The PDZ-LIM domain-containing protein PDLIM2 is a common tumor suppressor and a key immune modulator. One main function of PDLIM2 is to promote the ubiquitination and proteasomal degradation of nuclear activated NF-κB RelA, a physiologically indispensable transcription factor whose persistent activation has been linked to almost all cancer types and inflammation-associated diseases. However, it remains unknown how PDLIM2 exerts this physiologically and pathogenically important function. Here, we show that PDLIM2 acts as a ubiquitin ligase enhancer, termed E5. It stabilizes ROC1, an essential component of SKP1/Cullin/F-box protein (SCF) ubiquitin ligases, and chaperones the ROC1-SCFβ-TrCP ubiquitin ligase to ubiquitinate nuclear RelA for proteasomal degradation in the nucleus. Consistently, silencing of ROC1, Cullin 1 or the F-box protein β-TrCP blocks RelA ubiquitination and degradation by PDLIM2. These data provide new mechanistic insights into how PDLIM2 promotes nuclear RelA ubiquitination and degradation, thereby serving as a critical tumor suppressor and a vital immune regulator. They also improve our understanding of the complex cascade of the ubiquitination and NF-κB pathways, particularly given the well-known role of the ROC1-SCFβ-TrCP ubiquitin ligase in initiating NF-κB activation by directly binding to and ubiquitinating NF-κB inhibitors for the proteasomal degradation in the cytoplasm.

BACKGROUND: Emerging evidence indicates the pivotal involvement of circular RNAs (circRNAs) in cancer initiation and progression. Understanding the functions and underlying mechanisms of circRNAs in tumor development holds promise for uncovering novel diagnostic indicators and therapeutic targets. In this study, our focus was to elucidate the function and regulatory mechanism of hsa-circ-0003764 in hepatocellular carcinoma (HCC).
METHODS: A newly discovered hsa-circ-0003764 (circPTPN12) was identified from the circbase database. QRT-PCR analysis was utilized to assess the expression levels of hsa-circ-0003764 in both HCC tissues and cells. We conducted in vitro and in vivo experiments to examine the impact of circPTPN12 on the proliferation and apoptosis of HCC cells. Additionally, RNA-sequencing, RNA immunoprecipitation, biotin-coupled probe pull-down assays, and FISH were employed to confirm and establish the relationship between hsa-circ-0003764, PDLIM2, OTUD6B, P65, and ESRP1.
RESULTS: In HCC, the downregulation of circPTPN12 was associated with an unfavorable prognosis. CircPTPN12 exhibited suppressive effects on the proliferation of HCC cells both in vitro and in vivo. Mechanistically, RNA sequencing assays unveiled the NF-κB signaling pathway as a targeted pathway of circPTPN12. Functionally, circPTPN12 was found to interact with the PDZ domain of PDLIM2, facilitating the ubiquitination of P65. Furthermore, circPTPN12 bolstered the assembly of the PDLIM2/OTUD6B complex by promoting the deubiquitination of PDLIM2. ESRP1 was identified to bind to pre-PTPN12, thereby fostering the generation of circPTPN12.
CONCLUSIONS: Collectively, our findings indicate the involvement of circPTPN12 in modulating PDLIM2 function, influencing HCC progression. The identified ESRP1/circPTPN12/PDLIM2/NF-κB axis shows promise as a novel therapeutic target in the context of HCC.

BACKGROUND: Cancer is characterized by dysregulated cellular metabolism. Thus, understanding the mechanisms underlying these metabolic alterations is important for developing targeted therapies. In this study, we investigated the pro-tumoral effect of PDZ and LIM domain 2 (PDLIM2) downregulation in lung cancer growth and its association with the accumulation of mitochondrial ROS, oncometabolites and the activation of hypoxia-inducible factor-1 (HIF-1) α in the process.
METHODS: Databases and human cancer tissue samples were analyzed to investigate the roles of PDLIM2 and HIF-1α in cancer growth. DNA microarray and gene ontology enrichment analyses were performed to determine the cellular functions of PDLIM2. Seahorse assay, flow cytometric analysis, and confocal microscopic analysis were employed to study mitochondrial functions. Oncometabolites were analyzed using liquid chromatography-mass spectrometry (LC-MS). A Lewis lung carcinoma (LLC) mouse model was established to assess the in vivo function of PDLIM2 and HIF-1α.
RESULTS: The expression of PDLIM2 was downregulated in lung cancer, and this downregulation correlated with poor prognosis in patients. PDLIM2 highly regulated genes associated with mitochondrial functions. Mechanistically, PDLIM2 downregulation resulted in NF-κB activation, impaired expression of tricarboxylic acid (TCA) cycle genes particularly the succinate dehydrogenase (SDH) genes, and mitochondrial dysfunction. This disturbance contributed to the accumulation of succinate and other oncometabolites, as well as the buildup of mitochondrial reactive oxygen species (mtROS), leading to the activation of hypoxia-inducible factor 1α (HIF-1α). Furthermore, the expression of HIF-1α was increased in all stages of lung cancer. The expression of PDLIM2 and HIF-1α was reversely correlated in lung cancer patients. In the animal study, the orally administered HIF-1α inhibitor, PX-478, significantly reduces PDLIM2 knockdown-promoted tumor growth.
CONCLUSIONS: These findings shed light on the complex action of PDLIM2 on mitochondria and HIF-1α activities in lung cancer, emphasizing the role of HIF-1α in the tumor-promoting effect of PDLIM2 downregulation. Additionally, they provide new insights into a strategy for precise targeted treatment by suggesting that HIF-1α inhibitors may serve as therapy for lung cancer patients with PDLIM2 downregulation.

PDZ-LIM domain-containing Protein 2 (PDLIM2) has been reported to be downregulated in ovarian cancer. However, its exact function and mechanism in regulating ovarian cancer progression have not been elucidated. This work researched the exert effect and mechanism of PDLIM2 on ovarian cancer progression. Briefly, PDLIM2 expression in clinical tissues of ovarian cancer patients and cells was investigated by qRT-PCR and Western blot. The function of PDLIM2 on the proliferation, colony formation, migration and invasion of ovarian cancer cells was explored via cell counting kit-8, colony formation and Transwell assays. To verify whether PDLIM2 regulates ovarian cancer progression via regulating the transforming growth factor-β (TGF-β)/Smad pathway, exogenous TGF-β (10 ng/mL) treatment was performed on the PDLIM2-overexpressed ovarian cancer cells. PDLIM2 effect on the in vivo growth of ovarian cancer cells was researched by establishing a xenograft tumor model. Immunohistochemistry and Western blot were performed to protein expression in cells and tissues. As a result, PDLIM2 was low-expressed in ovarian cancer tissues/cells. PDLIM2 upregulation attenuated the proliferation, colony formation, migration, invasion and epithelial-mesenchymal transition (EMT) of ovarian cancer cells, and inactivated the TGF-β/Smad pathway. The opposite results were found in the PDLIM2-silenced ovarian cancer cells. Exogenous TGF-β treatment abrogated the inhibition of PDLIM2 on the malignant behavior of ovarian cancer cells. PDLIM2 upregulation attenuated the in vivo growth and EMT of ovarian cancer cells. Thus, PDLIM2 attenuates the proliferation, migration, invasion and EMT of ovarian cancer cells via inactivating the TGF-β/Smad pathway. PDLIM2 may be a usefully target for ovarian cancer treatment.

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder that is associated with neurological symptoms, including autism spectrum disorder. Tuberous sclerosis complex is caused by pathogenic germline mutations of either the TSC1 or TSC2 gene, but somatic mutations were identified in both genes, and the combined effects of TSC1 and TSC2 mutations have been unknown.
The present study investigated social behaviors by the social interaction test and three-chambered sociability tests, effects of rapamycin treatment, and gene expression profiles with a gene expression microarray in Tsc1 and Tsc2 double heterozygous mutant (TscD+/-) mice.
TscD+/- mice exhibited impairments in social behaviors, and the severity of impairments was similar to Tsc2+/- mice rather than Tsc1+/- mice. Impairments in social behaviors were rescued by rapamycin treatment in all mutant mice. Gene expression profiles in the brain were greatly altered in TscD+/- mice more than in Tsc1+/- and Tsc2+/- mice. The gene expression changes compared with wild type (WT) mice were similar between TscD+/- and Tsc2+/- mice, and the overlapping genes whose expression was altered in mutant mice compared with WT mice were enriched in the neoplasm- and inflammation-related canonical pathways. The \"signal transducer and activator of transcription 3, interferon regulatory factor 1, interferon regulatory factor 4, interleukin-2R α chain, and interferon-γ\" signaling pathway, which is initiated from signal transducer and activator of transcription 4 and PDZ and LIM domain protein 2, was associated with impairments in social behaviors in all mutant mice.
It is unclear whether the signaling pathway also plays a critical role in autism spectrum disorders not caused by Tsc1 and Tsc2 mutations.
These findings suggest that TSC1 and TSC2 double mutations cause autistic behaviors similarly to TSC2 mutations, although significant changes in gene expression were attributable to the double mutations. These findings contribute to the knowledge of genotype-phenotype correlations in TSC and suggest that mutations in both the TSC1 and TSC2 genes act in concert to cause neurological symptoms, including autism spectrum disorder.

We have previously reported that β-aminoisobutyric acid (BAIBA), a muscle-derived exercise mimetic, had anti-inflammatory and reactive oxygen species (ROS) scavenging effects in vascular endothelial cells through the enhanced expression of peroxisome proliferator-activated receptor gamma coactivator-1β (PGC-1β). Although BAIBA also increased the expression of estrogen-related receptor α (ERRα), the roles of ERRα in vascular endothelial cells have yet to be fully elucidated. Here, we found that human aortic endothelial cells (HAECs) infected with ERRα-expressing adenovirus had significantly decreased mRNA levels of tumor necrosis factor α-stimulated proinflammatory molecules. However, ERRα overexpression had little effect on the mRNA levels of PGC-1β, peroxisome proliferator-activated receptors, and almost all ROS scavenging molecules, except for superoxide dismutase 2. ERRα expression significantly decreased NFκB reporter activities in a dose-dependent manner with unaltered IκBα phosphorylation levels but with a significant increase in the mRNA levels of PDZ and LIM domain protein 2 (PDLIM2) and copper metabolism gene MURR1 domain-containing protein (COMMD1), which enhance the ubiquitination and degradation of NFκB. Also, PDLIM2 and COMMD1 mRNA levels were upregulated in BAIBA-treated HAECs. Finally, we identified the ERRα-response element in the COMMD1 promoter region (-283 to -29 bp). These results indicated that ERRα exerted anti-inflammatory effects in vascular endothelial cells through COMMD1-mediated attenuation of NFκB activity, which could be an atheroprotective mechanism of physical exercise.

The PDZ-LIM domain-containing protein 2 (PDLIM2) regulates cell polarity and the protein stability of key transcription factors in epithelial and hemopoietic cells. We previously reported that PDLIM2 is more highly expressed in Triple Negative Breast Cancer (TNBC) than in other breast cancer types or normal breast tissue. In the course of the TNBC study, it was noted that PDLIM2 was highly expressed in the stroma of PDLIM2-expressing tumours. Here, we investigated the phenotype of these stromal cells and whether any infiltrating immune population was linked to PDLIM2 expression. We found that high PDLIM2 expression in breast tumours was associated with higher levels of infiltrating M2 macrophages, but was not associated with infiltrating T cell sub-populations. We then tested whether PDLIM2 contributes to macrophage differentiation or function by using cultures of bone marrow-derived macrophages from wildtype and Pdlim2 knockout mice. This demonstrated that PDLIM2 is required for naïve macrophage migration and for the full adoption of IL-4-induced M2 polarization, including expression of M2 phenotypic markers, cell adhesion and cell migration. TLR4-, TLR3- or IFNγ-induced M1 macrophage activity was less dependent on PDLIM2. Finally, analysis of publicly available breast cancer datasets showed that high PDLIM2 expression is associated with increased M2 macrophage infiltration. We conclude that PDLIM2 expression influences the tumour associated stroma and, in particular, M2 macrophage infiltration that may contribute to the progression of TNBC or other subsets of breast cancer.

Rheumatoid arthritis (RA) is an autoimmune disease caused by synovitis. Two genes, KLF10 (Kruppel like factor 10) and PDZ and LIM domain containing protein 2 (PDLIM2), play key roles in cell inflammation and proliferation. However, the specific roles of the two on inflammation and proliferation of RA-fibroblastoid synovial cell (RA-FLS) have not been reported so far. RT-qPCR and Western blot detected the expressions of PDLIM2 and KLF10 in Human Rheumatoid arthritis FLSs (HFLSs-RA). Cell transfection techniques overexpressed PDLIM2 and KLF10 or inhibited the expression of KLF10. JAPAR database predicted the binding sites of PDLIM2 and KLF10, and the binding between the two was detected and verified using luciferase reporter genes and ChIP. Subsequently, CCK-8 technology, TUNEL staining, Western blot, wound healing and ELISA detected proliferation-related indicators, migration-related indications and inflammation-related indicators. Finally, western blot was used to detect the expression of NF-κB pathway related proteins to further explore the mechanism.The expression of PDLIM2 was decreased in HFLSs-RA. Overexpression of PDLIM2 inhibited proliferation, migration and inflammation in HFLSs-RA. KLF10 can transcriptionally activate PDLIM2. Interfering with KLF10 reversed the inhibition effects of PDLIM2 overexpression on the proliferation, migration and inflammation, which was possibly through the NF-κB pathway. Overall, KLF10 can up-regulate PDLIM2 by regulating the NF-κB pathway to inhibit inflammation and proliferation of HFLSs-RA.

PDZ and LIM domains-containing proteins play pivotal functions in cell cytoskeleton organization, cell polarization and differentiation. As a key member of the family, PDLIM2 regulates stability and activity of transcription factors such as NF-κB, STATs and β-catenin, and thus exert it functions in inflammation, immunity, and cancer. PDLIM2 functions as a tumor suppressor in multiple tissues and it is often genetically mutated or epigenetically silenced in human cancers derived from lung, breast, ovarian and other histologies. However, in certain types of cancers, PDLIM2 may promote cancer cell proliferation and metastases. Therefore, PDLIM2 is added to a long list of genes that can function as tumor suppressor or oncogenic protein. During tumorigenesis induced by oncogenic viruses, PDLIM2 is a key target. Through promotion of NF-κB/RelA and STAT3 degradation, PDLIM2 enhances expression of proteins involved in antigen presentation and promotes T-cell activation while repressing multidrug resistance genes, thereby rendering mutated cells susceptible to immune surveillance and cytotoxicity mediated by immune cells and chemotherapeutic drugs. Intriguingly, PDLIM2 in alveolar macrophages (AMs) plays key roles in monitoring lung tumorigenesis, as its selective genetic deletion leads to constitutive activation of STAT3, driving monocyte differentiation to AMs with pro-tumorigenic polarization and activation. PDLIM2 has also been explored as a therapeutic target for cancer therapy. At the end of this review, we provide perspectives on this important molecule and discuss the future directions of both basic and translational studies.

We evaluated the expression of PDLIM2 in human kidney cancer cell lines from primary or metastatic origins and found that PDLIM2 expression was highly elevated in metastatic kidney cancers. We evaluated the effect of PDLIM2 inhibition by RNA interference method. PDLIM2 knockdown showed the decreased proliferation and metastatic character in human metastatic kidney cancer cells. By repeated round of orthotopic injection of RenCa mouse kidney cancer cell line, we obtained metastatic prone mouse kidney cancer cell lines. PDLIM2 expression was highly expressed in these metastatic prone cells comparing parental cells. In addition, we evaluated the in vivo efficacy of PDLIM2 knockout on the tumor formation and metastasis of kidney cancer cells using a PDLIM2 knockout mice. The experimental metastasis model with tail vein injection and orthotopic metastasis model injected into kidney all showed reduced lung metastasis cancer formation in PDLIM2 knockout mice comparing control Balb/c mice. Overall, our findings indicate that PDLIM2 is required for cancer formation and metastasis in metastatic kidney cancer, indicating that PDLIM2 may be a new therapeutic target for metastatic kidney cancer.