DARPP-32 and t-DARPP promote non-small cell lung cancer growth through regulation of IKKα-dependent cell migration

Evaluation of t-DARPP Expression Alteration in Association with DDR1 Expression in Non-Small Cell Lung Cancer

Background

Discoidin domain receptor 1 (DDR1) signaling plays a critical role in various cellular functions. Increased DDR1 expression has been shown in different human cancers. t-DARPP is a truncated isoform of DARPP-32, and its upregulation promotes cell survival and migration. Most lung cancer patients have non-small cell lung cancer (NSCLC), and their survival rate is low. Therefore, it is necessary to study new and effective targeted therapies. Increased t-DARPP expression in NSCLC patients is associated with patient survival and can act as a prognostic marker correlated with increasing stages of NSCLC. The current study aimed to evaluate alteration in DDR1 expression and its effects on t-DARPP expression in NSCLC.

Methods

Two human lung adenocarcinoma cell lines, A549 and Calu-3, were treated with collagen type I and transfected with DDR1 siRNA. The relative expression of DDR1 and t-DARPP was evaluated using qRT-PCR.

Results

The results indicated that collagen type I could stimulate DDR1 expression in NSCLC cells. Also, DDR1 upregulation resulted in a significant increase in t-DARPP expression. In contrast, suppression of DDR1 expression significantly decreased t-DARPP expression.

Conclusion

Our findings propose that modification in the expression of DDR1, caused by collagen type I and siRNA, might influence the expression of t-DARPP in NSCLC that is linked to NSCLC progression. Moreover, this alteration could potentially serve as an innovative target for therapeutic intervention.

Unravelling transcriptomic complexity in breast cancer through modulation of DARPP-32 expression and signalling pathways

DARPP-32 is a key regulator of protein-phosphatase-1 (PP-1) and protein kinase A (PKA), with its function dependent upon its phosphorylation state. We previously identified DKK1 and GRB7 as genes with linked expression using Artificial Neural Network (ANN) analysis; here, we determine protein expression in a large cohort of early-stage breast cancer patients. Low levels of DARPP-32 Threonine-34 phosphorylation and DKK1 expression were significantly associated with poor patient prognosis, while low levels of GRB7 expression were linked to better survival outcomes. To gain insight into mechanisms underlying these associations, we analysed the transcriptome of T47D breast cancer cells following DARPP-32 knockdown. We identified 202 differentially expressed transcripts and observed that some overlapped with genes implicated in the ANN analysis, including PTK7, TRAF5, and KLK6, amongst others. Furthermore, we found that treatment of DARPP-32 knockdown cells with 17β-estradiol or PKA inhibitor fragment (6-22) amide led to the differential expression of 193 and 181 transcripts respectively. These results underscore the importance of DARPP-32, a central molecular switch, and its downstream targets, DKK1 and GRB7 in breast cancer. The discovery of common genes identified by a combined patient/cell line transcriptomic approach provides insights into the molecular mechanisms underlying differential breast cancer prognosis and highlights potential targets for therapeutic intervention.

Dopamine and cyclic adenosine monophosphate-regulated phosphoprotein with an apparent Mr of 32000 promotes colorectal cancer growth

BACKGROUND

Dopamine and cyclic adenosine monophosphate (cAMP)-regulated phosphoprotein with an apparent Mr of 32000 (DARPP-32) is a protein that is involved in regulating dopamine and cAMP signaling pathways in the brain. However, recent studies have shown that DARPP-32 is also expressed in other tissues, including colorectal cancer (CRC), where its function is not well understood.

AIM

To explore the effect of DARPP-32 on CRC progression.

METHODS

The expression levels of DARPP-32 were assessed in CRC tissues using both quantitative polymerase chain reaction and immunohistochemistry assays. The proliferative capacity of CRC cell lines was evaluated with Cell Counting Kit-8 and 5-ethynyl-2’-deoxyuridine assays, while apoptosis was measured by flow cytometry. The migratory and invasive potential of CRC cell lines were determined using wound healing and transwell chamber assays. In vivo studies involved monitoring the growth rate of xenograft tumors. Finally, the underlying molecular mechanism of DARPP-32 was investigated through RNA-sequencing and western blot analyses.

RESULTS

DARPP-32 was frequently upregulated in CRC and associated with abnormal clinicopathological features in CRC. Overexpression of DARPP-32 was shown to promote cancer cell proliferation, migration, and invasion and reduce apoptosis. DARPP-32 knockdown resulted in the opposite functional effects. Mechanistically, DARPP-32 may regulate the phosphoinositide 3-kinase (PI3K)/AKT signaling pathway in order to carry out its biological function.

CONCLUSION

DARPP-32 promotes CRC progression via the PI3K/AKT signaling pathway.

IKKα promotes lung adenocarcinoma growth through ERK signaling activation via DARPP-32-mediated inhibition of PP1 activity

Non-small cell lung cancer (NSCLC) accounts for 80-85% cases of lung cancer cases. Diagnosis at advanced stages is common, after which therapy-refractory disease progression frequently occurs. Therefore, a better understanding of the molecular mechanisms that control NSCLC progression is necessary to develop new therapies. Overexpression of IκB kinase α (IKKα) in NSCLC correlates with poor patient survival. IKKα is an NF-κB-activating kinase that is important in cell survival and differentiation, but its regulation of oncogenic signaling is not well understood. We recently demonstrated that IKKα promotes NSCLC cell migration by physically interacting with dopamine- and cyclic AMP-regulated phosphoprotein, Mr 32000 (DARPP-32), and its truncated splice variant, t-DARPP. Here, we show that IKKα phosphorylates DARPP-32 at threonine 34, resulting in DARPP-32-mediated inhibition of protein phosphatase 1 (PP1), subsequent inhibition of PP1-mediated dephosphorylation of ERK, and activation of ERK signaling to promote lung oncogenesis. Correspondingly, IKKα ablation in human lung adenocarcinoma cells reduced their anchorage-independent growth in soft agar. Mice challenged with IKKα-ablated HCC827 cells exhibited less lung tumor growth than mice orthotopically administered control HCC827 cells. Our findings suggest that IKKα drives NSCLC growth through the activation of ERK signaling via DARPP-32-mediated inhibition of PP1 activity.

IKKα Induces Epithelial–Mesenchymal Changes in Mouse Skin Carcinoma Cells That Can Be Partially Reversed by Apigenin

NMSC (non-melanoma skin cancer) is a common tumor in the Caucasian population, accounting for 90% of skin cancers. Among them, squamous cell carcinomas (SCCs) can metastasize and, due to its high incidence, constitute a severe health problem. It has been suggested that cutaneous SCCs with more risk to metastasize express high levels of nuclear IKKα. However, the molecular mechanisms that lead to this enhanced aggressiveness are largely unknown. To understand in depth the influence of nuclear IKKα in skin SCC progression, we have generated murine PDVC57 skin carcinoma cells expressing exogenous IKKα either in the nucleus or in the cytoplasm to further distinguish the tumor properties of IKKα in both localizations. Our results show that IKKα promotes changes in both subcellular compartments, resembling EMT (epithelial–mesenchymal transition), which are more pronounced when IKKα is in the nucleus of these tumor cells. These EMT-related changes include a shift toward a migratory phenotype and induction of the expression of proteins involved in cell matrix degradation, cell survival and resistance to apoptosis. Additionally, we have found that apigenin, a flavonoid with anti-cancer properties, inhibits the expression of IKKα and attenuates most of the pro-tumoral EMT changes induced by IKKα in mouse tumor keratinocytes. Nevertheless, we have found that apigenin only inhibits the expression of the IKKα protein when it is localized in the cytoplasm.

DARPP-32 promotes ERBB3-mediated resistance to molecular targeted therapy in EGFR-mutated lung adenocarcinoma

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI)-refractory lung adenocarcinoma (LUAD) progression is a major clinical problem. New approaches to predict and prevent acquired resistance to EGFR TKIs are urgently needed. Here, we show that dopamine and cyclic AMP-regulated phosphoprotein, Mr 32000 (DARPP-32) physically recruits ERBB3 (HER3) to EGFR to mediate switching from EGFR homodimers to EGFR:ERBB3 heterodimers to bypass EGFR TKI-mediated inhibition by potentiating ERBB3-dependent activation of oncogenic signaling. In paired LUAD patient-derived specimens before and after EGFR TKI-refractory disease progression, we reveal that DARPP-32 and kinase-activated EGFR and ERBB3 proteins are overexpressed upon acquired resistance. In mice, DARPP-32 ablation sensitizes gefitinib-resistant xenografts to EGFR TKIs, while DARPP-32 overexpression increases gefitinib-refractory LUAD progression in gefitinib-sensitive lung tumors. We introduce a DARPP-32-mediated, ERBB3-dependent mechanism the LUAD cells use to evade EGFR TKI-induced cell death, potentially paving the way for the development of therapies to better combat therapy-refractory LUAD progression.

Vascular Endothelial Growth Factor as an Immediate-Early Activator of Ultraviolet-Induced Skin Injury

The negative health consequences of acute ultraviolet (UV) exposure are evident, with reports of 30,000 emergency room visits annually to treat the effects of sunburn in the United States alone. The acute effects of sunburn include erythema, edema, severe pain, and chronic overexposure to UV radiation, leading to skin cancer. Whereas the pain associated with the acute effects of sunburn may be relieved by current interventions, existing post-sunburn treatments are not capable of reversing the cumulative and long-term pathological effects of UV exposure, an unmet clinical need. Here we show that activation of the vascular endothelial growth factor (VEGF) pathway is a direct and immediate consequence of acute UV exposure, and activation of VEGF signaling is necessary for initiating the acute pathological effects of sunburn. In UV-exposed human subjects, VEGF signaling is activated within hours. Topical delivery of VEGF pathway inhibitors, targeted against the ligand VEGF-A (gold nanoparticles conjugated with anti-VEGF antibodies) and small-molecule antagonists of VEGF receptor signaling, prevent the development of erythema and edema in UV-exposed mice. These findings collectively suggest targeting VEGF signaling may reduce the subsequent inflammation and pathology associated with UV-induced skin damage, revealing a new postexposure therapeutic window to potentially inhibit the known detrimental effects of UV on human skin. It is essential to emphasize that these preclinical studies must not be construed as suggesting in any way the use of VEGF inhibitors as a sunburn treatment in humans because warranted future clinical studies and appropriate agency approval are essential in that regard.

Suppressing STAT3 activity protects the endothelial barrier from VEGF-mediated vascular permeability

Vascular permeability triggered by inflammation or ischemia promotes edema, exacerbates disease progression and impairs tissue recovery. Vascular endothelial growth factor (VEGF) is a potent inducer of vascular permeability. VEGF plays an integral role in regulating vascular barrier function physiologically and in pathologies, including cancer, stroke, cardiovascular disease, retinal conditions and COVID-19-associated pulmonary edema, sepsis and acute lung injury. Understanding temporal molecular regulation of VEGF-induced vascular permeability will facilitate developing therapeutics to inhibit vascular permeability, while preserving tissue-restorative angiogenesis. Here, we demonstrate that VEGF signals through signal transducer and activator of transcription 3 (STAT3) to promote vascular permeability. We show that genetic STAT3 ablation reduces vascular permeability in STAT3-deficient endothelium of mice and VEGF-inducible zebrafish crossed with CRISPR/Cas9-generated Stat3 knockout zebrafish. Intercellular adhesion molecule 1 (ICAM-1) expression is transcriptionally regulated by STAT3, and VEGF-dependent STAT3 activation is regulated by JAK2. Pyrimethamine, an FDA-approved antimicrobial agent that inhibits STAT3-dependent transcription, substantially reduces VEGF-induced vascular permeability in zebrafish, mouse and human endothelium. Collectively, our findings suggest that VEGF/VEGFR-2/JAK2/STAT3 signaling regulates vascular barrier integrity, and inhibition of STAT3-dependent activity reduces VEGF-induced vascular permeability.

This article has an associated First Person interview with the first author of the paper.

Summary: Genetic STAT3 ablation in mice and VEGF-inducible zebrafish reveals that VEGF signals through STAT3 to promote vascular permeability. Pyrimethamine reduces VEGF-induced permeability in animal models.

PP1, PKA and DARPP-32 in breast cancer: A retrospective assessment of protein and mRNA expression

Cyclic AMP–dependent protein kinase A (PKA) and protein phosphatase 1 (PP1) are proteins involved in numerous essential signalling pathways that modulate physiological and pathological functions. Both PP1 and PKA can be inhibited by dopamine‐ and cAMP‐regulated phosphoprotein 32 kD (DARPP‐32). Using immunohistochemistry, PKA and PP1 expression was determined in a large primary breast tumour cohort to evaluate associations between clinical outcome and clinicopathological criteria (n > 1100). In addition, mRNA expression of PKA and PP1 subunits was assessed in the METABRIC data set (n = 1980). Low protein expression of PKA was significantly associated with adverse survival of breast cancer patients; interestingly, this relationship was stronger in ER‐positive breast cancer patients. PP1 protein expression was not associated with patient survival. PKA and PP1 subunit mRNA was also assessed; PPP1CA, PRKACG and PRKAR1B were associated with breast cancer–specific survival. In patients with high expression of DARPP‐32, low expression of PP1 was associated with adverse survival when compared to high expression in the same group. PKA expression and PP1 expression are of significant interest in cancer as they are involved in a wide array of cellular processes, and these data indicate PKA and PP1 may play an important role in patient outcome.

Suppressing STAT3 activity protects the endothelial barrier from VEGF-mediated vascular permeability

Vascular permeability triggered by inflammation or ischemia promotes edema, exacerbates disease progression, and impairs tissue recovery. Vascular endothelial growth factor (VEGF) is a potent inducer of vascular permeability. VEGF plays an integral role in regulating vascular barrier function physiologically and in pathologies, such as cancer, ischemic stroke, cardiovascular disease, retinal conditions, and COVID-19-associated pulmonary edema and sepsis, which often leads to acute lung injury, including acute respiratory distress syndrome. However, after initially stimulating permeability, VEGF subsequently mediates angiogenesis to repair damaged tissue. Consequently, understanding temporal molecular regulation of VEG-Finduced vascular permeability will facilitate developing therapeutics that achieve the delicate balance of inhibiting vascular permeability while preserving tissue repair. Here, we demonstrate that VEGF signals through signal transducer and activator of transcription 3 (STAT3) to promote vascular permeability. Specifically, we show that genetic STAT3 ablation reduces vascular permeability in STAT3-deficient endothelium of mice and VEGF-inducible zebrafish crossed with CRISPR/Cas9 generated genomic STAT3 knockout zebrafish. Importantly, STAT3 deficiency does not impair vascular development and function in vivo. We identify intercellular adhesion molecule 1 (ICAM-1) as a STAT3-dependent transcriptional regulator and show VEGF-dependent STAT3 activation is regulated by JAK2. Pyrimethamine, an FDA-approved antimicrobial agent that inhibits STAT3-dependent transcription, substantially reduces VEGF-induced vascular permeability in zebrafish, mouse, and human endothelium. Indeed, pharmacologically targeting STAT3 increases vascular barrier integrity using two additional compounds, atovaquone and C188-9. Collectively, our findings suggest that the VEGF, VEGFR-2, JAK2, and STAT3 signaling cascade regulates vascular barrier integrity, and inhibition of STAT3-dependent activity reduces VEGF-induced vascular permeability in vertebrate models.

Dopamine D1 Receptor in Cancer

Simple Summary

Circulating hormones and their specific receptors play a significant role in the development and progression of various cancers. This review aimed to summarize current knowledge about the dopamine D1 receptor’s biological role in different cancers, including breast cancer, central nervous system tumors, lymphoproliferative disorders, and other neoplasms. Treatment with dopamine D1 receptor agonists was proven to exert a major anti-cancer effect in many preclinical models. We highlight this receptor’s potential as a target for the adjunct therapy of tumors and discuss possibilities and necessities for further research in this area.

Abstract

Dopamine is a biologically active compound belonging to catecholamines. It plays its roles in the human body, acting both as a circulating hormone and neurotransmitter. It acts through G-protein-coupled receptors divided into two subgroups: D1-like receptors (D1R and D5R) and D2-like receptors (D2R, D3R, D4R). Physiologically, dopamine receptors are involved in central nervous system functions: motivation or cognition, and peripheral actions such as blood pressure and immune response modulation. Increasing evidence indicates that the dopamine D1 receptor may play a significant role in developing different human neoplasms. This receptor’s value was presented in the context of regulating various signaling pathways important in tumor development, including neoplastic cell proliferation, apoptosis, autophagy, migration, invasiveness, or the enrichment of cancer stem cells population. Recent studies proved that its activation by selective or non-selective agonists is associated with significant tumor growth suppression, metastases prevention, and tumor microvasculature maturation. It may also exert a synergistic anti-cancer effect when combined with tyrosine kinase inhibitors or temozolomide. This review provides a comprehensive insight into the heterogeneity of dopamine D1 receptor molecular roles and signaling pathways in human neoplasm development and discusses possible perspectives of its therapeutic targeting as an adjunct anti-cancer strategy of treatment. We highlight the priorities for further directions in this research area.

Loss of HIF1A From Pancreatic Cancer Cells Increases Expression of PPP1R1B and Degradation of p53 to Promote Invasion and Metastasis

BACKGROUND & AIMS

Pancreatic ductal adenocarcinomas (PDACs) are hypovascular, resulting in the up-regulation of hypoxia inducible factor 1 alpha (HIF1A), which promotes the survival of cells under low-oxygen conditions. We studied the roles of HIF1A in the development of pancreatic tumors in mice.

METHODS

We performed studies with Kras^LSL-G12D/+;Trp53^LSL-R172H/+;Pdx1-Cre (KPC) mice, KPC mice with labeled pancreatic epithelial cells (EKPC), and EKPC mice with pancreas-specific depletion of HIF1A. Pancreatic and other tissues were collected and analyzed by histology and immunohistochemistry. Cancer cells were cultured from PDACs from mice and analyzed in cell migration and invasion assays and by immunoblots, real-time polymerase chain reaction, and liquid chromatography-mass spectrometry. We performed studies with the human pancreatic cancer cell lines PATU-8988T, BxPC-3, PANC-1, and MiaPACA-2, which have no or low metastatic activity, and PATU-8988S, AsPC-1, SUIT-2 and Capan-1, which have high metastatic activity. Expression of genes was knocked down in primary cancer cells and pancreatic cancer cell lines by using small hairpin RNAs; cells were injected intravenously into immune-competent and NOD/SCID mice, and lung metastases were quantified. We compared levels of messenger RNAs in pancreatic tumors and normal pancreas in The Cancer Genome Atlas.

RESULTS

EKPC mice with pancreas-specific deletion of HIF1A developed more advanced pancreatic neoplasias and PDACs with more invasion and metastasis, and had significantly shorter survival times, than EKPC mice. Pancreatic cancer cells from these tumors had higher invasive and metastatic activity in culture than cells from tumors of EKPC mice. HIF1A-knockout pancreatic cancer cells had increased expression of protein phosphatase 1 regulatory inhibitor subunit 1B (PPP1R1B). There was an inverse correlation between levels of HIF1A and PPP1R1B in human PDAC tumors; higher expression of PPP1R1B correlated with shorter survival times of patients. Metastatic human pancreatic cancer cell lines had increased levels of PPP1R1B and lower levels of HIF1A compared with nonmetastatic cancer cell lines; knockdown of PPP1R1B significantly reduced the ability of pancreatic cancer cells to form lung metastases in mice. PPP1R1B promoted degradation of p53 by stabilizing phosphorylation of MDM2 at Ser166.

CONCLUSIONS

HIF1A can act a tumor suppressor by preventing the expression of PPP1R1B and subsequent degradation of the p53 protein in pancreatic cancer cells. Loss of HIF1A from pancreatic cancer cells increases their invasive and metastatic activity.

Dopamine and cAMP-regulated phosphoprotein 32kDa (DARPP-32), protein phosphatase-1 and cyclin-dependent kinase 5 expression in ovarian cancer

Dopamine and cyclic‐AMP activated phosphoprotein Mr32kDa (DARPP‐32) is a central signalling protein in neurotransmission. Following DARPP‐32 phosphorylation by protein kinase A (PKA), DARPP‐32 becomes a potent protein phosphatase 1 (PP1) inhibitor. DARPP‐32 can itself inhibit PKA following DARPP‐32 phosphorylation by cyclin‐dependent kinase 5 (Cdk5). Increasing evidence indicates a role for DARPP‐32 and its associated signalling pathways in cancer; however, its role in ovarian cancer remains unclear. Using immunohistochemistry, expression of DARPP‐32, PP1 and Cdk5 was determined in a large cohort of primary tumours from ovarian cancer patients (n = 428, 445 and 434 respectively) to evaluate associations between clinical outcome and clinicopathological criteria. Low cytoplasmic and nuclear DARPP‐32 expression was associated with shorter patient overall survival and progression‐free survival (P = .001, .001, .004 and .037 respectively). Low nuclear and cytoplasmic DARPP‐32 expression remained significantly associated with overall survival in multivariate Cox regression (P = .045, hazard ratio (HR) = 0.734, 95% confidence interval (CI) = 0.542‐0.993 and P = .001, HR = 0.494, 95% CI = 0.325‐0.749, respectively). High cytoplasmic and nuclear PP1 expression was associated with shorter patient overall survival and high cytoplasmic PP1 expression with shorter progression‐free survival (P = .005, .033, and .037, respectively). High Cdk5 expression was associated with shorter progression‐free survival (P = .006). These data suggest a role for DARPP‐32 and associated signalling kinases as prognostic markers with clinical utility in ovarian cancer.

ASCL1-regulated DARPP-32 and t-DARPP stimulate small cell lung cancer growth and neuroendocrine tumour cell proliferation

Background

Small cell lung cancer (SCLC) is the most aggressive form of lung cancer, and new molecular insights are necessary for prognostic and therapeutic advances.

Methods

Dopamine and cAMP-regulated phosphoprotein, Mr 32000 (DARPP-32) and its N-terminally truncated splice variant, t-DARPP, were stably overexpressed or ablated in human DMS-53 and H1048 SCLC cells. Functional assays and immunoblotting were used to assess how DARPP-32 isoforms regulate SCLC cell growth, proliferation, and apoptosis. DARPP-32-modulated SCLC cells were orthotopically injected into the lungs of SCID mice to evaluate how DARPP-32 and t-DARPP regulate neuroendocrine tumour growth. Immunostaining for DARPP-32 proteins was performed in SCLC patient-derived specimens. Bioinformatics analysis and subsequent transcription assays were used to determine the mechanistic basis of DARPP-32-regulated SCLC growth.

Results

We demonstrate in mice that DARPP-32 and t-DARPP promote SCLC growth through increased Akt/Erk-mediated proliferation and anti-apoptotic signalling. DARPP-32 isoforms are overexpressed in SCLC patient-derived tumour tissue, but undetectable in physiologically normal lung. Achaete-scute homologue 1 (ASCL1) transcriptionally activates DARPP-32 isoforms in human SCLC cells.

Conclusions

We reveal new regulatory mechanisms of SCLC oncogenesis that suggest DARPP-32 isoforms may represent a negative prognostic indicator for SCLC and serve as a potential target for the development of new therapies.

Dopamine and cAMP-regulated phosphoprotein 32 kDa (DARPP-32) and survival in breast cancer: a retrospective analysis of protein and mRNA expression

Dopamine and cAMP regulated phosphoprotein 32 kDa (DARPP-32) also known as phosphoprotein phosphatase-1 regulatory subunit 1B and encoded by the PPP1R1B gene is an inhibitor of protein phosphatase-1 and protein kinase A. DARPP-32 is expressed in a wide range of epithelial cells and some solid tumours; however, its role in breast cancer is only partially defined. DARPP-32 expression was determined using immunohistochemistry in two independent cohorts of early stage invasive breast cancer patients (discovery n = 1352; validation n = 1655), and 112 HER2 positive breast cancer patients treated with trastuzumab and adjuvant chemotherapy. PPP1R1B mRNA expression was assessed in the METABRIC cohort (n = 1980), using artificial neural network analysis to identify associated genes. In the discovery cohort, low nuclear expression of DARPP-32 was significantly associated with shorter survival (P = 0.041), which was independent of other prognostic variables (P = 0.019). In the validation cohort, low cytoplasmic and nuclear expression was significantly associated with shorter survival (both P = 0.002), with cytoplasmic expression independent of other prognostic variables (P = 0.023). Stronger associations with survival in oestrogen receptor (ER) positive disease were observed. In patients treated with trastuzumab, low nuclear expression was significantly associated with adverse progression-free survival (P = 0.031). In the METABRIC cohort, low PPP1R1B expression was associated with shortened survival of ER positive patients. Expression of CDC42 and GRB7, amongst others, were associated with PPP1R1B expression. This data suggests a role for DARPP-32 as a prognostic marker with clinical utility in breast cancer.

IKKα Promotes the Progression and Metastasis of Non-Small Cell Lung Cancer Independently of its Subcellular Localization

Lung cancer is the leading worldwide cause of cancer mortality, however, neither curative treatments nor substantial prolonged survival has been achieved, highlighting the need for investigating new proteins responsible for its development and progression. IKKα is an essential protein for cell survival and differentiation, which expression is enhanced in human non-small cell lung cancer (NSCLC) and correlates with poor patient survival, appearing as a relevant molecule in lung cancer progression. However, there are not conclusive results about its role in this type of cancer. We have recently found that IKKα performs different functions and activates different signaling pathways depending on its nuclear or cytoplasmic localization in tumor epidermal cells. In this work, we have studied the involvement of IKKα in lung cancer progression through the generation of lung cancer cell lines expressing exogenous IKKα either in the nucleus or in the cytoplasm. We demonstrate that IKKα signaling promotes increased cell malignancy of NSCLC cells as well as lung tumor progression and metastasis in either subcellular localization, through activation of common protumoral proteins, such as Erk, p38 and mTor. But, additionally, we found that depending on its subcellular localization, IKKα has non-overlapping roles in the activation of other different pathways known for their key implication in lung cancer progression: while cytoplasmic IKKα increases EGFR and NF-κB activities in lung tumor cells, nuclear IKKα causes lung tumor progression through c-Myc, Smad2/3 and Snail activation. These results suggest that IKKα may be a promising target for intervention in human NSCLC.

Darpp-32 and t-Darpp protein products of PPP1R1B: Old dogs with new tricks

The PPP1R1B gene is located on chromosome 17q12 (39,626,208-39,636,626[GRCh38/hg38]), which codes for multiple transcripts and two experimentally-documented proteins Darpp-32 and t-Darpp. Darpp-32 (Dopamine and cAMP Regulated Phosphoprotein), discovered in the early 1980s, is a protein whose phosphorylation is upregulated in response to cAMP in dopamine-responsive tissues in the brain. It's phosphorylation profile modulates its ability to bind and inhibit Protein Phosphatase 1 activity, which, in turn, controls the activity of hundreds of phosphorylated proteins. PPP1R1B knockout mice exhibit subtle learning defects. In 2002, the second protein product of PPP1R1B was discovered in gastric cancers: t-Darpp (truncated Darpp-32). The start codon of t-Darpp is amino acid residue 37 of Darpp-32 and it lacks the domain responsible for modulating Protein Phosphatase 1. Aside from gastric cancers, t-Darpp and/or Darpp-32 is overexpressed in tumor cells from breast, colon, esophagus, lung and prostate tissues. More than one research team has demonstrated that these proteins, through mechanisms that to date remain cloudy, activate AKT, a protein whose phosphorylation leads to cell survival and blocks apoptosis. Furthermore, in Her2 positive breast cancers (an aggressive form of breast cancer), t-Darpp/Darpp-32 overexpression causes resistance to the frequently-administered anti-Her2 drug, trastuzumab (Herceptin), likely through AKT activation. Here we briefly describe how Darpp-32 and t-Darpp were discovered and report on the current state of knowledge of their involvement in cancers. We present a case for the development of an anti-t-Darpp therapeutic agent and outline the unique challenges this endeavor will likely encounter.

Suppression of cyclooxygenase 2 increases chemosensitivity to sesamin through the Akt‑PI3K signaling pathway in lung cancer cells

Safe, affordable and efficacious agents are urgently required for cancer prevention. Sesamin, a lipid‑soluble lignan from sesame (Sesamum indicum) displays anticancer activities through an unknown mechanism. In the present study, the anticancer activity of sesamin via cyclooxygenase 2 (COX2) was investigated in lung cancer. Quantitative polymerase chain reaction was performed to determine the mRNA expression levels of COX2 in cells, while western blot analysis was used to determine its protein expression levels. Cell proliferation was evaluated by Cell Counting Kit‑8 assay, while apoptosis and cell cycle analyses were conducted by flow cytometry. The results indicated that COX2 expression was upregulated in lung cancer cell lines compared with human normal lung epithelial cell line BEAS‑2B and sesamin was demonstrated to decrease the levels of COX2, inhibit the proliferation of lung cancer cells and promote their apoptosis in a concentration‑dependent manner. Furthermore, decreased COX2 expression potentiated sesamin‑induced apoptosis and G1‑phase arrest, which was correlated with the suppression of gene products associated with cell apoptosis (Bcl‑2 and Bax) and the cell cycle (cyclin E1). In addition, cotreatment with the COX2 inhibitor CAY10404 and sesamin downregulated the expression of downstream molecules of COX2 [including interleukin (IL)1β, IL6 and tumor necrosis factor α] compared with CAY10404 or sesamin alone. Furthermore, cotreatment with sesamin and CAY10404 markedly reduced the levels of phosphorylated protein kinase B (pAkt) and phosoinositide 3 kinase (PI3K) in three lung cancer cell lines. PI3K expression was observed to be under the control of COX2, possibly forming a negative feedback loop. In addition, PI3K depletion induced apoptosis and G1‑phase arrest in A549 cells. These results suggested that sesamin blocked the pAkt‑PI3K signaling pathway by downregulating the expression of COX2, therefore resulting in cell cycle arrest and increased apoptosis in vitro. In conclusion, inhibition of COX2 increased the sensitivity of lung cancer cells to sesamin by modulating pAkt‑PI3K signaling. These results may aid the development of more selective agents to overcome cancer.