Over-expression of prothymosin-α antagonizes TGFβ signalling to promote the development of emphysema

Pan-cancer secreted proteome and skeletal muscle regulation: insight from a proteogenomic data-driven knowledge base

Large-scale, pan-cancer analysis is enabled by data driven knowledge bases that link tumor molecular profiles with phenotypes. A debilitating cancer-related phenotype is skeletal muscle loss, or cachexia, which occurs partly from tumor products secreted into circulation. Using the LinkedOmicsKB knowledge base assembled from the Clinical Proteomics Tumor Analysis Consortium proteogenomic analysis, along with catalogs of human secretome proteins, ligand-receptor pairs and molecular signatures, we sought to identify candidate pan-cancer proteins secreted to blood that could regulate skeletal muscle phenotypes in multiple solid cancers. Tumor proteins having significant pan-cancer associations with muscle were referenced against secretome proteins secreted to blood from the Human Protein Atlas, then verified as increased in paired tumor vs. normal tissues in pan-cancer manner. This workflow revealed seven secreted proteins from cancers afflicting kidneys, head and neck, lungs and pancreas that classified as protein-binding activity modulator, extracellular matrix protein or intercellular signaling molecule. Concordance of these biomarkers with validated molecular signatures of cachexia and senescence supported relevance to muscle and cachexia disease biology, and high tumor expression of the biomarker set associated with lower overall survival. In this article, we discuss avenues by which skeletal muscle and cachexia may be regulated by these candidate pan-cancer proteins secreted to blood, and conceptualize a strategy that considers them collectively as a biomarker signature with potential for refinement by data analytics and radiogenomics for predictive testing of future risk in a non-invasive, blood-based panel amenable to broad uptake and early management.

The TIMP protein family: diverse roles in pathophysiology

The tissue inhibitors of matrix metalloproteinases (TIMPs) are a family of four matrisome proteins classically defined by their roles as the primary endogenous inhibitors of metalloproteinases (MPs). Their functions however are not limited to MP inhibition, with each family member harboring numerous MP-independent biological functions that play key roles in processes such as inflammation and apoptosis. Because of these multifaceted functions, TIMPs have been cited in diverse pathophysiological contexts. Herein, we provide a comprehensive overview of the MP-dependent and -independent roles of TIMPs across a range of pathological conditions. The potential therapeutic and biomarker applications of TIMPs in these disease contexts are also considered, highlighting the biomedical promise of this complex and often misunderstood protein family.

Transcriptome analysis of multiple tissues reveals the potential mechanism of death under acute heat stress in chicken

BACKGROUND

Acute heat stress could induce high mortality and cause huge economic losses in the poultry industry. Although many studies have revealed heat stress-induced injuries of multiple tissues, the main target tissue and molecular mechanism of death under acute heat stress was largely unknown. This study systematically compared the transcriptome data of five main visceral tissues in chickens to reveal the response of multiple tissues to acute heat stress and determine the main target tissue of acute heat stress, further revealing the injuries of main target tissue and their potential mechanism by combing pathological section and qRT-PCR technologies.

RESULTS

The transcriptome data of five visceral tissues revealed that acute heat stress broadly caused inflammatory response and damaged tissues metabolic homeostasis. Among the five tested visceral tissues, the number of differentially expressed genes in the lung was the highest, and their fold changes were the greatest, indicating that the lung was the main target tissue of acute heat stress. The results of pathological section revealed severe inflammation, emphysema and pulmonary hemorrhage in the lung under acute heat stress. Our study found that some pro-inflammatory genes, including CNTFR, FURIN, CCR6, LIFR and IL20RA, were significantly up-regulated both in the heat-stress and heat-death groups, and their fold changes in the heat-death group were significantly greater than that in the heat-stress group. We also found an anti-inflammatory gene, AvBD9, exhibiting an extremely high expression in the heat-stress group but a low expression in the heat-death group.

CONCLUSIONS

Our study found that acute heat stress caused multiple tissue injuries broadly and the lung was the main target tissue of acute heat stress in chicken. Acute heat stress caused a severe inflammatory response, emphysema, and pulmonary haemorrhage, The severe inflammatory response in the heat-death group was related to the up-regulation of pro-inflammatory genes and down-regulation of anti-inflammatory genes.

Prothymosin α-derived hexapeptide prevents the brain damage and sequelae due to ischemia-hemorrhage

ProTα discovered as a necrosis-inhibitor from the conditioned medium of cortical culture also shows a potent survival action in brain and retinal ischemia/reperfusion models. The proposed mechanisms are the initial cell death mode switch from necrosis to apoptosis, which is subsequently inhibited by neurotrophic factors in vivo. It should be noted that ProTα and its derived hexapeptide P6Q completely suppress the cerebral hemorrhage induced by late tPA treatment (4.5 h) after the brain ischemia/reperfusion. Mechanisms underlying their beneficial actions may be related to the fact that ProTα inhibits the production of matrix metalloproteases (MMPs) in microglia and vascular endothelial cells. However, as P6Q inhibits MMPs in vascular endothelial cells, but not in microglia, the suppression of MMP production in endothelial cells seems to play major roles in the late tPA-induced hemorrhage. Although the tPA-treatments could enable the survival of patients with stroke, the post-stroke sequelae are the next clinical issues to be solved. The use of small peptide P6Q revealed the blockade of post-stroke pain, depression and memory-learning deficits in animal models. Furthermore, recent studies also showed that P6Q supplementation increased the viability of human induced pluripotent stem (iPS) cell-derived retinal pigment epithelium cell suspensions during the storage and P6Q attenuated the cisplatin-induced acute kidney injury.

AhR Activation Leads to Attenuation of Murine Autoimmune Hepatitis: Single-Cell RNA-Seq Analysis Reveals Unique Immune Cell Phenotypes and Gene Expression Changes in the Liver

The aryl hydrocarbon receptor (AhR) is a ubiquitously expressed ligand-activated transcription factor. While initially identified as an environmental sensor, this receptor has been shown more recently to regulate a variety of immune functions. AhR ligands vary in structure and source from environmental chemicals such as 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and indoles found in cruciferous vegetables to endogenous ligands derived from tryptophan metabolism. In the current study, we used TCDD, a high affinity AhR ligand to study the impact of AhR activation in the murine model of autoimmune hepatitis (AIH). Primarily, we used single-cell RNA-sequencing (scRNA-seq) technology to study the nature of changes occurring in the immune cells in the liver at the cellular and molecular level. We found that AhR activation attenuated concanavalin A (ConA)-induced AIH by limiting chemotaxis of pro-inflammatory immune cell subsets, promoting anti-inflammatory cytokine production, and suppressing pro-inflammatory cytokine production. scRNA-seq analysis showed some unusual events upon ConA injection such as increased presence of mature B cells, natural killer (NK) T cells, CD4+ or CD8+ T cells, Kupffer cells, memory CD8+ T cells, and activated T cells while TCDD treatment led to the reversal of most of these events. Additionally, the immune cells showed significant alterations in the gene expression profiles. Specifically, we observed downregulation of inflammation-associated genes including Ptma, Hspe1, and CD52 in TCDD-treated AIH mice as well as alterations in the expression of migratory markers such as CXCR2. Together, the current study characterizes the nature of inflammatory changes occurring in the liver during AIH, and sheds light on how AhR activation during AIH attenuates liver inflammation by inducing phenotypic and genotypic changes in immune cells found in the liver.

Expression and function of Smad7 in autoimmune and inflammatory diseases

Transforming growth factor-β (TGF-β) plays a critical role in the pathological processes of various diseases. However, the signaling mechanism of TGF-β in the pathological response remains largely unclear. In this review, we discuss advances in research of Smad7, a member of the I-Smads family and a negative regulator of TGF-β signaling, and mainly review the expression and its function in diseases. Smad7 inhibits the activation of the NF-κB and TGF-β signaling pathways and plays a pivotal role in the prevention and treatment of various diseases. Specifically, Smad7 can not only attenuate growth inhibition, fibrosis, apoptosis, inflammation, and inflammatory T cell differentiation, but also promotes epithelial cells migration or disease development. In this review, we aim to summarize the various biological functions of Smad7 in autoimmune diseases, inflammatory diseases, cancers, and kidney diseases, focusing on the molecular mechanisms of the transcriptional and posttranscriptional regulation of Smad7.

Identification of hub genes and key pathways in the emphysema phenotype of COPD

Chronic obstructive pulmonary disease (COPD) is a heterogeneous condition associated with high morbidity and mortality. This study aimed to use weighted gene co-expression network analysis (WGCNA) to explore the molecular pathogenesis of the emphysema phenotype of COPD. After obtaining lung mRNA expression profiles from ten patients with the emphysema phenotype of COPD and eight controls, emphysema-associated gene modules were identified with WGCNA. Among 13 distinct modules, the green-yellow and brown modules showed the strongest correlations with emphysema severity and lung function and were thus selected as hub modules. On gene ontology analysis, these two modules were mainly enriched in immune response, B cell receptor (BCR) signaling pathway, extracellular matrix (ECM) organization, and collagen fibril organization. Pathway analysis primarily showed enrichment in BCR signaling pathways, ECM receptor interaction, and NF-κB and TGF-β signaling pathways for the two hub modules. Several genes, including FCRLA, MS4A1, CD19, FKBP10, C1S and HTRA1, among others, were identified as hub genes. Our results shed light on the potential genetic mechanisms underlying the pathogenesis of the emphysema phenotype of COPD. However, further research will be needed to confirm the involvement of the identified genes and to determine their therapeutic relevance.

ProT-α gene transfer attenuates cardiopulmonary remedying and mortality in a flow-induced pulmonary hypertension rat model

BACKGROUND

ProT is a cell survival gene, which modulates oxidative stress and transforming growth factor (TGF)-β signaling. We hypothesized that the delivery of the ProT cDNA gene in rats could protect against right heart dysfunction secondary to pulmonary hypertension (PH) induced by left-to-right shunt.

METHODS

A 2-hit rat model of flow-induced PH was used, and a single intravenous injection of adenoviral vectors (2 billion plaque-forming unit) carrying ProT or Luc gene was administered. The animals were euthanized 21 days after gene delivery to assess cardiopulmonary function, serum biochemistry, pulmonary artery (PA), and vasomotor reactivity. Immunohistology and immunoblotting of PA tissues were also performed.

RESULTS

ProT transduction significantly reduced PA pressure, right ventricle muscle mass, and wall stress, thereby improving the overall survival of the treated rat. Increased production of ProT through gene therapy preserved both the smooth muscle myosin heavy chain-II and α-smooth muscle actin while counteracting the abundance of TGF-β in PA. Protein abundances of phosphorylated p47-phox, heme oxygenase-1, caspase-3, inducible nitric oxide synthase, cyclo-oxygenase 2, and monocyte chemoattractant protein-1 in PA tissues were reduced. ProT also preserved microRNA-223, thereby suppressing the abundance of PARP-1, which is independent of hypoxia-inducible factor-1α signaling.

CONCLUSIONS

ProT gene transduction improved PA function by reducing oxidative stress, attenuating inflammation, and preserving the contractile phenotype of vascular smooth muscle cells. The modification of microRNA-223-associated downstream signaling through ProT transduction may play an important role in mitigating cardiopulmonary remodeling in flow-induced PH.

Lysyl hydroxylase 3 increases collagen deposition and promotes pulmonary fibrosis by activating TGFβ1/Smad3 and Wnt/β-catenin pathways

INTRODUCTION

Lysyl hydroxylase 3 (LH3) is a collagen post-translational modifying enzyme; it is abnormally activated during the formation of collagen cross-links. iCRT3 is an inhibitor of both Wnt and β-catenin responsive transcription. We hypothesized that LH3 is regulated by TGFβ1/Smad3 signaling and Wnt/β-catenin signaling pathways. Some evidence suggested that there is complicated cross-talk between the two signal pathways in the genesis of pulmonary fibrosis.

MATERIAL AND METHODS

The normal culturing human lung cancer cell line A549 was derived from pulmonary epithelial cells. Transforming growth factor-β1 (TGF-β1) was induced A549 cells of pulmonary fibrosis. MTT assays detected cell growth stimulation by TGF-β1; collagen pyridine-crosslinking contents were detected by ELISA kits. Immunofluorescence were used to evaluate expression of key molecules in PLOD3 (LH3), Wnt/β-catenin and TGFβ1/Smad3 pathways.

RESULTS

Our findings suggested that iCRT3 could decrease LH3 protein expression (p < 0.01), Wnt1, β-catenin and p-Smad3 protein expression (p < 0.05). Knock-down PLOD3 could decrease LH3, collagen I gene and protein expression (p < 0.05). These effects were associated with decreasing collagen pyridine-crosslinking production (p < 0.05). However, ovexpression PLOD3 could increase LH3, collagen I gene and protein expression (p < 0.05). The result showed that LH3 plays an important role in collagen post-translational modifications, and it is regulated by Wnt/β-catenin and TGFβ1/Smad3 pathways.

CONCLUSIONS

This study suggests that PLOD3 (LH3) represents a target to prevent pulmonary fibrosis.

Prothymosin α promotes STAT3 acetylation to induce cystogenesis in Pkd1-deficient mice

Polycystic kidney disease (PKD) is characterized by the expansion of fluid-filled cysts in the kidney, which impair the function of kidney and eventually leads to end-stage renal failure. It has been previously demonstrated that transgenic overexpression of prothymosin α (ProT) induces the development of PKD; however, the underlying mechanisms remain unclear. In this study, we used a mouse PKD model that sustains kidney-specific low-expression of Pkd1 to illustrate that aberrant up-regulation of ProT occurs in cyst-lining epithelial cells, and we further developed an in vitro cystogenesis model to demonstrate that the suppression of ProT is sufficient to reduce cyst formation. Next, we found that the expression of ProT was accompanied with prominent augmentation of protein acetylation in PKD, which results in the activation of downstream signal transducer and activator of transcription (STAT) 3. The pathologic role of STAT3 in PKD has been previously reported. We determined that this molecular mechanism of protein acetylation is involved with the interaction between ProT and STAT3; consequently, it causes the deprivation of histone deacetylase 3 from the indicated protein. Conclusively, these results elucidate the significant role of ProT, including protein acetylation and STAT3 activation in PKD, which represent potential for ameliorating the disease progression of PKD.-Chen, Y.-C., Su, Y.-C., Shieh, G.-S., Su, B.-H., Su, W.-C., Huang, P.-H., Jiang, S.-T., Shiau, A.-L., Wu, C.-L. Prothymosin α promotes STAT3 acetylation to induce cystogenesis in Pkd1-deficient mice.

Expression of prothymosin α in lung cancer is associated with squamous cell carcinoma and smoking

Prothymosin α (ProTα) is a nuclear protein that serves a role in oncogenesis, by promoting proliferation and inhibiting apoptosis in various malignancies. The present study was designed to investigate ProTα expression in resected human non-small cell lung cancer to define the clinicopathological associations of ProTα-positive lung cancer. Immunohistochemical staining of ProTα was performed using tumor sample slides from 149 patients with non-small cell lung cancer, who underwent surgical resection. Association between the expression of ProTα and the following clinicopathological parameters was accessed: Age, sex, stage, lymph node involvement, pathological subtype, recurrence and cigarette smoking. A total of 85 tumors (57%) were classified as ProTα-positive lung cancer by staining intensity and 73 tumors (49%) were regarded as ProTα-positive by scoring index. The majority of patients with ProTα-positive tumors were younger (P=0.05) and had squamous cell carcinoma (P<0.01) compared with older and adenocarcinoma. Positive expression of ProTα by staining intensity was associated with a higher incidence rate of cancer recurrence (P=0.05) compared with negative ProTα expression. ProTα was also associated with cigarette smoking, particularly in the group with squamous cell carcinoma. Therefore, the present data suggested that ProTα-positive non-small cell lung cancer was associated with younger patients, squamous cell carcinoma, cigarette smoking and a higher incidence recurrence rate, subsequently indicating a subtype consisting of patients with smoking-associated inferior outcomes.

Prothymosin-α enhances phosphatase and tensin homolog expression and binds with tripartite motif-containing protein 21 to regulate Kelch-like ECH-associated protein 1/nuclear factor erythroid 2-related factor 2 signaling in human bladder cancer

Prothymosin‐α (PTMA) is a small, acidic protein that is usually transported into the nucleus and involves many cellular and immunological functions. Previous studies demonstrated that aberrant location of PTMA expression exists in human bladder cancer, but the role of PTMA protein expression remains elusive. In this study, we created ectopic nuclear or cytoplasmic PTMA expression in human bladder cancer cells by infecting lentiviruses carrying wild type or deleted nuclear localization signal of the PTMA gene. The in vivo tumorigenesis assay showed PTMA protein with deleted nuclear localization signal promotes J82 xenograft tumor growth in mice and shortens their survival more so than the wild type. Chromatin immunoprecipitation showed that wild‐type PTMA protein binds to the PTEN promoter and enhances phosphatase and tensin homolog (PTEN) expression. Through immunoblot proteomics and in vivo ubiquitination studies, PTMA protein can bind with tripartite motif‐containing protein 21 (TRIM21) and block its ubiquitination. Also, TRIM21 can downregulate both forms of PTMA protein. In human bladder tumors, loss of nuclear PTMA expression was an unfavorable prognostic indicator for shorter disease‐free survival (hazard ratio, 1.54; P = 0.009). Our data support that nuclear PTMA protein serves as a tumor suppressor in bladder cancer through upregulating PTEN and orchestrating TRIM21 for the regulation of Nrf2 signaling.

Asiatic acid prevents the development of interstitial lung disease in a hypochlorous acid-induced mouse model of scleroderma

Interstitial lung disease is the most common complication of systemic sclerosis (SSc) and is associated with a high rate of mortality. Due to the complex pathogenesis of SSc, the therapies currently available remain limited. In the present study, the effect of asiatic acid (AA) on SSc-associated pulmonary fibrosis (PF) and its association with the transforming growth factor-β1 (TGF-β1)/Smad2/3 signaling pathway were evaluated. A hypochlorous acid (HOCl)-induced model of SSc was used to evaluate the therapeutic effect of AA on PF in SSc, where AA was administered to SSc mice by gavage. PF was alleviated in the AA-treated SSc mice groups when examined under light microscopy. In addition, there was a decrease in histopathological progression and collagen in the lungs. AA significantly reduced expression of type I collagen in the lungs of mice with SSc. It also significantly suppressed α-smooth muscle actin expression, which attenuated the conversion of fibroblasts into muscle fibroblasts. These AA-associated antifibrosis and anti-immune effects were mediated through the significant downregulation of advanced oxidation protein product, E-selectin, and anti-DNA topoisomerase-1 autoantibody levels in the serum. Furthermore, the expression levels of TGF-β1 and the phosphorylated-Smad2/3/Smad2/3 ratios in AA-treated SSc mice were similar to the control. The presence of pulmonary inflammation and fibrosis was confirmed in the HOCl-induced SSc mice and the results demonstrated that selective inhibition of reactive oxygen species prevented PF. By focusing on the classical TGF-β1/Smad2/3 signaling pathway, a mechanism of action of AA was identified to be associated with the inhibition of Smad2/3 activation through negative regulation of Smad2/3 phosphorylation.

Macrophage-Restricted Shp2 Tyrosine Phosphatase Acts as a Rheostat for MMP12 through TGF-β Activation in the Prevention of Age-Related Emphysema in Mice

Persistent activation of macrophages in lungs plays a critical role in the production of matrix metalloproteinases (MMPs) that contributes to the destruction of alveolar walls, a hallmark for pulmonary emphysema. Dysregulated TGF-β1 signaling has been an essential determinant in the elevation of MMPs during the development of emphysema. Nevertheless, the mechanism for this MMP-dependent pathogenesis has yet to be clearly investigated. Recently, we identified an important role for tyrosine phosphatase Src homology domain-containing protein tyrosine phosphatase 2 (Shp2) in regulating the activation of alveolar macrophages. Over a long-term observation period, mice with Shp2 deletion in macrophages (LysMCre:Shp2^fl/fl ) develop spontaneous, progressive emphysema-like injury in the lungs, characterized by massive destruction of alveolar morphology, interstitial extracellular matrix degradation, and elevated levels of MMPs, particularly, significant increases of macrophage elastase (MMP12) in aged mice. Further analysis demonstrated that MMP12 suppression by TGF-β1 activation was apparently abrogated in LysMCre:Shp2^fl/fl mice, whereas the TGF-β1 concentration in the lungs was relatively the same. Mechanistically, we found that loss of Shp2 resulted in attenuated SMAD2/3 phosphorylation and nuclear translocation in response to TGF-β activation, thereby upregulating MMP12 expression in macrophages. Together, our findings define a novel physiological function of Shp2 in TGF-β1/MMP12-dependent emphysema, adding insights into potential etiologies for this chronic lung disorder.

Activation of Wnt/β-catenin signalling is required for TGF-β/Smad2/3 signalling during myofibroblast proliferation

Fibrosis in animal models and human diseases is associated with aberrant activation of the Wnt/β-catenin pathway. Despite extensive research efforts, effective therapies are still not available. Myofibroblasts are major effectors, responsible for extracellular matrix deposition. Inhibiting the proliferation of the myofibroblast is crucial for treatment of fibrosis. Proliferation of myofibroblasts can have many triggering effects that result in fibrosis. In recent years, the Wnt pathway has been studied as an underlying factor as a primary contributor to fibrotic diseases. These efforts notwithstanding, the specific mechanisms by which Wnt-mediated promotes fibrosis reaction remain obscure. The central role of the transforming growth factor-β (TGF-β) and myofibroblast activity in the pathogenesis of fibrosis has become generally accepted. The details of interaction between these two processes are not obvious. The present investigation was conducted to evaluate the level of sustained expression of fibrosis iconic proteins (vimentin, α-SMA and collagen I) and the TGF-β signalling pathway that include smad2/3 and its phosphorylated form p-smad2/3. Detailed analysis of the possible molecular mechanisms mediated by β-catenin revealed epithelial-mesenchymal transition and additionally demonstrated transitions of fibroblasts to myofibroblast cell forms, along with increased activity of β-catenin in regulation of the signalling network, which acts to counteract autocrine TGF-β/smad2/3 signalling. A major outcome of this study is improved insight into the mechanisms by which epithelial and mesenchymal cells activated by TGFβ1-smad2/3 signalling through Wnt/β-catenin contribute to lung fibrosis.

Nobiletin inhibits epithelial-mesenchymal transition of human non-small cell lung cancer cells by antagonizing the TGF-β1/Smad3 signaling pathway

Epithelial-mesenchymal transition (EMT) is a critical cellular process in cancer metastasis, during which epithelial polarized cells become motile mesenchymal cells. Since transforming growth factor-β (TGF-β) is a potent inducer of EMT, blocking of TGF-β/Smad signaling has become a promising cancer therapy. Nobiletin, a polymethoxy flavonoid from Citrus depressa, has been shown to be valuable for cancer treatment, yet the mechanism remains unclear. In the present study, lung adenocarcinoma A549 and H1299 cells were used to evaluate the effect of nobiletin on EMT induced by TGF-β1. Nobiletin successfully inhibited TGF-β1-induced EMT, migration, invasion and adhesion in vitro, accompanied by attenuation of MMP-2, MMP-9, p-Src, p-FAK, p-paxillin, Snail, Slug, Twist and ZEB1 expression. Nobiletin inhibited the transcriptional activity of Smads without changing the phosphorylation status or translocation of Smads induced by TGF-β1. Moreover, Smad3 is requisite in TGF-β1-stimulated EMT. Smad3 overexpression meaningfully impaired the ability of nobiletin to reverse TGF-β1-induced EMT. In vivo, nobiletin prohibited the growth of metastatic nodules in the lungs of nude mice. Moreover, nobiletin inhibited tumor growth and reversed EMT in mice bearing A549-Luc xenografts, as revealed by IVIS imaging and immunohistochemical analysis. Collectively, the data suggest that nobiletin prevents EMT by inactivating TGF-β1/Smad3 signaling.

Prothymosin Alpha and Immune Responses: Are We Close to Potential Clinical Applications?

The thymus gland produces soluble molecules, which mediate significant immune functions. The first biologically active thymic extract was thymosin fraction V, the fractionation of which led to the isolation of a series of immunoactive polypeptides, including prothymosin alpha (proTα). ProTα displays a dual role, intracellularly as a survival and proliferation mediator and extracellularly as a biological response modifier. Accordingly, inside the cell, proTα is implicated in crucial intracellular circuits and may serve as a surrogate tumor biomarker, but when found outside the cell, it could be used as a therapeutic agent for treating immune system deficiencies. In fact, proTα possesses pleiotropic adjuvant activity and a series of immunomodulatory effects (eg, anticancer, antiviral, neuroprotective, cardioprotective). Moreover, several reports suggest that the variable activity of proTα might be exerted through different parts of the molecule. We first reported that the main immunoactive region of proTα is the carboxy-terminal decapeptide proTα(100-109). In conjunction with data from others, we also revealed that proTα and proTα(100-109) signal through Toll-like receptor 4. Although their precise molecular mechanism of action is yet not fully elucidated, proTα and proTα(100-109) are viewed as candidate adjuvants for cancer immunotherapy. Here, we present a historical overview on the discovery and isolation of thymosins with emphasis on proTα and data on some immune-related new activities of the polypeptide and smaller immunostimulatory peptides thereof. Finally, we propose a compiled scenario on proTα's mode of action, which could eventually contribute to its clinical application.