Ionizing radiation normalizes the features of active breast cancer stromal fibroblasts and suppresses their paracrine pro-carcinogenic effects.

Background: Radiotherapy is an important therapeutic strategy for breast cancer patients through reducing the chances of recurrence and metastasis, which are fueled by cancer-associated fibroblasts (CAFs). Thereby, we addressed here the effect of various doses of X-rays on breast CAFs and their adjacent counterparts.

Methods: We have used WST1 and annexin V-associated with flow cytometry to test the cytotoxic effects of X-rays.

AUF1 promotes stemness in human mammary epithelial cells through stabilization of the EMT transcription factors TWIST1 and SNAIL1.

The AU-rich element RNA-binding protein 1 (AUF1) is an RNA-binding protein, which can both stabilize and destabilize the transcripts of several cancer-related genes. Since epithelial-to-mesenchymal transition (EMT) and the acquisition of cancer stem cell traits are important for cancer onset and progression, we sought to determine the role of AUF1 in these two important processes. We have shown that AUF1 induces EMT and stemness in breast epithelial cells via stabilization of the SNAIL1 and TWIST1 mRNAs, and their consequent upregulation.

Interleukin-8 Dedifferentiates Primary Human Luminal Cells to Multipotent Stem Cells.

During aging, cellular plasticity and senescence play important roles in tissue regeneration and the pathogenesis of different diseases, including cancer. We have recently shown that senescent breast luminal cells can activate their adjacent stromal fibroblasts. In the present report, we present clear evidence that these senescence-related active fibroblasts can dedifferentiate proliferating primary human luminal cells to multipotent stem cells in an interleukin-8 (IL-8)-dependent manner.

AUF1 positively controls angiogenesis through mRNA stabilization-dependent up-regulation of HIF-1α and VEGF-A in human osteosarcoma.

Osteosarcoma is the most common malignant bone tumor in children, adolescents, and young adults. This pleiomorphic tumor depends on new blood vessel development, also known as angiogenesis, for tumor growth and metastasis. Therefore, it's of utmost importance to identify the key genes and pathways that regulate this pro-metastatic process in order to develop more efficient therapies.

Senescent Breast Luminal Cells Promote Carcinogenesis through Interleukin-8-Dependent Activation of Stromal Fibroblasts.

Aging and stress promote senescence, which has intrinsic tumor suppressor functions and extrinsic tumor promoting properties. Therefore, it is of utmost importance to delineate the effects of senescence inducers on the various types of cells that compose the different organs. We show here that primary normal breast luminal (NBL) cells are more sensitive than their corresponding stromal fibroblasts to proliferative as well as oxidative damage-induced senescence.

Interleukin-8 Activates Breast Cancer-Associated Adipocytes and Promotes Their Angiogenesis- and Tumorigenesis-Promoting Effects.

Increasing evidence supports the critical role of active stromal adipocytes in breast cancer development and spread. However, the mediators and the mechanisms of action are still elusive. We show here that cancer-associated adipocytes (CAAs) isolated from 10 invasive breast carcinomas are proinflammatory and exhibit active phenotypes, including higher proliferative, invasive, and migratory capacities compared to their adjacent tumor-counterpart adipocytes (TCAs).

p16 Controls p53 Protein Expression Through miR-dependent Destabilization of MDM2.

p16 and p53 are two major tumor suppressor proteins that are both upregulated in response to various cellular stresses and during senescence and aging. p53 is a well-characterized transcription factor, while p16 a cyclin-dependent kinase inhibitor encoded by the gene, and controls the expression of several genes through protein-protein interactions and also via miRNAs. This report demonstrates a p16-dependent positive regulation of p53 expression, at the protein level, in various human cells as well as in mouse embryonic fibroblasts.

Obesity and p16 Downregulation Activate Breast Adipocytes and Promote Their Protumorigenicity.

Obesity is increasingly recognized as a risk factor for breast cancer development. However, the molecular basis of obesity-related breast carcinogenesis remains elusive. In this study, we have shown that obesity reduces the level of the tumor suppressor p16 protein in breast adipocytes, which showed active features and strong procarcinogenic potential both and in orthotopic tumor xenografts compared to mature adipocytes from lean women.

p16 enhances the transcriptional and the apoptotic functions of p53 through DNA-dependent interaction.

p16 and p53 are two important tumor suppressor proteins that play essential roles during cell proliferation and aging through regulating the expression of several genes. Here, we report that p16 and p53 co-regulate a plethora of transcripts. Furthermore, both proteins colocalize in the nucleus of human primary skin fibroblasts and breast luminal cells, and form a heteromer whose level increases in response to genotoxic stress as well as aging of human fibroblasts and various mouse organs.

p16 induces senescence and inhibits EMT through microRNA-141/microRNA-146b-5p-dependent repression of AUF1.

Senescence and epithelial-to-mesenchymal transition (EMT) processes are under the control of common tumor suppressor proteins, EMT transcription factors, and microRNAs. However, the molecular mechanisms that coordinate the functional link between senescence and EMT are still elusive. We have shown here that p16 -related induction of senescence is mediated through miR-141 and miR-146b-5p.

PAC down-regulates estrogen receptor alpha and suppresses epithelial-to-mesenchymal transition in breast cancer cells.

Background: Triple-negative breast cancer (TNBC) is an aggressive histological subtype with limited treatment options and very poor prognosis following progression after standard chemotherapeutic regimens. Therefore, novel molecules and therapeutic options are urgently needed for this category of patients. Recently, we have identified PAC as a curcumin analogue with potent anti-cancer features.

PAC exhibits potent anti-colon cancer properties through targeting cyclin D1 and suppressing epithelial-to-mesenchymal transition.

Colorectal cancer (CRC) is a major cause of cancer morbidity and mortality worldwide. Although response rates and overall survival have been improved in recent years, resistance to multiple drug combinations is inevitable. Therefore, the development of more efficient drugs, with fewer side effects is urgently needed.

MicroRNA-141 and microRNA-146b-5p inhibit the prometastatic mesenchymal characteristics through the RNA-binding protein AUF1 targeting the transcription factor ZEB1 and the protein kinase AKT.

miR-141 and miR-146b-5p are two important tumor suppressor microRNAs, which control several cancer-related genes and processes. In the present report, we have shown that these microRNAs bind specific sites at the 3'-untranslated region (UTR) of the mRNA-binding protein AUF1, leading to its down-regulation. This inverse correlation between the levels of these microRNAs and AUF1 has been identified in various osteosarcoma cell lines.

The cytokine IL-6 reactivates breast stromal fibroblasts through transcription factor STAT3-dependent up-regulation of the RNA-binding protein AUF1.

The development and spread of mammary carcinomas require synergetic interplay between tumor cells and their microenvironment through paracrine secretions, which are still not well defined. We have shown here that interleukin-6 (IL-6), either recombinant or secreted from highly invasive breast cancer cells, down-regulates the tumor suppressor proteins p16(INK4A), p21(WAF1), and p53 and activates breast stromal fibroblasts in a paracrine manner. The formation of myofibroblasts requires p16(INK4A) down-regulation and the activation of the JAK2/STAT3 pathway.

The cyclin-dependent kinase inhibitor p16INK4a physically interacts with transcription factor Sp1 and cyclin-dependent kinase 4 to transactivate microRNA-141 and microRNA-146b-5p spontaneously and in response to ultraviolet light-induced DNA damage.

p16(INK4a) is a tumor suppressor protein involved in several stress-related cellular responses, including apoptosis. Recent lines of evidence indicate that p16(INK4a) is also a modulator of gene expression. However, the molecular mechanisms underlying this novel function are still obscure.

p16(INK4A) positively regulates p21(WAF1) expression by suppressing AUF1-dependent mRNA decay.

Background: p16(INK4a) and p21(WAF1) are two independent cyclin-dependent kinase inhibitors encoded by the CDKN2A and CDKN1A genes, respectively. p16(INK4a) and p21(WAF1) are similarly involved in various anti-cancer processes, including the regulation of the critical G1 to S phase transition of the cell cycle, senescence and apoptosis. Therefore, we sought to elucidate the molecular mechanisms underlying the link between these two important tumor suppressor proteins.

ATR controls the UV-related upregulation of the CDKN1A mRNA in a Cdk1/HuR-dependent manner.

Ultraviolet (UV) light is a carcinogenic agent that upregulates the expression of several genes involved in various cellular processes, including cell cycle checkpoints and apoptosis. The universal cyclin-dependent kinase inhibitor p21(WAF1/Cip1) plays major roles in these processes, and the level of its corresponding message increases several times in response to UV-induced DNA damage. This upregulation is mainly posttranscriptional owing to HuR-dependent mRNA stabilization.

Curcumin triggers p16-dependent senescence in active breast cancer-associated fibroblasts and suppresses their paracrine procarcinogenic effects.

Activated cancer-associated fibroblasts (CAFs) or myofibroblasts not only facilitate tumor growth and spread but also affect tumor response to therapeutic agents. Therefore, it became clear that efficient therapeutic regimens should also take into account the presence of these supportive cells and inhibit their paracrine effects. To this end, we tested the effect of low concentrations of curcumin, a pharmacologically safe natural product, on patient-derived primary breast CAF cells.

Survivin expression increases during aging and enhances the resistance of aged human fibroblasts to genotoxic stress.

Survivin, an important anti-apoptotic protein, is highly expressed in most cancers, which generally arise in cells of older individuals. We have shown here accumulation of survivin and phospho-survivin in aged normal human skin fibroblasts and mice organs. This age-related accumulation of survivin was due to protein stabilization through association with the molecular chaperone Hsp90 protein, which was also up-regulated during aging.

ATR controls the p21(WAF1/Cip1) protein up-regulation and apoptosis in response to low UV fluences.

The universal cyclin-dependent kinase inhibitor p21(WAF1/Cip1) promotes cell cycle arrest and inhibits apoptosis in response to UV-induced DNA damage. Since the protein kinase ATR plays a major role in the cellular response to these carcinogenic lesions, we investigated the possible role of ATR in the modulation of p21(WAF1/Cip1) expression in response to UVC radiation. We have shown that p21(WAF1/Cip1) is up-regulated in human fibroblast and epithelial cells, but only in response to low UV fluences and low passage cells.

p16( INK4a) positively regulates cyclin D1 and E2F1 through negative control of AUF1.

Background: The cyclin-D/CDK4,6/p16(INK4a)/pRB/E2F pathway, a key regulator of the critical G1 to S phase transition of the cell cycle, is universally disrupted in human cancer. However, the precise function of the different members of this pathway and their functional interplay are still not well defined.

Methodology/principal Findings: We have shown here that the tumor suppressor p16(INK4a) protein positively controls the expression of cyclin D1 and E2F1 in both human and mouse cells.

The atr protein kinase controls UV-dependent upregulation of p16INK4A through inhibition of Skp2-related polyubiquitination/degradation.

The tumor suppressor p16(INK4A), a phosphoprotein that exists in human cells under both phosphorylated and nonphosphorylated forms, plays crucial roles during the cellular response to UV light. However, it is still unclear how this protein is activated in response to this carcinogenic agent. We have shown here that UVC upregulates p16(INK4A) and the phosphorylated form of the protein at the 4 serine sites; Ser-7, Ser-8, Ser-140, and Ser-152.

Expression of survivin and p16(INK4a)/Cdk6/pRB proteins and induction of apoptosis in response to radiation and cisplatin in meningioma cells.

Although meningiomas represent the most common class of tumors of the central nervous system, the molecular events underlying their genesis and development are still not well defined, and therapeutic approaches based on the genetics of these tumors are currently lacking. In the present study we have used the immunoblotting technique to show that the p16(INK4A), Cdk6 and pRB proteins are differentially expressed in primary meningioma cells with 20-, 30- and 36-fold difference between the lowest and the highest levels of each protein, respectively. In addition, we present evidence that the level of the anti-apoptosis survivin protein is high in these benign tumors.

The p53/p21 DNA damage-signaling pathway is defective in most meningioma cells.

Although meningiomas represent the most common class of tumors of the central nervous system, the molecular events underlying their genesis and development are still not well defined. In the present study we have used the immuno-blotting technique to study the expression level of the tumor suppressor proteins p53, p21 and PTEN in primary meningioma cells. We have also studied the induction of p21 and p53 in response to both UV light and gamma-rays.

The p16INK4a tumor suppressor controls p21WAF1 induction in response to ultraviolet light.

p16INK4a and p21WAF1, two major cyclin-dependent kinase inhibitors, are the products of two tumor suppressor genes that play important roles in various cellular metabolic pathways. p21WAF1 is up-regulated in response to different DNA damaging agents. While the activation of p21WAF1 is p53-dependent following -rays, the effect of ultraviolet (UV) light on p21WAF1 protein level is still unclear.