The multi-functional cytokine transforming growth factor-β1 (TGF-β1) has growth inhibitory and anti-inflammatory roles during homeostasis and the early stages of cancer. Aberrant TGF-β activation in the late-stages of tumorigenesis, however, promotes development of aggressive growth characteristics and metastatic spread. Given the critical importance of this growth factor in fibrotic and neoplastic disorders, the TGF-β1 network is subject to extensive, multi-level negative controls that impact receptor function, mothers against decapentaplegic homolog 2/3 (SMAD2/3) activation, intracellular signal bifurcation into canonical and non-canonical pathways and target gene promotor engagement. Such negative regulators include phosphatase and tensin homologue (PTEN), protein phosphatase magnesium 1A (PPM1A), Klotho, bone morphogenic protein 7 (BMP7), SMAD7, Sloan-Kettering Institute proto-oncogene/ Ski related novel gene (Ski/SnoN), and bone morphogenetic protein and activin membrane-bound Inhibitor (BAMBI). The progression of certain cancers is accompanied by loss of expression, overexpression, mislocalization, mutation or deletion of several endogenous repressors of the TGF-β1 cascade, further modulating signal duration/intensity and phenotypic reprogramming. This review addresses how their aberrant regulation contributes to cellular plasticity, tumor progression/metastasis and reversal of cell cycle arrest and discusses the unexplored therapeutic value of restoring the expression and/or function of these factors as a novel approach to cancer treatment.

Elevated expression of the multifunctional cytokine transforming growth factor β1 (TGF-β1) is causatively linked to kidney fibrosis progression initiated by diabetic, hypertensive, obstructive, ischemic and toxin-induced injury. Therapeutically relevant approaches to directly target the TGF-β1 pathway (e.g., neutralizing antibodies against TGF-β1), however, remain elusive in humans. TGF-β1 signaling is subjected to extensive negative control at the level of TGF-β1 receptor, SMAD2/3 activation, complex assembly and promoter engagement due to its critical role in tissue homeostasis and numerous pathologies. Progressive kidney injury is accompanied by the deregulation (loss or gain of expression) of several negative regulators of the TGF-β1 signaling cascade by mechanisms involving protein and mRNA stability or epigenetic silencing, further amplifying TGF-β1/SMAD3 signaling and fibrosis. Expression of bone morphogenetic proteins 6 and 7 (BMP6/7), SMAD7, Sloan–Kettering Institute proto-oncogene (Ski) and Ski-related novel gene (SnoN), phosphate tensin homolog on chromosome 10 (PTEN), protein phosphatase magnesium/manganese dependent 1A (PPM1A) and Klotho are dramatically decreased in various nephropathies in animals and humans albeit with different kinetics while the expression of Smurf1/2 E3 ligases are increased. Such deregulations frequently initiate maladaptive renal repair including renal epithelial cell dedifferentiation and growth arrest, fibrotic factor (connective tissue growth factor (CTGF/CCN2), plasminogen activator inhibitor type-1 (PAI-1), TGF-β1) synthesis/secretion, fibroproliferative responses and inflammation. This review addresses how loss of these negative regulators of TGF-β1 pathway exacerbates renal lesion formation and discusses the therapeutic value in restoring the expression of these molecules in ameliorating fibrosis, thus, presenting novel approaches to suppress TGF-β1 hyperactivation during chronic kidney disease (CKD) progression.

Chronic kidney disease affects >15% of the U.S. population and >850 million individuals worldwide. Fibrosis is the common outcome of many chronic renal disorders and, although the etiology varies (i.e., diabetes, hypertension, ischemia, acute injury, and urologic obstructive disorders), persistently elevated renal TGF‐β1 levels result in the relentless progression of fibrotic disease. TGF‐β1 orchestrates the multifaceted program of renal fibrogenesis involving proximal tubular dysfunction, failed epithelial recovery and redifferentiation, and subsequent tubulointerstitial fibrosis, eventually leading to chronic renal disease. Recent findings implicate p53 as a cofactor in the TGF‐β1‐induced signaling pathway and a transcriptional coregulator of several TGF‐β1 profibrotic response genes by complexing with receptor‐activated SMADs, which are homologous to the small worms (SMA) and Drosophilia mothers against decapentaplegic (MAD) gene families. The cooperative p53‐TGF‐β1 genomic cluster includes genes involved in cell growth control and extracellular matrix remodeling [e.g., plasminogen activator inhibitor‐1 (PAI‐1; serine protease inhibitor, clade E, member 1), connective tissue growth factor, and collagen I]. Although the molecular basis for this codependency is unclear, many TGF‐β1‐responsive genes possess p53 binding motifs. p53 up‐regulation and increased p53 phosphorylation; moreover, they are evident in nephrotoxin‐ and ischemia/reperfusion‐induced injury, diabetic nephropathy, ureteral obstructive disease, and kidney allograft rejection. Pharmacologic and genetic approaches that target p53 attenuate expression of the involved genes and mitigate the fibrotic response, confirming a key role for p53 in renal disorders. This review focuses on mechanisms whereby p53 functions as a transcriptional regulator within the TGF‐β1 cluster with an emphasis on the potent fibrosis‐promoting PAI‐1 gene.—Higgins, C. E., Tang, J., Mian, B. M., Higgins, S. P., Gifford, C. C., Conti, D. J., Meldrum, K. K., Samarakoon, R., Higgins, P. J. TGF‐β1‐p53 cooperativity regulates a profibrotic genomic program in the kidney: molecular mechanisms and clinical implications. FASEB J. 33, 10596–10606 (2019). http://www.fasebj.org

Collagen type XI alpha 1 (COL11A1) is a novel biomarker associated with cisplatin resistance in ovarian cancer. We have previously reported that COL11A1 activates Src-Akt signaling through the collagen receptors discoidin domain receptor 2 (DDR2) and integrin α1β1 to confer cisplatin resistance to ovarian cancer cells. To identify the potential signaling molecules downstream of COL11A1 signaling, we performed protein kinase arrays and identified heat shock protein 27 (HSP27) as a potential mediator of COL11A1-induced cisplatin resistance. Through receptor knockdown and inhibitor experiments, we demonstrated that COL11A1 significantly upregulates HSP27 phosphorylation and expression via DDR2/integrin α1β1 and Src/Akt signaling in ovarian cancer cells. Furthermore, genetic knockdown and pharmacological inhibition of HSP27, via ivermectin treatment, significantly sensitizes ovarian cancer cells cultured on COL11A1 to cisplatin treatment. HSP27 knockdown or inhibition also decreases NFκB activity as well as the expression of inhibitors of apoptosis proteins (IAPs), which are known downstream effector molecules of COL11A1 that promote cisplatin resistance. Interestingly, HSP27 knockdown or inhibition stimulates ovarian cancer cells to upregulate fatty acid oxidation (FAO) for survival and cisplatin resistance, and dual inhibition of HSP27 and FAO synergistically kills ovarian cancer cells that are cultured on COL11A1. Collectively, this study identifies HSP27 as a novel and druggable COL11A1 downstream effector molecule that may be targeted to overcome cisplatin resistance in recurrent ovarian cancer, which often overexpress COL11A1.

Renal fibrosis leads to chronic kidney disease, which affects over 15% of the U.S. population. PAI‐1 is highly upregulated in the tubulointerstitial compartment in several common nephropathies and PAI‐1 global ablation affords protection from fibrogenesis in mice. The precise contribution of renal tubular PAI‐1 induction to disease progression, however, is unknown and surprisingly, appears to be independent of uPA inhibition. Human renal epithelial (HK‐2) cells engineered to stably overexpress PAI‐1 underwent dedifferentiation (E‐cadherin loss, gain of vimentin), G2/M growth arrest (increased p‐Histone3, p21), and robust induction of fibronectin, collagen‐1, and CCN2. These cells are also susceptible to apoptosis (elevated cleaved caspase‐3, annexin‐V positivity) compared to vector controls, demonstrating a previously unknown role for PAI‐1 in tubular dysfunction. Persistent PAI‐1 expression results in a loss of klotho expression, p53 upregulation, and increases in TGF‐βRI/II levels and SMAD3 phosphorylation. Ectopic restoration of klotho in PAI‐1‐transductants attenuated fibrogenesis and reversed the proliferative defects, implicating PAI‐1 in klotho loss in renal disease. Genetic suppression of p53 reversed the PA1‐1‐driven maladaptive repair, moreover, confirming a pathogenic role for p53 upregulation in this context and uncovering a novel role for PAI‐1 in promoting renal p53 signaling. TGF‐βRI inhibition also attenuated PAI‐1‐initiated epithelial dysfunction, independent of TGF‐β1 ligand synthesis. Thus, PAI‐1 promotes tubular dysfunction via klotho reduction, p53 upregulation, and activation of the TGF‐βRI‐SMAD3 axis. Since klotho is an upstream regulator of both PAI‐1‐mediated p53 induction and SMAD3 signaling, targeting tubular PAI‐1 expression may provide a novel, multi‐level approach to the therapy of CKD.