c-Myc In Cancer Cells Research Articles

The effect of Wnt/β-catenin signaling on PD-1/PDL-1 axis in HPV-related cervical cancer.

Infection with high-risk human papillomavirus (HPV), including HPV-16 and HPV-18, is the main cause of malignancies, such as cervical cancer. Viral oncoproteins encoded by HPV are expressed in HPV-positive cancers and associated with the early cancer stages and the transformation of normal cells. The signaling pathways involved in the transformation of normal cells to cancerous form and the subsequently expressed programmed cell death-ligand 1 (PD-L1) on the surface of the transformed cells lead to a disruption in recognition of tumor cells by the immune cell system, including T lymphocytes and dendritic cells which lead to the development of cervical cancer malignancy. These cells also produce modest levels of cytokines during exhaustion, tumor-infiltrating T CD4+ cells with high levels of PD-1 and CD39 release considerable quantities of cytokines. The Wnt/β-catenin signaling pathway, which controls the expression of genes involved in the tumor cells' markers, is demonstrated to be one of the most potent cancer stimulants. It leads to the evasion of the tumor cells from immune cell detection and ultimately avoids being recognized by dendritic cells or T-cells. PD-L1, as an inhibitory immune checkpoint, is essential for controlling immune system activity by inhibiting T-cells' inflammatory function. In the present review, we looked into how Wnt/β-catenin affects the expression of PD-L1 and related genes like c-MYC in cancer cells and its role in the development of HPV-induced malignancy. We hypothesized that blocking these pathways could be a potential immunotherapy and cancer prevention method.

MicroRNA-1254 Suppresses Epithelial-Mesenchymal Transition by Upregulating c-Cellular Myelocytomatosis Oncogene (c-Myc) and Alleviates Drug Resistance in Lung Cancer

Drug resistance is a huge challenge during the management of diseases. MicroRNA (miRNA) dys-regulation is known to contribute to tumor progression. Herein we aimed to explore miR-1254’s role in drug resistance in lung cancer. In the present study, we used Pabolizumab to treat drug-resistant and non-drug resistant lung cancer cells followed by analysis of miR-1254 expression by RT-qPCR, epithelial-mesenchymal transition (EMT) related protein and c-Myc expression by western blot, E-cadherin and N-cadherin level by immunofluorescence. Additionally, mouse model of lung cancer was treated with miR-1254 mimic and/or Pabolizumab to assess miR-1254’s role in lung cancerin vivo. Drug-resistant lung cancer cells exhibited significantly increased viability upon treatment with Pabolizumab with decreased miR-1254 expression. Besides, Pabolizumab upregulated E-caderin and downregulated N-cadherin. Importantly, miR-1254 bound to c-Myc in cancer cells. In the presence of miR-1254 mimic or siRNA (si)-c-Myc, the chemosensitivity of lung cancer cells was increased whereas miR-1254 inhibitor augmented cell resistance to Pabolizumab. Furthermore, the chemosensitivity induced by c-Myc could be depleted by miR-1254 inhibitor. Combined treatment of miR-1254 mimic and Pabolizumab significantly decreased tumor weight and volume, and reduced c-Myc level. In conclusion, miR-1254 might suppress EMT by inhibiting c-Myc expression in lung cancer and decrease drug resistance.

C-MYC-mediated TRIB3/P62+ aggresomes accumulation triggers paraptosis upon the combination of everolimus and ginsenoside Rh2

The mammalian target of rapamycin (mTOR) pathway is abnormally activated in lung cancer. However, the anti-lung cancer effect of mTOR inhibitors as monotherapy is modest. Here, we identified that ginsenoside Rh2, an active component of Panax ginseng C. A. Mey., enhanced the anti-cancer effect of the mTOR inhibitor everolimus both in vitro and in vivo. Moreover, ginsenoside Rh2 alleviated the hepatic fat accumulation caused by everolimus in xenograft nude mice models. The combination of everolimus and ginsenoside Rh2 (labeled Eve-Rh2) induced caspase-independent cell death and cytoplasmic vacuolation in lung cancer cells, indicating that Eve-Rh2 prevented tumor progression by triggering paraptosis. Eve-Rh2 up-regulated the expression of c-MYC in cancer cells as well as tumor tissues. The increased c-MYC mediated the accumulation of tribbles homolog 3 (TRIB3)/P62+ aggresomes and consequently triggered paraptosis, bypassing the classical c-MYC/MAX pathway. Our study offers a potential effective and safe strategy for the treatment of lung cancer. Moreover, we have identified a new mechanism of TRIB3/P62+ aggresomes-triggered paraptosis and revealed a unique function of c-MYC.

High-Throughput Screening and Triage Assays Identify Small Molecules Targeting c-MYC in Cancer Cells.

While c-MYC is well established as a proto-oncogene, its structure and function as a transcription factor have made c-MYC a difficult therapeutic target. To identify small-molecule inhibitors targeting c-MYC for anticancer therapy, we designed a high-throughput screening (HTS) strategy utilizing cellular assays. The novel approach for the HTS was based on the detection of cellular c-MYC protein, with active molecules defined as those that specifically decreased c-MYC protein levels in cancer cells. The assay was based on a dual antibody detection system using Förster/fluorescence resonance energy transfer (FRET) and was utilized to detect endogenous c-MYC protein in the MYC amplified cancer cell lines DMS273 and Colo320 HSR. The assays were miniaturized to 1536-well plate format and utilized to screen the GlaxoSmithKline small-molecule collection of approximately 2 million compounds. In addition to the HTS assay, follow-up assays were developed and used to triage and qualify compounds. Two cellular assays used to eliminate false-positive compounds from the initially selected HTS hits were (1) a cellular toxicity assay and (2) an unstable protein reporter assay. Three positive selection assays were subsequently used to qualify compounds: (1) 384-well cell cycle flow cytometry, (2) 384-well cell growth, and (3) c-MYC gene signature reverse transcription quantitative PCR (RT-qPCR). The HTS and follow-up assays successfully identified three compounds that specifically decreased c-MYC protein levels in cancer cells and phenocopied c-MYC siRNA in terms of cell growth inhibition and gene signatures. The HTS, triage, and three compounds identified are described.

Peroxynitrite promotes serine-62 phosphorylation-dependent stabilization of the oncoprotein c-Myc

Stabilization of c-Myc oncoprotein is dependent on post-translational modifications, especially its phosphorylation at serine-62 (S62), which enhances its tumorigenic potential. Herein we report that increase in intracellular superoxide induces phospho-stabilization and activation of c-Myc in cancer cells. Importantly, sustained phospho-S62 c-Myc was necessary for promoting superoxide dependent chemoresistance as non-phosphorylatable S62A c-Myc was insensitive to the redox impact when subjected to chemotherapeutic insults. This redox-dependent sustained S62 phosphorylation occurs through nitrative inhibition of phosphatase, PP2A, brought about by peroxynitrite, a reaction product of superoxide and nitric oxide. We identified a conserved tyrosine residue (Y238) in the c-Myc targeting subunit B56α of PP2A, which is selectively amenable to nitrative inhibition, further preventing holoenzyme assembly. In summary, we have established a novel mechanism wherein the pro-oxidant microenvironment stimulates a pro-survival milieu and reinforces tumor maintenance as a functional consequence of c-Myc activation through its sustained S62 phosphorylation via inhibition of phosphatase PP2A. Significance statementIncreased peroxynitrite signaling in tumors causes sustained S62 c-Myc phosphorylation by PP2A inhibition. This is critical to promoting c-Myc stabilization and activation which promotes chemoresistance and provides significant proliferative and growth advantages to osteosarcomas.

Flavonoids Luteolin and Quercetin Inhibit RPS19 and contributes to metastasis of cancer cells through c-Myc reduction

Flavonoids luteolin and quercetin can inhibit growth and metastasis of cancer cells. In our previous report, luteolin and quercetin was shown to block Akt/mTOR/c-Myc signaling. Here, we found luteolin and quercetin reduced protein level and transactivation activity of RPS19 in A431-III cells, which is isolated from parental A431 (A431-P) cell line. Further investigation the inhibitory mechanism of luteolin and quercetin on RPS19, we found c-Myc binding sites on RPS19 promoter. The Akt inhibitor LY294002, mTOR inhibitor rapamycin and c-Myc inhibitor 10058-F4 significantly suppressed RPS19 expression and transactivation activities. Overexpression and knockdown of c-Myc in cancer cells show RPS19 expression was regulated by c-Myc. Furthermore, Knockdown and overexpression of RPS19 was used to analyze of the function of RPS19 in cancer cells. The epithelial-mesenchymal transition (EMT) markers and metastasis abilities of cancer cells were also regulated by RPS19. These data suggest that luteolin and quercetin might inhibit metastasis of cancer cells by blocking Akt/mTOR/c-Myc signaling pathway to suppress RPS19-activated EMT signaling.

Inhibition of CIP2A attenuates tumor progression by inducing cell cycle arrest and promoting cellular senescence in hepatocellular carcinoma

CIP2A is a recent identified oncogene that inhibits protein phosphatase 2A (PP2A) and stabilizes c-Myc in cancer cells. To investigate the potential oncogenic role and prognostic value of CIP2A, we comprehensively analyzed the CIP2A expression levels in pan-cancer and observed high expression level of CIP2A in majority cancer types, including hepatocellular carcinoma (HCC). Based on a validation cohort including 60 HCC and 20 non-tumorous tissue samples, we further confirmed the high mRNA and protein expression levels of CIP2A in HCC, and found high CIP2A mRNA expression level was associated with unfavorable overall and recurrence-free survival in patients with HCC. Mechanistic investigations revealed that inhibition of CIP2A significantly attenuated cellular proliferation in vitro and tumourigenicity in vivo. Bioinformatic analysis suggested that CIP2A might be involved in regulating cell cycle. Our experimental data further confirmed CIP2A knockdown induced cell cycle arrest at G1 phase. We found accumulated cellular senescence in HCC cells with CIP2A knockdown, companying expression changes of senescence associated proteins (p21, CDK2, CDK4, cyclin D1, MCM7 and FoxM1). Mechanistically, CIP2A knockdown repressed FoxM1 expression and induced FoxM1 dephosphorylation. Moreover, inhibition of PP2A by phosphatase inhibitor rescued the repression of FoxM1. Taken together, our results showed that CIP2A was highly expressed in HCC. Inhibition of CIP2A induced cell cycle arrest and promoted cellular senescence via repressing FoxM1 transcriptional activity, suggesting a potential anti-cancer target for patients with HCC.

Silencing IGF-II impairs C-myc and N-ras expressions of SMMC-7721 cells via suppressing FAK/PI3K/Akt signaling pathway

Emerging evidence confirms that insulin-like growth factor -II (IGF-II), oncogenes C-myc and N-ras are an essential regulator for development and growth in hepatocellular carcinoma (HCC). Although our previous study also indicated that IGF-II might upregulate levels of oncogenes C-myc and N-ras in hepatoma carcinoma cells, the molecular mechanism had not been fully elucidated. Herein, we successfully silenced IGF-II expression in SMCC-7721 cells by small RNA interference. Functional analysis showed that knockdown of IGF-II significantly suppressed growth and proliferation of SMMC-7721 cells and decreased C-myc and N-ras mRNA and protein levels. And this function was mediated by the FAK/PI3K/Akt signaling pathway. Taken together, IGF-II siRNA inactivates the FAK/PI3K/Akt signaling pathway, and further reduces cell proliferation, N-ras and C-myc levels in SMMC-7721 cells. Especially, understanding the relationship between IGF-II and oncogenes N-ras and C-myc in cancer cells will provide novel clues for clinic HCC treatment in the future.

Targeting soluble CD146 with a neutralizing antibody inhibits vascularization, growth and survival of CD146-positive tumors.

CD146 (MUC-18, MCAM) expression on cancer cells correlates with cancer progression and a bad prognosis in several tumors, including melanoma and pancreatic tumors. Deciphering the mechanism mediating the CD146 role in cancer is essential for generating new therapeutic strategies. We found that CD146 expression in cancer cells is associated with a secretion of soluble CD146 (sCD146) that constitutes an active player in tumor development. Indeed, sCD146 induces the overexpression of its binding protein, angiomotin, on both endothelial and cancer cells and promotes both paracrine effects on angiogenesis and autocrine effects on cancer cells proliferation and survival. These last effects are mediated in part through the induction and phosphorylation of c-myc in cancer cells. In mice models xenografted with human CD146-positive melanoma or pancreatic cancer cells, administration of a novel monoclonal antibody specifically targeting sCD146, but not its membrane form, successfully suppresses tumor vascularization and growth. Our findings demonstrate that sCD146 secreted by CD146-positive tumors mediates important pro-angiogenic and pro-tumoral effects. Targeting sCD146 with a novel neutralizing antibody could thus constitute an innovative therapeutic strategy for the treatment of CD146-positive tumors.

UNBS1450 from Calotropis procera as a regulator of signaling pathways involved in proliferation and cell death

Despite significant progress in oncology therapeutics in the last decades, the urge to discover and to develop new, alternative or synergistic anti-cancer agents still remains. For centuries it has been known that the coarse shrub Calotropis procera is a very promising source of ascaricidal, schizonticidal, anti-bacterial, anthelmintic, insecticidal, anti-inflammatory, anti-diarrhoeal, larvicidal and cytotoxic chemicals. Different compounds like norditerpenic esters, organic carbonates, the cysteine protease procerain, alkaloids, flavonoids, sterols as well as numerous types of cardenolides have provided this plant for centuries with scientists’ interest. The chemical class of cardenolides and their related bioactivity evaluation and structure–activity relationship (SAR) studies pointed out their therapeutic utility and led to the discovery of promising drug candidates. Recently the cardiotonic steroid UNBS1450 01 (derived from 2-oxovoruscharin 02) from C. procera was shown to additionally exert an anti-cancer activity. UNBS1450 01 has been proven to be a potent sodium pump inhibitor, showing anti-proliferative and cell death-inducing activities. This anti-cancer potential of UNBS1450 01 is achieved by disorganization of the actin cytoskeleton after binding to the sodium pump at the cellular membrane, by inducing autophagy-related cell death, by repressing NF-κB activation as well as by down-regulating c-Myc in cancer cells. We aim to review pharmacologically important chemical extracts from C. procera and focus more specifically on the anti-cancer activities of UNBS1450 01.

Regulation of transferrin receptor 2 in human cancer cell lines

In a recent study we have explored TfR2 expression in a panel of cancer cell lines and we observed that about 40% of these cell lines clearly express TfR2. Taking advantage of this observation and considering the frequent overexpression of c-Myc in cancer cells we have explored the existence of a possible relationship between c-Myc and TfR2 in these cell lines. Our results provided evidence that TfR2 + cell lines express low c-Myc levels and low TfR1 levels, while TfR2 − cell lines express high c-Myc and TfR1 levels. Using the erythroleukemic K562 TfR2 + cells as a model, we observed that agents that enhance c-Myc expression, such as iron, determine a decrease of TfR2 expression, while molecules that induce a decreased c-Myc expression, such as the iron chelator desferoxamine or the kinase inhibitor ST 1571, induce an enhanced TfR2 expression. On the other hand, we have evaluated a possible effect of hypoxia and nitric oxide on TfR2 expression in erythroleukemia K526 and hepatoma HepG2 cells, providing evidence that: (i) agents inducing cellular hypoxia, such as CoCl 2, elicited a marked upmodulation of TfR1, but a downmodulation of TfR2 expression; (ii) NO + donors, such as sodium nitroprusside (SNP), induced a moderate decrease of TfR1, associated with a marked decline of TfR2 expression; (iii) NO donors, such as S-Nitroso-N-Acetylpenicillamine (SNAP), induced a clear increase of TfR1, associated with a moderate upmodulation of TfR2 expression. The ensemble of these observations suggests that in cancer cell lines TfR2 expression can be modulated through stimuli similar to those known to act on TfR1 and these findings may have important implications for our understanding of the role of TfR2 in the regulation of iron homeostasis.

BCL2 Is a Downstream Effector of MIZ-1 Essential for Blocking c-MYC-induced Apoptosis

The c-MYC oncoprotein is among the most potent transforming agents in human cells. Ironically, c-MYC is also capable of inducing massive apoptosis under certain conditions. A clear understanding of the distinct pathways activated by c-MYC during apoptosis induction and transformation is crucial to the design of therapeutic strategies aimed at selectively reactivating the apoptotic potential of c-MYC in cancer cells. We recently demonstrated that apoptosis induction in primary human cells strictly requires that c-MYC bind and inactivate the transcription factor MIZ-1. This presumably blocked the ability of MIZ-1 to activate the transcription of an unidentified pro-survival gene. Here we report that MIZ-1 activates the transcription of BCL2. More importantly, inhibition of the MIZ-1/BCL2 signal is an essential event during the apoptotic response. Furthermore, targeting BCL2 with short hairpin RNA or small molecule inhibitors restores the apoptotic potential of a c-MYC mutant that is defective for MIZ-1 inhibition. These observations suggest that repression of BCL2 transcription is the single essential consequence of targeting the MIZ-1 pathway during apoptosis induction. These data define a genetic pathway that helps to explain historical observations documenting cooperation between c-MYC and BCL2 overexpression in human cancer.

Dodging Death, Creating Cancer with Wnt

Teasing apart the actions of oncogenes, which often stimulate apoptotic signaling along with growth-promoting signals, has proven a challenging puzzle, particularly when interactions with other signaling pathways are also integrated into the biological response. You et al. describe experiments that help clarify the interaction of the c-Myc oncogene product with the Wnt--β-catenin signaling. Because Wnt signaling is enhanced in various human cancers and often correlates with increased expression of c-Myc, it might seem that Myc provides a growth-stimulatory effect to cooperate with Wnt signals. However, the data by You et al. suggest that a critical aspect of the interaction is actually for Wnt signals to inhibit Myc's effects that induce apoptosis. Furthermore, Wnt-1 and cMyc cooperated to promote tumor formation when cells expressing both proteins were injected in nude mice. Cyclooxygenase 2 and WISP-1 [Wnt-1 induced secreted protein 1, a member of the CCN (connective tissue growth factor-Cyr61-NOV) family of growth factors] were identified as potential mediators of the effect of Wnt to blunt apoptotic signals. The authors suggest that increased expression of Wnt and c-Myc in cancer cells may allow the cells to tolerate the apoptotic effects of Myc, thus favoring oncogenic transformation. Z. You, D. Saims, S. Chen, Z. Zhang, D. C. Guttridge, K. Guan, O. A. MacDougald, A. M.C. Brown, G. Evan, J. Kitajewski, C. -Y. Wang, Wnt signaling promotes oncogenic transformation by inhibiting c-Myc-induced apoptosis. J. Cell Biol. 157 , 429-440 (2002) [Abstract] [Full Text]