PEA-15 facilitates EGFR dephosphorylationviaERK sequestration at increased ER-PM contacts in TNBC cells

Transcription Factor FOSL1 Enhances Drug Resistance of Breast Cancer Through DUSP7-Mediated Dephosphorylation of PEA15

Breast cancer (BC) represents one of the commonest and deadliest malignancies in women. However, drug resistance has always been a major obstacle to cancer treatment. Transcription factors have been reported to have close association with drug resistance of tumors. Recently, by analyzing the data from Gene Expression Omnibus (GEO) database (id: GSE76540), we found that transcription factor FOSL1 was significantly up-regulated in the transcriptome of doxorubicin-resistant BC cells compared with that in sensitive parental cells. Therefore, we aim to explore the regulatory mechanism of FOSL1 in affecting the drug resistance of BC cells. FOSL1 expression in doxorubicin-resistant BC cells was firstly examined through RT-qPCR, and then its influence on the drug resistance of BC cells was explored through a series of in vitro and in vivo mechanism assays. Results showed that FOSL1 promoted the drug resistance of BC cells to doxorubicin both in intro and in vivo. It positively regulated the transcription of DUSP7 in BC doxorubicin-resistant cells and DUSP7 also enhanced the drug resistance of BC cells. Furthermore, FOSL1 promoted the dephosphorylation of PEA15 through DUSP7. In conclusion, it was verified that FOSL1 promoted the drug resistance in breast cancer through DUSP7-mediated dephosphorylation of PEA15. Implications: These initial findings suggest that the FOSL1/DUSP7/PEA15 pathway may provide a theoretical guidance for BC treatment.

Nonphosphorylatable PEA15 mutant inhibits epithelial-mesenchymal transition in triple-negative breast cancer partly through the regulation of IL-8 expression

Background

Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype that lacks targeted therapies. Patients with TNBC have a very poor prognosis because the disease often metastasizes. New treatment approaches addressing drivers of metastasis and tumor growth are crucial to improving patient outcomes. Developing targeted gene therapy is thus a high priority for TNBC patients. PEA15 (phosphoprotein enriched in astrocytes, 15 kDa) is known to bind to ERK, preventing ERK from being translocated to the nucleus and hence blocking its activity. The biological function of PEA15 is tightly regulated by its phosphorylation at Ser104 and Ser116. However, the function and impact of phosphorylation status of PEA15 in the regulation of TNBC metastasis and in epithelial-to-mesenchymal transition (EMT) are not well understood.

Methods

We established stable cell lines overexpressing nonphosphorylatable (PEA15-AA) and phospho-mimetic (PEA15-DD) mutants. To dissect specific cellular mechanisms regulated by PEA15 phosphorylation status, we performed RT-PCR immune and metastasis arrays. In vivo mouse models were used to determine the effects of PEA15 phosphorylation on tumor growth and metastasis.

Results

We found that the nonphosphorylatable mutant PEA15-AA prevented formation of mammospheres and expression of EMT markers in vitro and decreased tumor growth and lung metastasis in in vivo experiments when compared to control, PEA15-WT and phosphomimetic PEA15-DD. However, phosphomimetic mutant PEA15-DD promoted migration, mesenchymal marker expression, tumorigenesis, and lung metastasis in the mouse model. PEA15-AA-mediated inhibition of breast cancer cell migratory capacity and tumorigenesis was the partial result of decreased expression of interleukin-8 (IL-8). Further, we identified that expression of IL-8 was possibly mediated through one of the ERK downstream molecules, Ets-1.

Conclusions

Our results show that PEA15 phosphorylation status serves as an important regulator for PEA15’s dual role as an oncogene or tumor suppressor and support the potential of PEA15-AA as a therapeutic strategy for treatment of TNBC.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10549-021-06316-2.

Phosphorylation of PED/PEA-15 at Ser116 and phosphorylation of p27 at Thr187 indicates a poor prognosis in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) constitutes a deadly cancer with a high rate of recurrence and metastasis. Phosphoprotein enriched in diabetes/phosphoprotein enriched in astrocytes-15 (PED/PEA-15) is a protein involved in the metabolism of glucose that regulates numerous cellular processes, including cell division, apoptosis and migration in numerous types of cancer. However, PED/PEA-15 may act as a tumor-promotor or a tumor-suppressor depending on its phosphorylation status. In the present study, the association between the phosphorylation of PED/PEA-15 at Ser116 [PED/PEA-15(S116)], the phosphorylation of P27 at Thr187 [P-p27(T187)] and the clinicopathological features and prognosis of patients with HCC was assessed. The levels of PED/PEA-15(S116) and P-p27(T187) were determined using immunohistochemistry and western blotting analysis in resected liver tumor tissues and adjacent non-cancerous tissues obtained from 60 patients with HCC as well as normal liver tissues from 12 patients with benign lesions. The association between the expression levels of these two markers and the clinicopathological features of patients with HCC was explored. Using the Kaplan-Meier method, the prognostic value of PED/PEA-15(S116) and P-p27(T187) expression levels was determined. The results demonstrated that the levels of PED/PEA-15(S116) and P-p27(T187) proteins were remarkably higher in the HCC group compared with those in the adjacent and normal tissue groups (both P<0.05). In addition, a moderate positive correlation was observed between the levels of PED/PEA-15(S116) and P-p27(T187) (r=0.434; P<0.05). The levels of these two proteins were associated with the Edmondson grade, Tumor-Node-Metastasis (TNM) stage, vascular invasion and tumor multiplicity (all P<0.05). Furthermore, the Kaplan-Meier analysis results demonstrated that patients with HCC that presented with positive expression of PED/PEA-15(S116) and P-p27(T187) exhibited a dismal prognosis compared with that in patients with negative expression regarding the overall survival (OS), as well as disease-free survival (both P<0.05). Multivariate Cox analysis revealed that the TNM stage (P<0.05), vascular invasion (P<0.05), PED/PEA-15(S116) levels (P<0.001) and P-p27(T187) levels (P<0.05) were independent prognostic factors for OS in patients with HCC. In conclusion the results of the present study demonstrated that PED/PEA-15(S116) and P-p27(T187) levels were upregulated in HCC tissues compared with those in the adjacent and normal tissues; PED/PEA-15(S116) and P-p27(T187) expression may serve as an indicator of a poor prognosis in patients with HCC, suggesting that these proteins may be prospective therapeutic targets for HCC.

Analysis of CRISPR-Cas9 screens identifies genetic dependencies in melanoma

Targeting the MAPK signaling pathway has transformed the treatment of metastatic melanoma. CRISPR-Cas9 genetic screens provide a genome-wide approach to uncover novel genetic dependencies that might serve as therapeutic targets. Here, we analyzed recently reported CRISPR-Cas9 screens comparing data from 28 melanoma cell lines and 313 cell lines of other tumor types in order to identify fitness genes related to melanoma. We found an average of 1,494 fitness genes in each melanoma cell line. We identified 33 genes, inactivation of which specifically reduced the fitness of melanoma. This set of tumor type-specific genes includes established melanoma fitness genes as well as many genes that have not previously been associated with melanoma growth. Several genes encode proteins that can be targeted using available inhibitors. We verified that genetic inactivation of DUSP4 and PPP2R2A reduces the proliferation of melanoma cells. DUSP4 encodes an inhibitor of ERK, suggesting that further activation of MAPK signaling activity through its loss is selectively deleterious to melanoma cells. Collectively, these data present a resource of genetic dependencies in melanoma that may be explored as potential therapeutic targets.

The microRNA212 regulated PEA15 promotes ovarian cancer progression by inhibiting of apoptosis

PEA15 (Proliferation And Apoptosis Adaptor) is a 15kDa multifunctional phosphoprotein involved in various essential biological processes such as proliferation and apoptosis of cancer cells. Previous studies have demonstrated that PEA15 can promote the progression of many malignancies. In the present study, the expression of PEA15 in ovarian cancer and normal tissues analyzed in several databases and PEA15 was found to be significantly up-regulated in OC tissues compared to normal tissues. Immunochemical assays performed using 171 OC tissue specimens proved that the expression of PEA15 was remarkably positively correlated with the FIGO stage and associated with histologic subgroups of ovarian cancer. IHC assay for the two phosphorylation sites of PEA15 S116 and S104 was also performed. PEA15 high expression predicted a poor prognosis in OC patients analysed from K-M plot dataset. In addition, we proved knockdown of PEA15 inhibits OC cell proliferation and induces cell apoptosis by Bcl2 downregulation and Bax and cleaved Caspase-3 upregulation. Overexpression of PEA15 promotes the proliferative capacity of OC cells. Moreover, this study first discovered PEA15 expression in OC can be negatively regulated by microRNA212. Overexpression of miR-212 in ovarian cancer cells could cause downregulated the expression of PEA15 expression. Overexpression of miR-212 was found to exerted similar effects on the proliferation, and apoptosis of the ovarian cancer cells as that of PEA15 suppression. Additionally, overexpression of PEA15could at least partially abolished the effects of miR-212 on the proliferation, and apoptosis of ovarian cancer cells. In conclusion, our findings revealed PEA15 appears as a novel predictive biomarker, thus providing a valuable therapeutic target in OC treatment strategy.

PEA15 promotes liver metastasis of colorectal cancer by upregulating the ERK/MAPK signaling pathway

Liver metastasis is one of the major causes of death in patients with colorectal cancer, and although treatment has improved recently, the long‑term survival rate of patients has not improved significantly. In the present study, we used immunohistochemistry to determine that phosphoprotein enriched in astrocytes‑15 kDa (PEA15) was highly expressed in colorectal cancer tissues and liver metastatic cancer tissues. It was also highly expressed in metastatic colorectal cancer patients compared to non‑metastatic patients. Through clinicopathological data of patients with liver metastasis of colorectal cancer, we found that high expression of PEA15 was positively correlated with TNM staging, liver metastasis and poor prognosis of colorectal cancer patients. Using confocal immunofluorescence microscopy, western blotting and cell proliferation, migration and invasion assays, we also determined that PEA15 could promote cancer cell proliferation in vitro and in vivo, epithelial mesenchymal transition (EMT) and the characteristics of cancer stem cells in vitro, thus promoting the abilities of invasion and migration. In addition, we revealed that PEA15 promoted the liver metastasis of colorectal cancer cells in a xenograft tumor metastasis model. In addition, concerning the mechanism, we used gene chip analysis to determine that PEA15 upregulated the ERK/MAPK signaling pathway in colorectal cancer cells. Therefore, we concluded that PEA15 may be a potential biomarker for liver metastasis of colorectal cancer therapy. Collectively, PEA15 promoted the development of liver metastasis of colorectal cancer through the ERK/MAPK signaling pathway.

Phosphoprotein enriched in diabetes (PED/PEA15) promotes migration in hepatocellular carcinoma and confers resistance to sorafenib

Hepatocellular carcinoma (HCC) is the third-leading cause of cancer-related death with limited treatment options and frequent resistance to sorafenib, the only drug currently approved for first-line therapy. Therefore, better understanding of HCC tumor biology and its resistance to treatment is urgently needed. Here, we analyzed the role of phosphoprotein enriched in diabetes (PED) in HCC. PED has been shown to regulate cell proliferation, apoptosis and migration in several types of cancer. However, its function in HCC has not been addressed yet. Our study revealed that both transcript and protein levels of PED were significantly high in HCC compared with non-tumoral tissue. Clinico-pathological correlation revealed that PED^high HCCs showed an enrichment of gene signatures associated with metastasis and poor prognosis. Further, we observed that PED overexpression elevated the migration potential and PED silencing the decreased migration potential in liver cancer cell lines without effecting cell proliferation. Interestingly, we found that PED expression was regulated by a hepatocyte specific nuclear factor, HNF4α. A reduction of HNF4α induced an increase in PED expression and consequently, promoted cell migration in vitro. Finally, PED reduced the antitumoral effect of sorafenib by inhibiting caspase-3/7 activity. In conclusion, our data suggest that PED has a prominent role in HCC biology. It acts particularly on promoting cell migration and confers resistance to sorafenib treatment. PED may be a novel target for HCC therapy and serve as a predictive marker for treatment response against sorafenib.

Next-Generation CDK2/9 Inhibitors and Anaphase Catastrophe in Lung Cancer

Background

The first generation CDK2/7/9 inhibitor seliciclib (CYC202) causes multipolar anaphase and apoptosis in lung cancer cells with supernumerary centrosomes (known as anaphase catastrophe). We investigated a new and potent CDK2/9 inhibitor, CCT68127 (Cyclacel).

Methods

CCT68127 was studied in lung cancer cells (three murine and five human) and control murine pulmonary epithelial and human immortalized bronchial epithelial cells. Robotic CCT68127 cell-based proliferation screens were used. Cells undergoing multipolar anaphase and inhibited centrosome clustering were scored. Reverse phase protein arrays (RPPAs) assessed CCT68127 effects on signaling pathways. The function of PEA15, a growth regulator highlighted by RPPAs, was analyzed. Syngeneic murine lung cancer xenografts (n = 4/group) determined CCT68127 effects on tumorigenicity and circulating tumor cell levels. All statistical tests were two-sided.

Results

CCT68127 inhibited growth up to 88.5% (SD = 6.4%, P < .003) at 1 μM, induced apoptosis up to 42.6% (SD = 5.5%, P < .001) at 2 μM, and caused G1 or G2/M arrest in lung cancer cells with minimal effects on control cells (growth inhibition at 1 μM: 10.6%, SD = 3.6%, P = .32; apoptosis at 2 μM: 8.2%, SD = 1.0%, P = .22). A robotic screen found that lung cancer cells with KRAS mutation were particularly sensitive to CCT68127 ( P = .02 for IC 50 ). CCT68127 inhibited supernumerary centrosome clustering and caused anaphase catastrophe by 14.1% (SD = 3.6%, P < .009 at 1 μM). CCT68127 reduced PEA15 phosphorylation by 70% (SD = 3.0%, P = .003). The gain of PEA15 expression antagonized and its loss enhanced CCT68127-mediated growth inhibition. CCT68127 reduced lung cancer growth in vivo ( P < .001) and circulating tumor cells ( P = .004). Findings were confirmed with another CDK2/9 inhibitor, CYC065.

Conclusions

Next-generation CDK2/9 inhibition elicits marked antineoplastic effects in lung cancer via anaphase catastrophe and reduced PEA15 phosphorylation.

Targetting PED/PEA-15 for diabetes treatment

INTRODUCTION

PED/PEA-15 is an ubiquitously expressed protein, involved in the regulation of proliferation and apoptosis. It is commonly overexpressed in Type 2 Diabetes (T2D) and in different T2D-associated comorbidities, including cancer and certain neurodegenerative disorders. Areas covered: In mice, Ped/Pea-15 overexpression impairs glucose tolerance and, in combination with high fat diets, further promotes insulin resistance and T2D. It also controls β-cell mass, altering caspase-3 activation and the expression of pro- and antiapoptotic genes. These changes are mediated by PED/PEA-15-PLD1 binding. Overexpression of PLD1 D4 domain specifically blocks Ped/Pea-15-PLD1 interaction, reverting the effect of Ped/Pea-15 in vivo. D4α, a D4 N-terminal peptide, is able to displace Ped/Pea-15-PLD1 binding, but features greater stability in vivo compared to the entire D4 peptide. Here, we review early mechanistic studies on PED/PEA-15 relevance in apoptosis before focusing on its role in cancer and T2D. Finally, we describe potential therapeutic opportunities for T2D based on PED/PEA-15 targeting. Expert opinion: T2D is a major problem for public health and economy. Thus, the identification of new molecules with pharmacological activity for T2D represents an urgent need. Further studies with D4α will help to identify smaller pharmacologically active peptides and innovative molecules of potential pharmacological interest for T2D treatment.

Multivesicular body formation enhancement and exosome release during endoplasmic reticulum stress

The endoplasmic reticulum (ER) plays a pivotal role in maintaining cellular homeostasis. However, numerous environmental and genetic factors give rise to ER stress by inducing an accumulation of unfolded proteins. Under ER stress conditions, cells initiate the unfolded protein response (UPR). Here, we demonstrate a novel aspect of the UPR by electron microscopy and immunostaining analyses, whereby multivesicular body (MVB) formation was enhanced after ER stress. This MVB formation was influenced by inhibition of ER stress transducers inositol required enzyme 1 (IRE1) and PKR-like ER kinase (PERK). Furthermore, exosome release was also increased during ER stress. However, in IRE1 or PERK deficient cells, exosome release was not upregulated, indicating that IRE1- and PERK-mediated pathways are involved in ER stress-dependent exosome release.

On the Quest of Cellular Functions of PEA-15 and the Therapeutic Opportunities

Phosphoprotein enriched in astrocytes, 15 KDa (PEA-15), a ubiquitously expressed small protein in all mammals, is known for decades for its potent interactions with various protein partners along distinct biological pathways. Most notable interacting partners of PEA-15 include extracellular signal-regulated kinase 1 and 2 (ERK1/2) in the mitogen activated protein kinase (MAPK) pathway, the Fas-associated death domain (FADD) protein involving in the formation of the death-inducing signaling complex (DISC), and the phospholipase D1 (PLD1) affecting the insulin sensitivity. However, the actual cellular functions of PEA-15 are still mysterious, and the question why this protein is expressed in almost all cell and tissue types remains unanswered. Here we synthesize the most recent structural, biological, and clinical studies on PEA-15 with emphases on its anti-apoptotic, anti-proliferative, and anti-inflammative properties, and propose a converged protective role of PEA-15 that maintains the balance of death and survival in different cell types. Under conditions that this delicate balance is unsustainable, PEA-15 may become pathological and lead to various diseases, including cancers and diabetes. Targeting PEA-15 interactions, or the use of PEA-15 protein as therapeutics, may provide a wider window of opportunities to treat these diseases.