further characterize OCCCs by combined global transcriptional profiling and targeted deep sequencing of a panel of well-established cancer genes. Increased knowledge of OCCC-specific genetic aberrations may help in guiding development of targeted treatments and ultimately improve patient outcome.

Methods

Gene expression profiling of formalin-fixed, paraffin-embedded (FFPE) tissue from a cohort of the major ovarian cancer subtypes (cohort 1; n = 67) was performed using whole-genome cDNA-mediated Annealing, Selection, extension and Ligation (WG-DASL) bead arrays, followed by pathway, gene module score, and gene ontology analyses, respectively. A second FFPE cohort of 10 primary OCCCs was analyzed by targeted DNA sequencing of a panel of 60 cancer-related genes (cohort 2). Non-synonymous and non-sense variants affecting single-nucleotide variations and insertions or deletions were further analyzed. A tissue microarray of 43 OCCCs (cohort 3) was used for validation by immunohistochemistry and chromogenic in situ hybridization.

Results

Gene expression analyses revealed a distinct OCCC profile compared to other histological subtypes, with, e.g., ERBB2, TFAP2A, and genes related to cytoskeletal actin regulation being overexpressed in OCCC. ERBB2 was, however, not overexpressed on the protein level and ERBB2 amplification was rare in the validation cohort. Targeted deep sequencing revealed non-synonymous variants or insertions/deletions in 11/60 cancer-related genes. Genes involved in chromatin remodeling, including ARID1A, SPOP, and KMT2D were frequently mutated across OCCC tumors.

Conclusion

OCCCs appear genetically heterogeneous, but harbor frequent alterations in chromatin remodeling genes. Overexpression of TFAP2A and ERBB2 was observed on the mRNA level in relation to other ovarian cancer subtypes. However, overexpression of ERBB2 was not reflected by HER2 amplification or protein overexpression in the OCCC validation cohort. In addition, Rho GTPase-dependent actin organization may also play a role in OCCC pathogenesis and warrants further investigation. The distinct biological features of OCCC discovered here may provide a basis for novel targeted treatment strategies.

"Combo" nanomedicine: Co-delivery of multi-modal therapeutics for efficient, targeted, and safe cancer therapy

The dynamic and versatile nature of diseases such as cancer has been a pivotal challenge for developing efficient and safe therapies. Cancer treatments using a single therapeutic agent often result in limited clinical outcomes due to tumor heterogeneity and drug resistance. Combination therapies using multiple therapeutic modalities can synergistically elevate anti-cancer activity while lowering doses of each agent, hence, reducing side effects. Co-administration of multiple therapeutic agents requires a delivery platform that can normalize pharmacokinetics and pharmacodynamics of the agents, prolong circulation, selectively accumulate, specifically bind to the target, and enable controlled release in target site. Nanomaterials, such as polymeric nanoparticles, gold nanoparticles/cages/shells, and carbon nanomaterials, have the desired properties, and they can mediate therapeutic effects different from those generated by small molecule drugs (e.g., gene therapy, photothermal therapy, photodynamic therapy, and radiotherapy). This review aims to provide an overview of developing multi-modal therapies using nanomaterials ("combo" nanomedicine) along with the rationale, up-to-date progress, further considerations, and the crucial roles of interdisciplinary approaches.