AKT is indispensable for coordinating Par-4/JNK cross talk in p21 downmodulation during ER stress

p21Waf1/Cip1 Is a Novel Downstream Target of 40S Ribosomal S6 Kinase 2

Background/Objectives: The ribosomal S6 kinase 2 (S6K2) acts downstream of the mechanistic target of rapamycin complex 1 and is a homolog of S6K1 but little is known about its downstream effectors. The objective of this study was to use an unbiased transcriptome profiling to uncover how S6K2 promotes breast cancer cell survival. Methods: RNA-Seq analysis was performed to identify novel S6K2 targets. Cells were transfected with siRNAs or plasmids containing genes of interest. Western blot analyses were performed to quantify total and phosphorylated proteins. Apoptosis was monitored by treating cells with different concentrations of doxorubicin. Results: Silencing of S6K2, but not S6K1, decreased p21 in MCF-7 and T47D breast cancer cells. Knockdown of Akt1 but not Akt2 decreased p21 in MCF-7 cells whereas both Akt1 and Akt2 knockdown attenuated p21 in T47D cells. While Akt1 overexpression enhanced p21 and partially reversed the effect of S6K2 deficiency on p21 downregulation in MCF-7 cells, it had little effect in T47D cells. S6K2 knockdown increased JUN mRNA and knockdown of cJun enhanced p21. Low concentrations of doxorubicin increased, and high concentrations decreased p21 levels in T47D cells. Silencing of S6K2 or p21 sensitized T47D cells to doxorubicin via c-Jun N-terminal kinase (JNK)-mediated downregulation of Mcl-1. Conclusions: S6K2 knockdown enhanced doxorubicin-induced apoptosis by downregulating the cell cycle inhibitor p21 and the anti-apoptotic protein Mcl-1 via Akt and/or JNK.

EGCG inhibits the inflammation and senescence inducing properties of MDA-MB-231 triple-negative breast cancer (TNBC) cells-derived extracellular vesicles in human adipose-derived mesenchymal stem cells

BACKGROUND

Triple-negative breast cancer (TNBC) cells' secretome can induce a pro-inflammatory phenotype in human adipose-derived mesenchymal stem cells (hADMSC). This can be prevented by the green tea polyphenol epigallocatechin-3-gallate (EGCG). The impact of EGCG on the paracrine regulation that the extracellular vesicles (EVs) specifically exert within the TNBC secretome remains unknown.

METHODS

EVs were obtained from a TNBC-derived serum-starved MDA-MB-231 cell model treated or not with EGCG under normoxic or hypoxic (< 1% O2) culture conditions. RNA-Seq analysis was used to assess the EVs' genetic content. The modulation of inflammatory and senescence markers in hADMSC was evaluated by RT-qPCR using cDNA arrays and validated by immunoblotting. A protein profiler phospho-kinase array was used to explore signaling pathways.

RESULTS

While hypoxic culture conditions did not significantly alter the genetic content of MDA-MB-231-secreted EVs, the addition of EGCG significantly modified EVs genetic material at low oxygen tension. Gene expression of cancer-associated adipocyte pro-inflammatory markers CXCL8, CCL2 and IL-1β was increased in hADMSC treated with EVs. Concomitantly, EVs isolated from MDA-MB-231 treated with EGCG (EGCG-EVs) downregulated CCL2 and IL-1β, while inducing higher expression of CXCL8 and IL-6 levels. EVs activated CHK-2, c-Jun, AKT and GSK-3β signaling pathways in hADMSC, whereas EGCG-EVs specifically reduced the latter two as well as the serum starvation-induced senescence markers p21 and β-galactosidase. Finally, the mitochondrial content within the TNBC cells-derived EVs was found reduced upon EGCG treatment.

CONCLUSION

This proof of concept study demonstrates that the chemopreventive properties of diet-derived polyphenols may efficiently target the paracrine regulation that TNBC cells could exert upon their surrounding adipose tissue microenvironment.

Repurposing gestrinone for tumor suppressor through P21 reduction regulated by JNK in gynecological cancer

Endometriosis has been shown to increase the risk of gynecological cancers. However, the effect of gestrinone, a clinical endometriosis drug, on gynecological cancers remains unclear. This study aimed to understand the effect of gestrinone on gynecological cancers. A retrospective study was conducted using the Longitudinal Health Insurance Database 2000 of the Taiwan National Health Insurance Research Database (NHIRD) to observe the risk of gynecological cancers. Medication records from the Department of Obstetrics and Gynecology, Chung Shan Medical University Hospital CSMUH and cancer records from the Taiwan Cancer Registry were collected to analyze the correlation between gestrinone use and gynecological cancers. Subsequently, human cell lines were used to investigate the effect of gestrinone on gynecological cancers. A total of 8330 endometriosis patients were enrolled, and analyses revealed that endometriosis patients had a higher risk of developing ovarian and endometrial cancer. However, the rate of cervical cancer was not statistically different (P = 0.249). Analyses of both the NHIRD and CSMUH databases revealed that gestrinone may reduce the risk of gynecological cancer. Cellular experiments verified the anticancer effects of gestrinone, which effectively and specifically inhibited the growth of HeLa cervical cancer cells, decreased P21 expression via JNK phosphorylation, and induced apoptosis. Combining the results of clinical database analysis and cell experiments, our findings prove that gestrinone has the potential to protect against cancer through regulation of the JNK-P21 axis. Repurposing the anticancer efficacy of gestrinone may be a strategy for targeted therapy in the future.

Transforming Growth Factor-Beta (TGF-β) Signaling in Cancer-A Betrayal Within

A ubiquitously expressed cytokine, transforming growth factor-beta (TGF-β) plays a significant role in various ongoing cellular mechanisms. The gain or loss-of-function of TGF-β and its downstream mediators could lead to a plethora of diseases includes tumorigenesis. Specifically, at the early onset of malignancy TGF-β act as tumour suppressor and plays a key role in clearing malignant cells by reducing the cellular proliferation and differentiation thus triggers the process of apoptosis. Subsequently, TGF-β at an advanced stage of malignancy promotes tumorigenesis by augmenting cellular transformation, epithelial-mesenchymal-transition invasion, and metastasis. Besides playing the dual roles, depending upon the stage of malignancy, TGF-β also regulates cell fate through immune and stroma components. This oscillatory role of TGF-β to fight against cancer or act as a traitor to collaborate and crosstalk with other tumorigenic signaling pathways and its betrayal within the cell depends upon the cellular context. Therefore, the current review highlights and understands the dual role of TGF-β under different cellular conditions and its crosstalk with other signaling pathways in modulating cell fate.

Tamarix articulata Inhibits Cell Proliferation, Promotes Cell Death Mechanisms and Triggers G0/G1 Cell Cycle Arrest in Hepatocellular Carcinoma Cells

RESEARCH BACKGROUND

From ancient times plants have been used for medicinal purposes against various ailments. In the modern era, plants are a major source of drugs and are an appealing drug candidate for the anticancer therapeutics against various molecular targets. Here we tested methanolic extract of dry leaves of Tamarix articulata for anticancer activity against a panel of hepatocellular carcinoma cells.

EXPERIMENTAL APPROACH

Cell viability of hepatocellular carcinoma cells was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay after a dose-dependent treatment with the extract of T. articulata. Phase-contrast microscopy and 4՛,6-diamidino-2-phenylindole (DAPI) staining served to analyse cellular and nuclear morphology. Immunoblotting was performed to determine the expression of proteins associated with autophagy, apoptosis and cell cycle. However, flow cytometry was used for the quantification of apoptotic cells and the analysis of cells in different phases of the cycle after the treatment with various doses of T. articulata. Additionally, acridine orange staining and 2՛,7՛-dichlorofluorescein diacetate (DCFH-DA) dye were used to analyse the quantification of autophagosomes and reactive oxygen species.

RESULTS AND CONCLUSION

Our results demonstrate that T. articulata methanolic extract exhibits promising antiproliferative activity with IC50 values (271.1±4.4), (298.3±7.1) and (336.7±6.1) µg/mL against hepatocellular carcinoma HepG2, Huh7D12 and Hep3B cell lines, respectively. Mechanistically, we found that T. articulata methanolic extract induces cell death by activating apoptosis and autophagy pathways. First, T. articulata methanolic extract promoted autophagy, which was confirmed by acridine orange staining. The immunoblotting analysis further confirmed that the extract at higher doses consistently induced the conversion of LC3I to LC3II form with a gradual decrease in the expression of autophagy substrate protein p62. Second, T. articulata methanolic extract promoted reactive oxygen species production in hepatocellular carcinoma cells and activated reactive oxygen species-mediated apoptosis. Flow cytometry and immunoblotting analysis showed that the plant methanolic extract induced dose-dependent apoptosis and activated proapoptotic proteins caspase-3 and PARP1. Additionally, the extract triggered the arrest of the G0/G1 phase of the cell cycle and upregulated the protein expression of p27/Kip and p21/Cip, with a decrease in cyclin D1 expression in hepatocellular carcinoma cells.

NOVELTY AND SCIENTIFIC CONTRIBUTION

The current study demonstrates that T. articulata methanolic extract exhibits promising anticancer potential to kill tumour cells by programmed cell death type I and II mechanisms and could be explored for potential drug candidate molecules to curtail cancer in the future.

Natural podophyllotoxin analog 4DPG attenuates EMT and colorectal cancer progression via activation of checkpoint kinase 2

Epithelial–mesenchymal transition (EMT) is critical for the metastatic dissemination of cancer cells and contributes to drug resistance. In this study, we observed that epithelial colorectal cancer (CRC) cells transiently exposed to 5-fluorouracil (5-FU) (a chemotherapeutic drug for CRC) as well as 5-FU-resistant cells (5-FU-R) develop EMT characters as evidenced by activation of Vimentin and augmented invasive properties. On the other hand, 4DPG (4′-demethyl-deoxypodophyllotoxin glucoside), a natural podophyllotoxin analog attenuates EMT and invadopodia formation abilities of HCT-116/5-FU-R and SW-620/5-FU-R cells. Treatment with 4DPG restrains Vimentin phosphorylation (Ser38) in 5-FU-R cells, along with downregulation of mesenchymal markers Twist1 and MMP-2 while augmenting the expression of epithelial markers E-cadherin and TIMP-1. Moreover, 4DPG boosts the tumor-suppressor protein, checkpoint kinase 2 (Chk2) via phosphorylation at Thr68 in a dose-dependent manner in 5-FU-R cells. Mechanistically, SiRNA-mediated silencing of Chk2, as well as treatment with Chk2-specific small-molecule inhibitor (PV1019), divulges that 4DPG represses Vimentin activation in a Chk2-dependent manner. Furthermore, immunoprecipitation analysis unveiled that 4DPG prevents complex formation between Vimentin and p53 resulting in the rescue of p53 and its nuclear localization in aggressive 5-FU-R cells. In addition, 4DPG confers suitable pharmacokinetic properties and strongly abrogates tumor growth, polyps formation, and lung metastasis in an orthotopic rat colorectal carcinoma model. In conclusion, our findings demonstrate 4DPG as a targeted antitumor/anti-metastatic pharmacological lead compound to circumvent EMT-associated drug resistance and suggest its clinical benefits for the treatment of aggressive cancers.

Lysine Deprivation Induces AKT-AADAT Signaling and Overcomes EGFR-TKIs Resistance in EGFR-Mutant Non-Small Cell Lung Cancer Cells

Simple Summary

In the Asian population, 50–60% of non-small cell lung cancer (NSCLC) patients carry the epidermal growth factor receptor (EGFR) mutation. Although treatment with EGFR-tyrosine kinase inhibitors (EGFR-TKIs) is effective, resistance inevitably occurs. Moreover, previous studies showed that cancers harboring a specific mutation are sensitive to deficiency related to a particular amino acid. The identity of this amino acid is, however, unclear in the case of EGFR-mutant NSCLC. Our studies aim to identify the critical amino acid affected in EGFR-mutant NSCLC and develop a strategy against EGFR-TKI resistance. We determined that lysine is essential for the survival of EGFR-mutant NSCLC and EGFR-TKI-resistant sublines. In addition, we found that the presence of lysine reduction can lower the dosage of EGFR-TKI required for treatment in the case of EGFR-mutant NSCLC. Lastly, our findings provide a guiding principle showing that amino acid stress can enhance not only the therapeutic potential but also the quality of life for EGFR-mutant NSCLC patients.

Abstract

Epidermal growth factor receptor (EGFR) mutations are the most common driver genes in non-small cell lung cancer (NSCLC), especially in the Asian population. Although EGFR-tyrosine kinase inhibitors (TKIs) are influential in the treatment of EGFR-mutant NSCLC patients, acquired resistance inevitably occurs. Therefore, there is an urgent need to develop strategies to overcome this resistance. In addition, cancer cells with particular mutations appear more vulnerable to deficiency related to the availability of specific amino acids. However, it is still unknown which amino acid is affected in the case of EGFR-mutant NSCLC. In the present study, we established a screening platform based on amino acid deprivation and found that EGFR-mutant NSCLC cells are sensitive to short-term lysine deprivation. Moreover, we found that expression of the gene for the lysine catabolism enzyme α-aminoadipate aminotransferase (AADAT) increased under lysine deprivation, revealing that AADAT can be regulated by EGFR–AKT signaling. Finally, we found that lysine reduction can not only enhance the cytostatic effect of single-agent osimertinib but also overcome the resistance of EGFR-TKIs in EGFR-mutant NSCLC cells. In summary, our findings suggest that the introduction of lysine stress might act as an advancement in EGFR-mutant NSCLC therapy and offer a strategy to overcome EGFR-TKI resistance.

125I seeds irradiation inhibits tumor growth and induces apoptosis by Ki-67, P21, survivin, livin and caspase-9 expression in lung carcinoma xenografts

BACKGROUND

Lung cancer is a fatal disease and a serious health problem worldwide. Patients are usually diagnosed at an advanced stage, and the effectiveness of chemotherapy for such patients is very limited. Iodine 125 seed (¹²⁵I) irradiation can be used as an important adjuvant treatment for lung carcinoma. The purpose of this study was to examine the role of irradiation by 125I seeds in human lung cancer xenograft model and to determine the underlying mechanisms involved, with a focus on apoptosis.

METHODS

40 mice with A549 lung adenocarcinoma xenografts were randomly divided into 4 groups: control group (n = 10), sham seed (0 mCi) implant group (n = 10), 125I seed (0.6 mCi) implant group (n = 10) and 125I seed (0.8 mCi) implant group (n = 10), respectively. The body weight and tumor volume, were recorded every 4 days until the end of the study. Apoptotic cells were checked by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay and activities of caspase-3 and caspase-8 enzyme were tested. Expression of P21, survivin, livin, caspase-9 and proliferating cell nuclear antigen (Ki-67) was detected with immunohistochemical staining.

RESULTS

The results of TUNEL staining assays showed that 125I seed irradiation suppresses the growth of lung cancer xenografts in nude mice and induced apoptosis. The activity of caspase-3 and caspase-8 was significantly higher. The expression levels Ki67, survivin and livin were substantially downregulated, while P21 and caspase-9 protein expression were significantly increased following 125I seed irradiation. This study revealed that 125I seed irradiation could significantly change apoptosis-related protein in human lung cancer xenografts.

CONCLUSIONS

Overall, our study demonstrates that radiation exposure by 125I seeds could be a new treatment option for lung cancer.

Par-4 mediated Smad4 induction in PDAC cells restores canonical TGF-β/ Smad4 axis driving the cells towards lethal EMT

Deregulation of TGF-β signaling is intricately engrossed in the pathophysiology of pancreatic adenocarcinomas (PDACs). The role of TGF-β all through pancreatic cancer initiation and progression is multifarious and somewhat paradoxical. TGF-β plays a tumor suppressive role in early-stage pancreatic cancer by promoting apoptosis and inhibiting epithelial cell cycle progression, but incites tumor promotion in late-stage by modulating genomic instability, neo-angiogenesis, immune evasion, cell motility, and metastasis. Here, we provide evidences that Par-4 acts as one of the vital mediators to regulate TGF-β/Smad4 pathway, wherein, Par-4 induction/over-expression induced EMT which was later culminated in to apoptosis in presence of TGF-β via positive regulation of Smad4. Intriguingly, Par-4^-/- cells were devoid of significant Smad4 induction compared to Par-4^+/+ cells in presence of TGF-β and ectopic Par-4 steadily augmented Smad4 expression by restoring TGF-β/Smad4 axis in Panc-1 cells. Further, our FACS and western blotting results unveiled that Par-4 dragged the PDAC cells to G₁ arrest in presence of TGF-β byelevating p21 and p27 levels while attenuating Cyclin E and A levels and augmenting caspase 3 cleavage triggering lethal EMT. Through restoration of Smad4, we further establish that in BxPC3 cell line (Smad4^-/-), Smad4 is essential for Par-4 to indulge TGF-β dependent lethal EMT program. The mechanistic relevance of Par-4 mediated Smad4 activation was additionally validated by co-immunoprecipitation wherein disruption of NM23H1-STRAP interaction by Par-4 rescues TGF-β/Smad4 pathway in PDAC and mediates the tumor suppressive role of TGF-β, therefore serving as a vital cog to restore the apoptotic functions of TGF-β pathway.

Annurca apple polyphenol extract selectively kills MDA-MB-231 cells through ROS generation, sustained JNK activation and cell growth and survival inhibition

Polyphenols represent the most studied class of nutraceuticals that can be therapeutics for a large spectrum of diseases, including cancer. In this study, we investigated for the first time the antitumor activities of polyphenol extract from Annurca apple (APE) in MDA-MB-231 triple negative breast cancer cells, and we explored the underlying mechanisms. APE selectively inhibited MDA-MB-231 cell viability and caused G2/M phase arrest associated with p27 and phospho-cdc25C upregulation and with p21 downregulation. APE promoted reactive oxygen species (ROS) generation in MDA-MB-231 cells while it acted as antioxidant in non-tumorigenic MCF10A cells. We demonstrated that ROS generation represented the primary step of APE antitumor activity as pretreatment with antioxidant N-acetylcysteine (NAC) prevented APE-induced G2/M phase arrest, apoptosis, and autophagy. APE downregulated Dusp-1 and induced a significant increase in JNK/c-Jun phosphorylation that were both prevented by NAC. Moreover, downregulation of JNK by its specific inhibitor SP600125 significantly diminished the anticancer activity of APE indicating that ROS generation and sustained JNK activation represented the main underlying mechanism of APE-induced cell death. APE also inhibited AKT activation and downregulated several oncoproteins, such as NF-kB, c-myc, and β-catenin. In light of these results, APE may be an attractive candidate for drug development against triple negative breast cancer.

Involvement of Akt in mitomycin C and its analog triggered cytotoxicity in MCF-7 and K562 cancer cells

Mitomycin C (MC) is a well-known DNA alkylating agent. MC analog, 10-decarbamoyl mitomycin C (DMC), unlike MC, has stronger effects on cancer with p53 mutation. We previously demonstrated that MC/DMC could activate p21WAF1/CIP1 in MCF-7 (p53-proficient) and K562 (p53-deficient) cells in a p53-independent mode. This study aimed to elucidate the upstream signaling pathway of p21WAF1/CIP1 activation triggered by MC/DMC. Besides p53, Akt plays an important role on deactivating p21WAF1/CIP1 . The results showed that MC/DMC inhibited Akt in MCF-7 cells, but not in K562 cells. By knocking down p53, the Akt inhibition in MCF-7 cells was alleviated. This implied that the deactivated Akt caused by MC/DMC was p53-dependent. With Akt activator (SC79), p21WAF1/CIP1 activation triggered by MC/DMC in MCF-7 cells was not reduced. This indicated that Akt inhibition triggered by MC/DMC was not associated with MC/DMC-induced p21WAF1/CIP1 activation. Label-free quantitative proteomic profiling analysis revealed that DMC has a stronger effect on down-regulating the PI3K/Akt signaling pathway in MCF-7 cells as compared to MC. No significant effect of MC/DMC on PI3K/Akt in K562 cells was observed. In summary, MC/DMC regulate Akt activation in a p53-dependent manner. This Akt deactivation is not associated with p21WAF1/CIP1 activation in response to MC/DMC.

Novel role of prostate apoptosis response-4 tumor suppressor in B-cell chronic lymphocytic leukemia

Prostate apoptosis response-4 (Par-4), a proapoptotic tumor suppressor protein, is downregulated in many cancers including renal cell carcinoma, glioblastoma, endometrial, and breast cancer. Par-4 induces apoptosis selectively in various types of cancer cells but not normal cells. We found that chronic lymphocytic leukemia (CLL) cells from human patients and from Eµ-Tcl1 mice constitutively express Par-4 in greater amounts than normal B-1 or B-2 cells. Interestingly, knockdown of Par-4 in human CLL-derived Mec-1 cells results in a robust increase in p21/WAF1 expression and decreased growth due to delayed G1-to-S cell-cycle transition. Lack of Par-4 also increased the expression of p21 and delayed CLL growth in Eμ-Tcl1 mice. Par-4 expression in CLL cells required constitutively active B-cell receptor (BCR) signaling, as inhibition of BCR signaling with US Food and Drug Administration (FDA)-approved drugs caused a decrease in Par-4 messenger RNA and protein, and an increase in apoptosis. In particular, activities of Lyn, a Src family kinase, spleen tyrosine kinase, and Bruton tyrosine kinase are required for Par-4 expression in CLL cells, suggesting a novel regulation of Par-4 through BCR signaling. Together, these results suggest that Par-4 may play a novel progrowth rather than proapoptotic role in CLL and could be targeted to enhance the therapeutic effects of BCR-signaling inhibitors.