Mutant p53 Amplifies Epidermal Growth Factor Receptor Family Signaling to Promote Mammary Tumorigenesis

Case series of Li-Fraumeni syndrome: carcinogenic mechanisms in breast cancer with TP53 pathogenic variant carriers

BACKGROUND

Li-Fraumeni syndrome (LFS), a hereditary condition attributed to TP53 pathogenic variants,(PV), is associated with high risks for various malignant tumors, including breast cancer. Notably, individuals harboring TP53 PVs are more likely (67-83%) to develop HER2 + breast cancer than noncarriers (16-25%). In this retrospective study, we evaluated the associations between TP53 variants and breast cancer phenotype.

METHODS

We conducted a retrospective review of the medical records of patients with LFS treated at a single institution and reviewed the literature on TP53 functions and the mechanisms underlying HER2 + breast cancer development in LFS.

RESULTS

We analyzed data for 10 patients with LFS from 8 families. The median age at the onset of the first tumor was 35.5 years. Only case 2 met the classic criteria; this patient harbored a nonsense variant, whereas the other patients carried missense variants. We observed that 9 of 10 patients developed breast cancer. Immunohistochemical analyses revealed that 40% of breast cancers in patients with LFS were HR - /HER2 + . The median age at the onset of breast cancer was slightly younger in HR - /HER2 + tumors than in HR + /HER2 -  tumors (31 years and 35.5 years, respectively).

CONCLUSIONS

The occurrence of HER2 + breast cancer subtype was 40% in our LFS case series, which is greater than that in the general population (16-25%). Some TP53 PVs may facilitate HER2-derived oncogenesis in breast cancer. However, further studies with larger sample sizes are warranted to clarify the oncogenic mechanisms underlying each subtype of breast cancer in TP53 PV carriers.

Is loss of p53 a driver of ductal carcinoma in situ progression?

Ductal carcinoma in situ (DCIS) is a non-obligate precursor of invasive carcinoma. Multiple studies have shown that DCIS lesions typically possess a driver mutation associated with cancer development. Mutation in the TP53 tumour suppressor gene is present in 15-30% of pure DCIS lesions and in ~30% of invasive breast cancers. Mutations in TP53 are significantly associated with high-grade DCIS, the most likely form of DCIS to progress to invasive carcinoma. In this review, we summarise published evidence on the prevalence of mutant TP53 in DCIS (including all DCIS subtypes), discuss the availability of mouse models for the study of DCIS and highlight the need for functional studies of the role of TP53 in the development of DCIS and progression from DCIS to invasive disease.

Clustering subtypes of breast cancer by combining immunohistochemistry profiles and metabolism characteristics measured using FDG PET/CT

BACKGROUND

The aim of this study was to investigate the effect of combining immunohistochemical profiles and metabolic information to characterize breast cancer subtypes.

METHODS

This retrospective study included 289 breast tumors from 284 patients who underwent preoperative 18 F-fluorodeoxyglucose (FDG) positron emission tomography/ computed tomography (PET/CT). Molecular subtypes of breast cancer were classified as Hormonal, HER2, Dual (a combination of both Hormonal and HER2 features), and triple-negative (TN). Histopathologic findings and immunohistochemical results for Ki-67, EGFR, CK 5/6, and p53 were also analyzed. The maximum standardized uptake value (SUV) measured from FDG PET/CT was used to evaluate tumoral glucose metabolism.

RESULTS

Overall, 182, 24, 47, and 36 tumors were classified as Hormonal, HER2, Dual, and TN subtypes, respectively. Molecular profiles of tumor aggressiveness and the tumor SUV revealed a gradual increase from the Hormonal to the TN type. The tumor SUV was significantly correlated with tumor size, expression levels of p53, Ki-67, and EGFR, and nuclear grade (all p < 0.001). In contrast, the tumor SUV was negatively correlated with the expression of estrogen receptors (r = - 0.234, p < 0.001) and progesterone receptors (r = - 0.220, p < 0.001). Multiple linear regression analysis revealed that histopathologic markers explained tumor glucose metabolism (adjusted R-squared value 0.238, p < 0.001). Tumor metabolism can thus help define breast cancer subtypes with aggressive/adverse prognostic features.

CONCLUSIONS

Metabolic activity measured using FDG PET/CT was significantly correlated with the molecular alteration profiles of breast cancer assessed using immunohistochemical analysis. Combining molecular markers and metabolic information may aid in the recognition and understanding of tumor aggressiveness in breast cancer and be helpful as a prognostic marker.

Gain-of-Function Mutant TP53 R248Q Overexpressed in Epithelial Ovarian Carcinoma Alters AKT-Dependent Regulation of Intercellular Trafficking in Responses to EGFR/MDM2 Inhibitor

As the most common gene mutation found in cancers, p53 mutations are detected in up to 96% of high-grade serous ovarian carcinoma (HGSOC). Meanwhile, mutant p53 overexpression is known to drive oncogenic phenotypes in cancer patients and to sustain the activation of EGFR signaling. Previously, we have demonstrated that the combined inhibition of EGFR and MDM2-p53 pathways, by gefitinib and JNJ-26854165, exerts a strong synergistic lethal effect on HGSOC cells. In this study, we investigated whether the gain-of-function p53 mutation (p53^R248Q) overexpression could affect EGFR-related signaling and the corresponding drug inhibition outcome in HGSOC. The targeted inhibition responses of gefitinib and JNJ-26854165, in p53^R248Q-overexpressing cells, were extensively evaluated. We found that the phosphorylation of AKT increased when p53^R248Q was transiently overexpressed. Immunocytochemistry analysis further showed that upon p53^R248Q overexpression, several AKT-related regulatory proteins translocated in unique intracellular patterns. Subsequent analysis revealed that, under the combined inhibition of gefitinib and JNJ-26854165, the cytonuclear trafficking of EGFR and MDM2 was disrupted. Next, we analyzed the gefitinib and JNJ-26854165 responses and found differential sensitivity to the single- or combined-drug inhibitions in p53^R248Q-overexpressing cells. Our findings suggested that the R248Q mutation of p53 in HGSOC caused significant changes in signaling protein function and trafficking, under EGFR/MDM2-targeted inhibition. Such knowledge could help to advance our understanding of the role of mutant p53 in ovarian carcinoma and to improve the prognosis of patients receiving EGFR/MDM2-targeted therapies.

Mutant p53 drives the loss of heterozygosity by the upregulation of Nek2 in breast cancer cells

BACKGROUND

Mutations in one allele of the TP53 gene in early stages are frequently followed by the loss of the remaining wild-type p53 (wtp53) allele (p53LOH) during tumor progression. Despite the strong notion of p53LOH as a critical step in tumor progression, its oncogenic outcomes that facilitate the selective pressure for p53LOH occurrence were not elucidated.

METHODS

Using MMTV;ErbB2 mouse model of breast cancer carrying heterozygous R172H p53 mutation, we identified a novel gain-of-function (GOF) activity of mutant p53 (mutp53): the exacerbated loss of wtp53 allele in response to γ-irradiation.

RESULTS

As consequences of p53LOH in mutp53 heterozygous cells, we observed profound stabilization of mutp53 protein, the loss of p21 expression, the abrogation of G2/M checkpoint, chromosomal instability, centrosome amplification, and transcriptional upregulation of mitotic kinase Nek2 (a member of Never in Mitosis (NIMA) Kinases family) involved in the regulation of centrosome function. To avoid the mitotic catastrophe in the absence of G2/M checkpoint, cells with centrosome amplification adapt Nek2-mediated centrosomes clustering as pro-survival mutp53 GOF mechanism enabling unrestricted proliferation and clonal expansion of cells with p53LOH. Thus, the clonal dominance of mutp53 cells with p53LOH may represent the mechanism of irradiation-induced p53LOH. We show that pharmacological and genetic ablation of Nek2 decreases centrosome clustering and viability of specifically mutp53 cells with p53LOH.

CONCLUSION

In a heterogeneous tumor population, Nek2 inhibition may alter the selective pressure for p53LOH by contraction of the mutp53 population with p53LOH, thus, preventing the outgrowth of genetically unstable, more aggressive cells.

Attenuation of p53 mutant as an approach for treatment Her2-positive cancer

Breast cancer is one of the world's leading causes of oncological disease-related death. It is characterized by a high degree of heterogeneity on the clinical, morphological, and molecular levels. Based on molecular profiling breast carcinomas are divided into several subtypes depending on the expression of a number of cell surface receptors, e.g., ER, PR, and HER2. The Her2-positive subtype occurs in ~10-15% of all cases of breast cancer, and is characterized by a worse prognosis of patient survival. This is due to a high and early relapse rate, as well as an increased level of metastases. Several FDA-approved drugs for the treatment of Her2-positive tumors have been developed, although eventually cancer cells develop drug resistance. These drugs target either the homo- or heterodimerization of Her2 receptors or the receptors' RTK activity, both of them being critical for the proliferation of cancer cells. Notably, Her2-positive cancers also frequently harbor mutations in the TP53 tumor suppressor gene, which exacerbates the unfavorable prognosis. In this review, we describe the molecular mechanisms of RTK-specific drugs and discuss new perspectives of combinatorial treatment of Her2-positive cancers through inhibition of the mutant form of p53.

Targeting DNA and mutant p53 by a naphthalimide derivative, NA20, exhibits selective inhibition in gastric tumorigenesis by blocking mutant p53-EGFR signaling pathway

Mutations of p53 in cancer cells not only subvert its antiproliferative properties but can also promote various oncogenic responses through a gain-of-function activity. Pharmacological manipulation of the mutant p53 pathway by specific compounds could be an effective strategy for cancer therapy. We show here that gain-of-function p53 mutation in gastric cancer cells promotes tumorigenesis by enhancing p53-EGFR (epidermal growth factor receptor) signaling pathway, and such process can be blocked by small molecule NA20, a naphthalimide derivative that exhibited selective inhibition in p53 mutant gastric cancer cell lines. We found that targeting DNA and blocking the mutant p53-drived carcinogenicity accounted for the primary antitumor effect of NA20 in gastric tumor models. NA20 bound to DNA and p53 identified by a combination of drug tracking, DNA relaxation assay and coimmunoprecipitation-mass spectrometry (CoIP-MS) detection, which led to the p21 activation and the suppression of EGFR signal cascading, thereby evoking cell cycle arrest and cell apoptosis, finally leading to cancer cell inhibition both in vitro and in vivo. Taken together, these results suggest that NA20 may be a potential candidate for gastric cancer therapy.

Pterostilbene as a Phytochemical Compound Induces Signaling Pathways Involved in the Apoptosis and Death of Mutant P53-Breast Cancer Cell Lines

Pterostilbene is a natural nonflavonoid polyphenolic compound. It shows a remarkable range of biological activities, including antiproliferative, antiinflammatory, and antioxidant activity. However, the mechanism of action of PT in breast cancer cells containing mutant p53 protein has not been fully elucidated. Therefore, the present study was aimed at investigating the influence of PT on signaling pathways involved in the apoptosis of mutant p53-breast cancer cell lines. Immunocytochemistry and Western Immunoblotting techniques were used in this study. The present data showed that the viabilities and the proliferations of MDA-MB-231 and T-47D decreased significantly (P < 0.001) after treatment with different concentrations of PT. In addition, the morphological characteristics of both cell lines were changed after treatment with PT. Decreased protein expression of mutant p53 (R280 K, L194F) in MDA-MB-231 and T-47D breast cancer cell lines has also been achieved. In addition, overexpression of pro-apoptotic (Bax) protein, caspase-3 activity and histone release were increased after treatment of both cell lines with different PT concentrations. Furthermore, the protein expressions of cyclin D1, mTOR, and oncogenic β-catenin were significantly downregulated after treatment of both cell lines with PT. In conclusion, downregulations of protein expression of mutant p53, cyclin D1, mTOR, and β-catenin were increased after both cell lines had been treated with pterostilbene. PT could point to a promising use against the development and the progression of breast cancer as a natural therapeutic agent.

p53 balances between tissue hierarchy and anarchy

Normal tissues are organized in a hierarchical model, whereas at the apex of these hierarchies reside stem cells (SCs) capable of self-renewal and of producing differentiated cellular progenies, leading to normal development and homeostasis. Alike, tumors are organized in a hierarchical manner, with cancer SCs residing at the apex, contributing to the development and nourishment of tumors. p53, the well-known ‘guardian of the genome’, possesses various roles in embryonic development as well as in adult SC life and serves as the ‘guardian of tissue hierarchy’. Moreover, p53 serves as a barrier for dedifferentiation and reprogramming by constraining the cells to a somatic state and preventing their conversion to SCs. On the contrary, the mutant forms of p53 that lost their tumor suppressor activity and gain oncogenic functions serve as ‘inducers of tissue anarchy’ and promote cancer development. In this review, we discuss these two sides of the p53 token that sentence a tissue either to an ordered hierarchy and life or to anarchy and death. A better understanding of these processes may open new horizons for the development of new cancer therapies.

Loss of TRP53 (p53) accelerates tumorigenesis and changes the tumor spectrum of SJL/J mice

Known as the guardian of the genome, transformation-related protein 53 (TRP53) is a well -known tumor suppressor. Here, we describe a novel TRP53 deficient mouse model on a tumor prone background—SJL/J mice. The absence of TRP53 (TRP53 nullizygosity) leads to a shift in the tumor spectrum from a non-Hodgkin’s-like disease to thymic lymphomas and testicular teratomas at a very rapid tumor onset averaging ~12 weeks of age. In haplotype studies, comparing tumor prone versus tumor resistant Trp53 null mouse strains, we found that other tumor suppressor, DNA repair and/or immune system genes modulate tumor incidence in TRP53 null strains, suggesting that even a strong tumor suppressor such as TRP53 is modulated by genetic background. Due to their rapid development of tumors, the SJL/J TRP53 null mice generated here can be used as an efficient chemotherapy or immunotherapy screening mouse model.

Irradiation induces p53 loss of heterozygosity in breast cancer expressing mutant p53

Mutations in one allele of the TP53 gene in cancer early stages are frequently followed by the loss of the remaining wild-type allele (LOH) during tumor progression. However, the clinical impact of TP53 mutations and p53LOH, especially in the context of genotoxic modalities, remains unclear. Using MMTV;ErbB2 model carrying a heterozygous R172H p53 mutation, we report a previously unidentified oncogenic activity of mutant p53 (mutp53): the exacerbation of p53LOH after irradiation. We show that wild-type p53 allele is partially transcriptionally competent and enables the maintenance of the genomic integrity under normal conditions in mutp53 heterozygous cells. In heterozygous cells γ-irradiation promotes mutp53 stabilization, which suppresses DNA repair and the cell cycle checkpoint allowing cell cycle progression in the presence of inefficiently repaired DNA, consequently increases genomic instability leading to p53LOH. Hence, in mutp53 heterozygous cells, irradiation facilitates the selective pressure for p53LOH that enhances cancer cell fitness and provides the genetic plasticity for acquiring metastatic properties.

Wild type- and mutant p53 proteins in mitochondrial dysfunction: emerging insights in cancer disease

Deregulated cell metabolism is one of the cancer hallmarks. Mitochondrial DNA mutations and enzyme defects, aberrant tumor suppressor or oncogenic activities cause mitochondrial dysfunction leading to deregulated cellular energetics. The tumor suppressor protein, p53 is a tetrameric transcription factor that in response to diverse genotoxic and non-genotoxic insults activates a plethora of target genes to preserve genome integrity. In the last two decades the discovery of cytoplasmic p53 localization focused intense research on its extra-nuclear functions. The ability of p53 to induce apoptosis acting directly at mitochondria and the related mechanisms of p53 localization and translocation in the cytoplasm have been investigated. A role of cytoplasmic p53 in autophagy, pentose phosphate pathway, fatty acid synthesis and oxidation, and drug response has been proposed. TP53 gene is mutated in more than half of human cancers. In parallel to loss of tumor suppressive functions, mutant p53 proteins often gain new tumorigenic activities (GOF, gain of function). It has been recently shown that mutant p53 proteins mediate metabolic changes thereby promoting cancer development and metastases. Here we review the contribution of either wild-type p53 or mutant p53 proteins to the fine-tuning of mitochondrial metabolism of both normal and cancer cells. Greater knowledge at the mechanistic level might provide insights to develop new cancer therapeutic approaches.

Prevalence of Her3 in gastric cancer and its association with molecular prognostic markers: a Saudi cohort based study

Her 3 is a member of epidermal growth factor receptors. Mutated, oncogenic Her3 is reported in gastric and colonic cancers with emerging evidence that Her3 can be a potential target for molecular therapies. There is a paucity of studies regarding Her3 and its prognostic implications in gastric cancer in our region. In this study, we evaluated prevalence of Her3 in gastric cancer, in a Saudi cohort of cases, along with its association with prognostic markers p53 and Ki-67. The study was conducted in Department of Pathology of King Fahd Hospital of Imam Abdulrahman Bin Faisal University, Dammam, KSA. Fifty cases of gastric carcinoma were selected from the pathology files that fulfilled the inclusion criteria. Clinico-pathological parameters, Laurens histological classification, and immunohistochemical staining for Her3, p53, and Ki-67 were done. Her 3 positive cases were also evaluated for Her-2neu co-expression. Her3 positivity was seen in 16% (n = 8) out of a total of 50 cases. The median age of presentation was 44 years. Within Her3 positive cases, a female preponderance of 63% (n = 5), presence of high grade tumors in 75% (n = 6), diffuse gastric carcinoma in 63% (n = 5), diffuse to focal p53 positivity in 63% (n = 5), and a high to moderate Ki-67 proliferation index in 75% (n = 6) of cases was seen. Her3 expression was independent of Her-2neu status. Her3 prevalence of 16% with a median age of 44 years at presentation was less than in other reported studies, highlighting the concept of ethnic and regional variation in tumor characteristics. Her3 association with diffuse gastric carcinoma, high grade tumors, diffuse to focal p53 positivity and high to moderate Ki-67 proliferation index points towards a more aggressive clinical behavior.

Synergistic antitumour activity of HDAC inhibitor SAHA and EGFR inhibitor gefitinib in head and neck cancer: a key role for ΔNp63α

BACKGROUND

Epidermal growth factor receptor (EGFR) overexpression is associated with the development of head and neck cancer (HNC) and represents one of the main therapeutic targets for this disease. The use of EGFR inhibitors has limited efficacy due to their primary and acquired resistance, partially because of increased epithelial to mesenchymal transition (EMT). The HDAC inhibitor SAHA has been shown to revert EMT in different tumours, including HNC. In this study, we investigated the cooperative role of SAHA and the EGFR tyrosine kinase inhibitor gefitinib in both HPV-positive and HPV-negative HNC cell lines.

METHODS

A panel of 12 HPV-positive and HPV-negative HNC cell lines were screened for cell viability upon treatment with SAHA, gefitinib and the combination of the two. Epithelial/mesenchymal marker expression, as well as activation of signalling pathway, were assessed upon SAHA treatment. ΔNp63α silencing with shRNA lentiviral particles was used to determine its role in cell proliferation, migration and TGFβ pathway activation.

RESULTS

We found that both SAHA and gefitinib have antitumour activity in both HPV-positive and HPV-negative HNC cell lines and that their combination has a synergistic effect in inhibiting cell growth. SAHA treatment reverts EMT and inhibits the expression of the transcription factor ΔNp63α. Suppression of ΔNp63α reduces EGFR protein levels and decreases cell proliferation and TGFβ-dependent migration in both HPV-positive and HPV-negative HNC cell lines.

CONCLUSIONS

Our results, by giving a clear molecular mechanism at the basis of the antitumour activity of SAHA in HNC cell lines, provide a rationale for the clinical evaluation of SAHA in combination with gefitinib in both HPV-positive and HPV-negative HNC patients. Further knowledge is key to devising additional lines of combinatorial treatment strategies for this disease.

Regulators of Oncogenic Mutant TP53 Gain of Function

The tumor suppressor p53 (TP53) is the most frequently mutated human gene. Mutations in TP53 not only disrupt its tumor suppressor function, but also endow oncogenic gain-of-function (GOF) activities in a manner independent of wild-type TP53 (wtp53). Mutant TP53 (mutp53) GOF is mainly mediated by its binding with other tumor suppressive or oncogenic proteins. Increasing evidence indicates that stabilization of mutp53 is crucial for its GOF activity. However, little is known about factors that alter mutp53 stability and its oncogenic GOF activities. In this review article, we primarily summarize key regulators of mutp53 stability/activities, including genotoxic stress, post-translational modifications, ubiquitin ligases, and molecular chaperones, as well as a single nucleotide polymorphism (SNP) and dimer-forming mutations in mutp53.

Molecular Mechanisms Governing the Stem Cell's Fate in Brain Cancer: Factors of Stemness and Quiescence

Cellular quiescence is a reversible, non-cycling state controlled by epigenetic, transcriptional and niche-associated molecular factors. Quiescence is a condition where molecular signaling pathways maintain the poised cell-cycle state whilst enabling rapid cell cycle re-entry. To achieve therapeutic breakthroughs in oncology it is crucial to decipher these molecular mechanisms employed by the cancerous milieu to control, maintain and gear stem cells towards re-activation. Cancer stem-like cells (CSCs) have been extensively studied in most malignancies, including glioma. Here, the aberrant niche activities skew the quiescence/activation equilibrium, leading to rapid tumor relapse after surgery and/or chemotherapy. Unraveling quiescence mechanisms promises to afford prevention of (often multiple) relapses, a key problem in current glioma treatment. This review article covers the current knowledge regarding normal and aberrant cellular quiescence control whilst also exploring how different molecular mechanisms and properties of the neighboring cells can influence the molecular processes behind glioma stem cell quiescence.

Mutant p53 gain of function induces HER2 over-expression in cancer cells

Background

HER2 over-expression is related with a poor prognosis in patients with invasive breast cancer tumors. Clinical associations have reported that somatic mutations of p53 more frequently detected in cases of sporadic breast cancer of the HER2 subtypes, besides a high percentage of HER2-amplifying tumors carry germline mutations of p53. The mechanisms responsible for the acquisition of oncogenic functions of p53 mutant proteins (mtp53), known as Gain of Function (GOF), over HER2 expression have not been reported. The objective of this study was to evaluate a possible relationship between p53 mutants and HER2 regulation.

Methods

HER2 expression (transcription and protein), as well as HER2 protein stabilization have been evaluated after inducing or silencing of p53 mutants’ expression in cell lines. Finally, we evaluated the interaction of the p53 mutants over the HER2 receptor promoter.

Results

Higher HER2 expression in cell lines harboring endogenous mtp53 compared with wt or null expression of p53 cell lines. Transfection of p53 mutants (R248Q and R273C) in cell lines increased the expression of HER2. Silencing of p53 mutants, decrease HER2 expression. The p53 mutants R248Q and R273C significantly increase the luciferase activity on the HER2 promoter, and both mutants also promote acetylation of H3 and H4 histones binding in it.

Conclusions

These findings show for the first time that p53 mutants induce over-expression of HER2 at transcriptional level of the HER2 protein. Our results could have clinical implications in breast cancer and other types of cancer where HER2 is over-expressed and used as a therapy target.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4613-1) contains supplementary material, which is available to authorized users.

Heat shock factor 1 confers resistance to lapatinib in ERBB2-positive breast cancer cells

Despite success of ERBB2-targeted therapies such as lapatinib, resistance remains a major clinical concern. Multiple compensatory receptor tyrosine kinase (RTK) pathways are known to contribute to lapatinib resistance. The heterogeneity of these adaptive responses is a significant hurdle for finding most effective combinatorial treatments. The goal of this study was to identify a unifying molecular mechanism whose targeting could help prevent and/or overcome lapatinib resistance. Using the MMTV-ERBB2;mutant p53 (R175H) in vivo mouse model of ERBB2-positive breast cancer, together with mouse and human cell lines, we compared lapatinib-resistant vs. lapatinib-sensitive tumor cells biochemically and by kinome arrays and evaluated their viability in response to a variety of compounds affecting heat shock response. We found that multiple adaptive RTKs are activated in lapatinib-resistant cells in vivo, some of which have been previously described (Axl, MET) and some were novel (PDGFRα, PDGFRβ, VEGFR1, MUSK, NFGR). Strikingly, all lapatinib-resistant cells show chronically activated HSF1 and its transcriptional targets, heat shock proteins (HSPs), and, as a result, superior tolerance to proteotoxic stress. Importantly, lapatinib-resistant tumors and cells retained sensitivity to Hsp90 and HSF1 inhibitors, both in vitro and in vivo, thus providing a unifying and actionable therapeutic node. Indeed, HSF1 inhibition simultaneously downregulated ERBB2, adaptive RTKs and mutant p53, and its combination with lapatinib prevented development of lapatinib resistance in vitro. Thus, the kinome adaptation in lapatinib-resistant ERBB2-positive breast cancer cells is governed, at least in part, by HSF1-mediated heat shock pathway, providing a novel potential intervention strategy to combat resistance.

p53 and metabolism: from mechanism to therapeutics

The tumor cell changes itself and its microenvironment to adapt to different situations, including action of drugs and other agents targeting tumor control. Therefore, metabolism plays an important role in the activation of survival mechanisms to keep the cell proliferative potential. The Warburg effect directs the cellular metabolism towards an aerobic glycolytic pathway, despite the fact that it generates less adenosine triphosphate than oxidative phosphorylation; because it creates the building blocks necessary for cell proliferation. The transcription factor p53 is the master tumor suppressor; it binds to more than 4,000 sites in the genome and regulates the expression of more than 500 genes. Among these genes are important regulators of metabolism, affecting glucose, lipids and amino acids metabolism, oxidative phosphorylation, reactive oxygen species (ROS) generation and growth factors signaling. Wild-type and mutant p53 may have opposing effects in the expression of these metabolic genes. Therefore, depending on the p53 status of the cell, drugs that target metabolism may have different outcomes and metabolism may modulate drug resistance. Conversely, induction of p53 expression may regulate differently the tumor cell metabolism, inducing senescence, autophagy and apoptosis, which are dependent on the regulation of the PI3K/AKT/mTOR pathway and/or ROS induction. The interplay between p53 and metabolism is essential in the decision of cell fate and for cancer therapeutics.

Genomic Profiling on an Unselected Solid Tumor Population Reveals a Highly Mutated Wnt/β-Catenin Pathway Associated with Oncogenic EGFR Mutations

Oncogenic epidermal growth factor receptors (EGFRs) can recruit key effectors in diverse cellular processes to propagate oncogenic signals. Targeted and combinational therapeutic strategies have been successfully applied for treating EGFR-driven cancers. However, a main challenge in EGFR therapies is drug resistance due to mutations, oncogenic shift, alternative signaling, and other potential mechanisms. To further understand the genetic alterations associated with oncogenic EGFRs and to provide further insight into optimal and personalized therapeutic strategies, we applied a proprietary comprehensive next-generation sequencing (NGS)-based assay of 435 genes to systematically study the genomic profiles of 1565 unselected solid cancer patient samples. We found that activating EGFR mutations were predominantly detected in lung cancer, particularly in non-small cell lung cancer (NSCLC). The mutational landscape of EGFR-driven tumors covered most key signaling pathways and biological processes. Strikingly, the Wnt/β-catenin pathway was highly mutated (48 variants detected in 46% of the EGFR-driven tumors), and its variant number topped that in the TP53/apoptosis and PI3K-AKT-mTOR pathways. Furthermore, an analysis of mutation distribution revealed a differential association pattern of gene mutations between EGFR exon 19del and EGFR L858R. Our results confirm the aggressive nature of the oncogenic EGFR-driven tumors and reassure that a combinational strategy should have advantages over an EGFR-targeted monotherapy and holds great promise for overcoming drug resistance.

NEDD4 over-expression regulates the afatinib resistant phenotype of NSCLC cells

We focused on defining the role of the E3 ligase NEDD4 in NSCLC cell afatinib resistance. Afatinib resistant H1975 clones over-expressed NEDD4 and c-MET compared to control clones and expressed less ERBB1, ERBB3, ERBB4 and PTEN than control clones. Knock down of NEDD4 enhanced the expression of PTEN, ERBB1/3/4 and c-MET. This was also associated with a ∼3-fold enhancement in both mTOR expression and mTOR phosphorylation and a ∼4-fold elevation in phospho-ULK-1 S757 levels. In the absence of NEDD4 or the autophagy regulatory protein Beclin1, neither the drug combination of [pemetrexed + sildenafil] nor the HDAC inhibitor sodium valproate was as capable of: reducing the expression of ERBB1/3/4; reducing phosphorylation of ULK-1 S757; or at enhancing the phosphorylation of ULK-1 S317 and ATG13 S318. [Pemetrexed + sildenafil] exposure, via autophagic degradation, reduced the expression of multiple HDACs. Reduced expression of Class I HDACs lowered the expression of ERBB1/3/4 and PTEN. Treatment of afatinib resistant clones lacking NEDD4 with [pemetrexed + sildenafil] or sodium valproate resulted in a weaker induction of autophagosome and autolysosome formation and with reduced cell killing. Knock down of NEDD4 reduced [pemetrexed + sildenafil] lethality; knock down of PTEN enhanced drug-induced killing. Combined knock down of NEDD4 and PTEN reduced the elevated amount of killing caused by PTEN knock down alone back to basal levels. Collectively, our data argue that NEDD4 plays an essential role in maintaining the afatinib-resistant phenotype in our resistant H1975 clones.

ErbB2 inhibition by lapatinib promotes degradation of mutant p53 protein in cancer cells

Mutations in the p53 tumor suppressor gene are the most prevalent genetic events in human Her2-positive breast cancer and are associated with poor prognosis and survival. Human clinical data and our in vitro and in vivo studies strongly suggest potent oncogenic cooperation between mutant p53 and Her2 (ErbB2). Yet, the translational significance of mutant p53 in Her2 positive breast cancer, especially with respect to Her2-targeted therapies, has not been evaluated. Our previous work identified novel oncogenic activity of mutant p53 whereby mutp53 amplifies ErbB2 signaling via the mutp53-HSF1-ErbB2 feed-forward loop. Here we report that pharmacological interception of this circuit by ErbB2 inhibitor lapatinib downregulates mutant p53 in vitro and in vivo. We found that ErbB2 inhibition by lapatinib inhibits transcription factor HSF1, and its target Hsp90, followed by mutant p53 degradation in MDM2 dependent manner. Thus, our data suggest that mutant p53 sensitizes cancer cells to lapatinib via two complementary mechanisms: mutant p53 mediated amplification of ErbB2 signaling, and simultaneous annihilation of both potent oncogenic drivers, ErbB2 and mutant p53. Hence, our study could provide valuable information for the optimization of therapeutic protocols to achieve superior clinical effects in the treatment of Her2 positive breast cancer.

Total flavonoid aglycones extract in Radix scutellariae inhibits lung carcinoma and lung metastasis by affecting cell cycle and DNA synthesis

ETHNOPHARMACOLOGICAL RELEVANCE

Radix Scutellariae (Scutellaria baicalensis Georgi, RS), a traditional herbal medicine commonly used to treat inflammation, hypertension, cardiovascular disease, bacterial and viral infections, is reported to treat lung cancer by supplements of modern medicine. The total flavonoid aglycones extract (TFAE) from RS is the most important composition for the pharmacodynamic effects. The present study was designed to evaluate the anti-lung tumor effect of TFAE on A549 cells and A549 cell nude mice xenografts. The aim of the study is to investigate the effect and mechanism of TFAE treating non-small cell lung cancer both in vitro and in vivo.

MATERIALS AND METHODS

The anti-tumor activity of TFAE in vitro was investigated using the MTT assay. The changes of cell invasion and migration were detected by Transwell assay and tube formation experiments were used to detect the anti-angiogenic effect. The anti-tumor effects of TFAE in vivo were evaluated in A549 cell nude mice xenografts. The mechanism of TFAE was detected by flow cytometry technology, western blot assay and immuno-histochemistry assay.

RESULTS

In vitro, TFAE inhibited the proliferation, invasion and migration of A549 cells in a dose- and time-dependent manner. In vivo, TFAE by oral administration at 100mg/kg for 30 days decreased the tumor volume and tumor weight in A549 cell xenograft by 25.5% with no statistical significance (P<0.05) compared to the cis-platinum positive control group (30.0%). The cell cycle and DNA synthesis experiment illustrated that TFAE could induce A549 cell cycle to arreste in S phase and DNA synthesis in A549 cells be inhibited, while TFAE had no influence on apoptosis of A549 cells. Western Blot assay demonstrated that the treatment of TFAE could make Cyclin D1 decrease and p53 increase both in vitro and in vivo.

CONCLUSION

TFAE displayed the inhibition effects of non-small cell lung cancer both in vitro and in vivo and the underlying mechanism might be related to the increased p53 protein expression and decreased Cyclin D1 expression, leading to cell cycle arrested in S phase and the decrease of DNA synthesis.

Mutant p53 and mTOR/PKM2 regulation in cancer cells

Mutations of TP53 gene are the most common feature in aggressive malignant cells. In addition to the loss of the tumor suppressive role of wild-type p53, hotspot mutant p53 isoforms display oncogenic proprieties notoriously referred as gain of functions (GOFs) which result in chemoresistance to therapies, genomic instability, aberrant deregulation of cell cycle progression, invasiveness and enhanced metastatic potential, and finally, in patient poor survival rate. The identification of novel functional oncogenic pathways regulated by mutant p53 represent and intriguing topic for emerging therapies against a broad spectrum of cancer types bearing mutant TP53 gene. Mammalian target of rapamycin (mTOR), as well as pyruvate kinase isoform M2 (PKM2) are master regulators of cancer growth, metabolism, and cell proliferation. Herein, we report that GOF mutant R175H and R273H p53 proteins trigger PKM2 phosphorylation on Tyr 105 through the involvement of mTOR signaling. Our data, together with the newly discovered connection between mutant p53 and mTOR stimulation, raise important implications for the potential therapeutic use of synthetic drugs inhibiting mTOR/PKM2 axis in cancer cells bearing mutant TP53 gene. We further hypothesize that mTOR/PKM2 pathway stimulation serves to sustain the oncogenic activity of mutant p53 through both the enhancement of chemoresistance and of aerobic glycolysis of cancer cells. © 2016 IUBMB Life, 68(9):722-726, 2016.

Mutant p53 - Heat Shock Response Oncogenic Cooperation: A New Mechanism of Cancer Cell Survival

The main tumor suppressor function of p53 as a "guardian of the genome" is to respond to cellular stress by transcriptional activation of apoptosis, growth arrest, or senescence in damaged cells. Not surprisingly, mutations in the p53 gene are the most frequent genetic alteration in human cancers. Importantly, mutant p53 (mutp53) proteins not only lose their wild-type tumor suppressor activity but also can actively promote tumor development. Two main mechanisms accounting for mutp53 proto-oncogenic activity are inhibition of the wild-type p53 in a dominant-negative fashion and gain of additional oncogenic activities known as gain-of-function (GOF). Here, we discuss a novel mechanism of mutp53 GOF, which relies on its oncogenic cooperation with the heat shock machinery. This coordinated adaptive mechanism renders cancer cells more resistant to proteotoxic stress and provides both, a strong survival advantage to cancer cells and a promising means for therapeutic intervention.