Development and validation of a phosphorylated SMAD ex vivo stimulation assay

ALK5/VEGFR2 dual inhibitor TU2218 alone or in combination with immune checkpoint inhibitors enhances immune-mediated antitumor effects

Transforming growth factor β (TGFβ) is present in blood of patients who do not respond to anti-programmed cell death (ligand) 1 [PD-(L)1] treatment, and through synergy with vascular endothelial growth factor (VEGF), it helps to create an environment that promotes tumor immune evasion and immune tolerance. Therefore, simultaneous inhibition of TGFβ/VEGF is more effective than targeting TGFβ alone. In this study, the dual inhibitory mechanism of TU2218 was identified through in vitro analysis mimicking the tumor microenvironment, and its antitumor effects were analyzed using mouse syngeneic tumor models. TU2218 directly restored the activity of damaged cytotoxic T lymphocytes (CTLs) and natural killer cells inhibited by TGFβ and suppressed the activity and viability of regulatory T cells. The inactivation of endothelial cells induced by VEGF stimulation was completely ameliorated by TU2218, an effect not observed with vactosertib, which inhibits only TGFβ signaling. The combination of TU2218 and anti-PD1 therapy had a significantly greater antitumor effect than either drug alone in the poorly immunogenic B16F10 syngeneic tumor model. The mechanism of tumor reduction was confirmed by flow cytometry, which showed upregulated VCAM-1 expression in vascular cells and increased influx of CD8 + CTLs into the tumor. As another strategy, combination of anti-CTLA4 therapy and TU2218 resulted in high complete regression (CR) rates in CT26 and WEHI-164 tumor models. In particular, immunological memory generated by the combination of anti-CTLA4 and TU2218 in the CT26 model prevented the development of tumors after additional tumor cell transplantation, suggesting that the TU2218-based combination has therapeutic potential in immunotherapy.

Targeting transforming growth factor beta signaling in metastatic osteosarcoma

Osteosarcoma is a rare type of bone cancer, and half of the cases affect children and adolescents younger than 20 years of age. Despite intensive efforts to improve both chemotherapeutics and surgical management, the clinical outcome for metastatic osteosarcoma remains poor. Transforming growth factor β (TGF-β) is one of the most abundant growth factors in bones. The TGF-β signaling pathway has complex and contradictory roles in the pathogenesis of human cancers. TGF-β is primarily a tumor suppressor that inhibits proliferation and induces apoptosis of premalignant epithelial cells. In the later stages of cancer progression, however, TGF-β functions as a metastasis promoter by promoting tumor growth, inducing epithelial-mesenchymal transition (EMT), blocking antitumor immune responses, increasing tumor-associated fibrosis, and enhancing angiogenesis. In contrast with the dual effects of TGF-β on carcinoma (epithelial origin) progression, TGF-β seems to mainly have a pro-tumoral effect on sarcomas including osteosarcoma (mesenchymal origin). Many drugs that target TGF-β signaling have been developed: neutralizing antibodies that prevent TGF-β binding to receptor complexes; ligand trap employing recombinant Fc-fusion proteins containing the soluble ectodomain of either type II (TβRII) or the type III receptor ((TβRIII), preventing TGF-β from binding to its receptors; antisense nucleotides that reduce TGF-β expression at the transcriptional/translational level; small molecule inhibitors of serine/threonine kinases of the type I receptor (TβRI) preventing downstream signaling; and vaccines that contain cell lines transfected with TβRII antisense genes, or target furin convertase, resulting in reduced TGF-β signaling. TGF-β antagonists have been shown to have effects on osteosarcoma in vitro and in vivo. One of the small molecule TβRI inhibitors, Vactosertib, is currently undergoing a phase 1/2 clinical trial to evaluate its effect on osteosarcoma. Several phase 1/2/3 clinical trials have shown TGF-β antagonists are safe and well tolerated. For instance, Luspatercept, a TGF-β ligand trap, has been approved by the FDA for the treatment of anemia associated with myeloid dysplastic syndrome (MDS) with ring sideroblasts/mutated SF3B1 with acceptable safety. Clinical trials evaluating the long-term safety of Luspatercept are in process.

TGF-β inhibitor treatment of H₂O₂-induced cystitis models provides biochemical mechanism for elucidating interstitial cystitis/painful bladder syndrome patients

Interstitial cystitis/painful bladder syndrome (IC/PBS) is a chronic disease for which no effective treatment is available. Transforming growth factor-β (TGF-β) is thought to be involved in the pathogenesis of IC/PBS, and previous studies have suggested that administrations of a TGF-β inhibitor significantly ameliorated IC/PBS in a mouse model. However, the molecular mechanisms underlying the therapeutic effect of a TGF-b inhibitor on IC/PBS has not been comprehensively analyzed. TGF-β has a variety of actions, such as regulation of immune cells and fibrosis. In our study, we induced IC/PBS-like disease in mice by an intravesical administration of hydrogen peroxide (H₂O₂) and examined the effects of three TGF-β inhibitors, Repsox, SB431542, and SB505124, on the urinary functions as well as histological and gene expression profiles in the bladder. TGF-β inhibitor treatment improved urinary function and histological changes in the IC/PBS mouse model, and SB431542 was most effective among the TGF-β inhibitors. In our present study, TGF-β inhibitor treatment improved abnormal enhancement of nociceptive mechanisms, immunity and inflammation, fibrosis, and dysfunction of bladder urothelium. These results show that multiple mechanisms are involved in the improvement of urinary function by TGF-β inhibitor.

A Phase Ib Trial of AVID200, a TGFβ 1/3 Trap, in Patients with Myelofibrosis

PURPOSE

Myelofibrosis (MF) is a clonal myeloproliferative neoplasm characterized by systemic symptoms, cytopenias, organomegaly, and bone marrow fibrosis. JAK2 inhibitors afford symptom and spleen burden reduction but do not alter the disease course and frequently lead to thrombocytopenia. TGFβ, a pleiotropic cytokine elaborated by the MF clone, negatively regulates normal hematopoiesis, downregulates antitumor immunity, and promotes bone marrow fibrosis. Our group previously showed that AVID200, a potent and selective TGFβ 1/3 trap, reduced TGFβ1-induced proliferation of human mesenchymal stromal cells, phosphorylation of SMAD2, and collagen expression. Moreover, treatment of MF mononuclear cells with AVID200 led to increased numbers of progenitor cells (PC) with wild-type JAK2 rather than JAK2V617F.

PATIENTS AND METHODS

We conducted an investigator-initiated, multicenter, phase Ib trial of AVID200 monotherapy in 21 patients with advanced MF.

RESULTS

No dose-limiting toxicity was identified at the three dose levels tested, and grade 3/4 anemia and thrombocytopenia occurred in 28.6% and 19.0% of treated patients, respectively. After six cycles of therapy, two patients attained a clinical benefit by IWG-MRT criteria. Spleen and symptom benefits were observed across treatment cycles. Unlike other MF-directed therapies, increases in platelet counts were noted in 81% of treated patients with three patients achieving normalization. Treatment with AVID200 resulted in potent suppression of plasma TGFβ1 levels and pSMAD2 in MF cells.

CONCLUSIONS

AVID200 is a well-tolerated, rational, therapeutic agent for the treatment of patients with MF and should be evaluated further in patients with thrombocytopenic MF in combination with agents that target aberrant MF intracellular signaling pathways.

Transforming growth factor β latency: A mechanism of cytokine storage and signalling regulation in liver homeostasis and disease

Transforming growth factor-β (TGF-β) is a potent effector in the liver, which is involved in a plethora of processes initiated upon liver injury. TGF-β affects parenchymal, non-parenchymal, and inflammatory cells in a highly context-dependent manner. Its bioavailability is critical for a fast response to various insults. In the liver – and probably in other organs – this is made possible by the deposition of a large portion of TGF-β in the extracellular matrix as an inactivated precursor form termed latent TGF-β (L-TGF-β). Several matrisomal proteins participate in matrix deposition, latent complex stabilisation, and activation of L-TGF-β. Extracellular matrix protein 1 (ECM1) was recently identified as a critical factor in maintaining the latency of deposited L-TGF-β in the healthy liver. Indeed, its depletion causes spontaneous TGF-β signalling activation with deleterious effects on liver architecture and function. This review article presents the current knowledge on intracellular L-TGF-β complex formation, secretion, matrix deposition, and activation and describes the proteins and processes involved. Further, we emphasise the therapeutic potential of toning down L-TGF-β activation in liver fibrosis and liver cancer.

Targeting TGFβ signal transduction for cancer therapy

Transforming growth factor-β (TGFβ) family members are structurally and functionally related cytokines that have diverse effects on the regulation of cell fate during embryonic development and in the maintenance of adult tissue homeostasis. Dysregulation of TGFβ family signaling can lead to a plethora of developmental disorders and diseases, including cancer, immune dysfunction, and fibrosis. In this review, we focus on TGFβ, a well-characterized family member that has a dichotomous role in cancer progression, acting in early stages as a tumor suppressor and in late stages as a tumor promoter. The functions of TGFβ are not limited to the regulation of proliferation, differentiation, apoptosis, epithelial-mesenchymal transition, and metastasis of cancer cells. Recent reports have related TGFβ to effects on cells that are present in the tumor microenvironment through the stimulation of extracellular matrix deposition, promotion of angiogenesis, and suppression of the anti-tumor immune reaction. The pro-oncogenic roles of TGFβ have attracted considerable attention because their intervention provides a therapeutic approach for cancer patients. However, the critical function of TGFβ in maintaining tissue homeostasis makes targeting TGFβ a challenge. Here, we review the pleiotropic functions of TGFβ in cancer initiation and progression, summarize the recent clinical advancements regarding TGFβ signaling interventions for cancer treatment, and discuss the remaining challenges and opportunities related to targeting this pathway. We provide a perspective on synergistic therapies that combine anti-TGFβ therapy with cytotoxic chemotherapy, targeted therapy, radiotherapy, or immunotherapy.

Analytical Characterization of an Enzyme-Linked Immunosorbent Assay for the Measurement of Transforming Growth Factor β1 in Human Plasma

Background

The transforming growth factor β (TGF-β)–signaling pathway has emerged as a promising therapeutic target for many disease states including hepatocellular carcinoma (HCC). Because of the pleiotropic effects of this pathway, patient selection and monitoring may be important. TGF-β1 is the most prevalent isoform, and an assay to measure plasma levels of TGF-β1 would provide a rational biomarker to assist with patient selection. Therefore, the objective of this study was to analytically validate a colorimetric ELISA for the quantification of TGF-β1 in human plasma.

Methods

A colorimetric sandwich ELISA for TGF-β1 was analytically validated per Clinical and Laboratory Standards Institute protocols by assessment of precision, linearity, interfering substances, and stability. A reference range for plasma TGF-β1 was established for apparently healthy individuals and potential applicability was demonstrated in HCC patients.

Results

Precision was assessed for samples ranging from 633 to 10822 pg/mL, with total variance ranging from 28.4% to 7.2%. The assay was linear across the entire measuring range, and no interference of common blood components or similar molecules was observed. For apparently healthy individuals, the average TGF-β1 level was 1985 ± 1488 pg/mL compared to 4243 ± 2003 pg/mL for HCC patients. Additionally, the TGF-β1 level in plasma samples was demonstrated to be stable across all conditions tested, including multiple freeze–thaw cycles.

Conclusions

The ELISA described in this report is suitable for the quantification of TGF-β1 in human plasma and for investigational use in an approved clinical study.

Preclinical assessment of galunisertib (LY2157299 monohydrate), a first-in-class transforming growth factor-β receptor type I inhibitor

Transforming growth factor-β (TGFβ) is an important driver of tumor growth via intrinsic and extrinsic mechanisms, and is therefore an attractive target for developing cancer therapeutics. Using preclinical models, we characterized the anti-tumor activity of a small molecule inhibitor of TGFβ receptor I (TGFβRI), galunisertib (LY2157299 monohydrate). Galunisertib demonstrated potent and selective inhibition of TGFβRI with corresponding inhibition of downstream signaling via inhibition of SMAD phosphorylation (pSMAD). Galunisertib also inhibited TGFβ-induced pSMAD in vivo, which enabled a pharmacokinetic/pharmacodynamic profile in Calu6 and EMT6-LM2 tumors. Galunisertib demonstrated anti-tumor activity including inhibition of tumor cell migration and mesenchymal phenotype, reversal of TGFβ-mediated immune-suppression, and tumor growth delay. A concentration-effect relationship was established with a dosing schedule to achieve the optimal level of target modulation. Finally, a rat model demonstrated a correlation between galunisertib-dependent inhibition of pSMAD in tumor tissues and in PBMCs, supporting the use of PBMCs for assessing pharmacodynamic effects. Galunisertib has been tested in several clinical studies with evidence of anti-tumor activity observed in subsets of patients. Here, we demonstrate that galunisertib inhibits a number of TGFβ-dependent functions leading to anti-tumor activity. The enhanced understanding of galunisertib provides rationale for further informed clinical development of TGFβ pathway inhibitors.

In the Shadow of Fibrosis: Innate Immune Suppression Mediated by Transforming Growth Factor-β

Transforming growth factor-β (TGFB) regulates cell proliferation, differentiation, apoptosis, and matrix homeostasis and is intimately involved in fibrosis. TGFB expression is increased in fibrotic lung diseases, such as idiopathic pulmonary fibrosis, and in chronic inflammatory conditions, such as chronic obstructive pulmonary disease and asthma. In addition to exhibiting profibrotic activities, the protein exhibits profound immune-suppressive actions involving both innate and adaptive responses, but often this aspect of TGFB biology is overlooked. Recent investigations have demonstrated that TGFB causes wide-ranging immune suppression, including blunting of pivotal early innate IFN responses. These activities permit severe virus infections, often followed by secondary bacterial infections, which may last longer, with augmented inflammation, scarring, fibrosis, and loss of lung function. Strategies to oppose TGFB actions or to enhance IFN responses may help ameliorate the detrimental consequences of infection in patients with diseases characterized by TGFB overexpression, inflammation, and fibrosis.

Switching Roles of TGF-β in Cancer Development: Implications for Therapeutic Target and Biomarker Studies

TGF-β induces complicated and even opposite responses in numerous biological processes, e.g., tumor suppression in pre-malignant cells and metastasis promotion in cancer cells. However, the cellular contextual determinants of these different TGF-β roles remain elusive, and the driver genes triggering the determinants’ changes have not been identified. Recently, however, several findings have provided new insights on the contextual determinants of Smads in TGF-β’s biological processes. These novel switches and their effectors may serve as prognostic biomarkers and therapeutic targets of TGF-β-mediated cancer progression.

Clinical development of galunisertib (LY2157299 monohydrate), a small molecule inhibitor of transforming growth factor-beta signaling pathway

Transforming growth factor-beta (TGF-β) signaling regulates a wide range of biological processes. TGF-β plays an important role in tumorigenesis and contributes to the hallmarks of cancer, including tumor proliferation, invasion and metastasis, inflammation, angiogenesis, and escape of immune surveillance. There are several pharmacological approaches to block TGF-β signaling, such as monoclonal antibodies, vaccines, antisense oligonucleotides, and small molecule inhibitors. Galunisertib (LY2157299 monohydrate) is an oral small molecule inhibitor of the TGF-β receptor I kinase that specifically downregulates the phosphorylation of SMAD2, abrogating activation of the canonical pathway. Furthermore, galunisertib has antitumor activity in tumor-bearing animal models such as breast, colon, lung cancers, and hepatocellular carcinoma. Continuous long-term exposure to galunisertib caused cardiac toxicities in animals requiring adoption of a pharmacokinetic/pharmacodynamic-based dosing strategy to allow further development. The use of such a pharmacokinetic/pharmacodynamic model defined a therapeutic window with an appropriate safety profile that enabled the clinical investigation of galunisertib. These efforts resulted in an intermittent dosing regimen (14 days on/14 days off, on a 28-day cycle) of galunisertib for all ongoing trials. Galunisertib is being investigated either as monotherapy or in combination with standard antitumor regimens (including nivolumab) in patients with cancer with high unmet medical needs such as glioblastoma, pancreatic cancer, and hepatocellular carcinoma. The present review summarizes the past and current experiences with different pharmacological treatments that enabled galunisertib to be investigated in patients.

Pharmacokinetic, pharmacodynamic and biomarker evaluation of transforming growth factor-β receptor I kinase inhibitor, galunisertib, in phase 1 study in patients with advanced cancer

Purpose Transforming growth factor-beta (TGF-β) signaling plays a key role in epithelial-mesenchymal transition (EMT) of tumors, including malignant glioma. Small molecule inhibitors (SMI) blocking TGF-β signaling reverse EMT and arrest tumor progression. Several SMIs were developed, but currently only LY2157299 monohydrate (galunisertib) was advanced to clinical investigation. Design The first-in-human dose study had three parts (Part A, dose escalation, n = 39; Part B, safety combination with lomustine, n = 26; Part C, relative bioavailability study, n = 14). Results A preclinical pharmacokinetic/pharmacodynamic (PK/PD) model predicted a therapeutic window up to 300 mg/day and was confirmed in Part A after continuous PK/PD. PK was not affected by co-medications such as enzyme-inducing anti-epileptic drugs or proton pump inhibitors. Changes in pSMAD2 levels in peripheral blood mononuclear cells were associated with exposure indicating target-related pharmacological activity of galunisertib. Twelve (12/79; 15%) patients with refractory/relapsed malignant glioma had durable stable disease (SD) for 6 or more cycles, partial responses (PR), or complete responses (CR). These patients with clinical benefit had high plasma baseline levels of MDC/CCL22 and low protein expression of pSMAD2 in their tumors. Of the 5 patients with IDH1/2 mutation, 4 patients had a clinical benefit as defined by CR/PR and SD ≥6 cycles. Galunisertib had a favorable toxicity profile and no cardiac adverse events. Conclusion Based on the PK, PD, and biomarker evaluations, the intermittent administration of galunisertib at 300 mg/day is safe for future clinical investigation.

Targeting the TGFβ signalling pathway in disease

Many drugs that target transforming growth factor-β (TGFβ) signalling have been developed, some of which have reached Phase III clinical trials for a number of disease applications. Preclinical and clinical studies indicate the utility of these agents in fibrosis and oncology, particularly in augmentation of existing cancer therapies, such as radiation and chemotherapy, as well as in tumour vaccines. There are also reports of specialized applications, such as the reduction of vascular symptoms of Marfan syndrome. Here, we consider why the TGFβ signalling pathway is a drug target, the potential clinical applications of TGFβ inhibition, the issues arising with anti-TGFβ therapy and how these might be tackled using personalized approaches to dosing, monitoring of biomarkers as well as brief and/or localized drug-dosing regimens.

PKCalpha-induced drug resistance in pancreatic cancer cells is associated with transforming growth factor-beta1

Background

Drug resistance remains a great challenge in the treatment of pancreatic cancer. The goal of this study was to determine whether TGF-β1 is associated with drug resistance in pancreatic cancer.

Methods

Pancreatic cancer BxPC3 cells were stably transfected with TGF-β1 cDNA. Cellular morphology and cell cycle were determined and the suppressive subtracted hybridization (SSH) assay was performed to identify differentially expressed genes induced by TGF-β1. Western blotting and immunohistochemistry were used to detect expression of TGF-β1-related genes in the cells and tissue samples. After that, the cells were further treated with an anti-cancer drug (e.g., cisplatin) after pre-incubated with the recombinant TGF-β1 plus PKCα inhibitor Gö6976. TGF-β1 type II receptor, TβRII was also knocked down using TβRII siRNA to assess the effects of these drugs in the cells. Cell viability was assessed by MTT assay.

Results

Overexpression of TGF-β1 leads to a markedly increased invasion potential but a reduced growth rate in BxPC3 cells. Recombinant TGF-β1 protein increases expression of PKCα in BxPC3 cells, a result that we confirmed by SSH. Moreover, TGF-β1 reduced the sensitivity of BxPC3 cells to cisplatin treatment, and this was mediated by upregulation of PKCα. However, blockage of PKCα with Gö6976 and TβRII with siRNA reversed the resistance of BxPC3 cells to gemcitabine, even in the presence of TGF-β1. Immunohistochemical data show that pancreatic cancers overexpress TGF-β1 and P-gp relative to normal tissues. In addition, TGF-β1 expression is associated with P-gp and membranous PKCα expression in pancreatic cancer.

Conclusions

TGF-β1-induced drug resistance in pancreatic cancer cells was associated with PKCα expression. The PKCα inhibitor Gö6976 could be a promising agent to sensitize pancreatic cancer cells to chemotherapy.

Transforming growth factor-beta signaling: emerging stem cell target in metastatic breast cancer?

In most human breast cancers, lowering of TGFbeta receptor- or Smad gene expression combined with increased levels of TGFbetas in the tumor microenvironment is sufficient to abrogate TGFbetas tumor suppressive effects and to induce a mesenchymal, motile and invasive phenotype. In genetic mouse models, TGFbeta signaling suppresses de novo mammary cancer formation but promotes metastasis of tumors that have broken through TGFbeta tumor suppression. In mouse models of "triple-negative" or basal-like breast cancer, treatment with TGFbeta neutralizing antibodies or receptor kinase inhibitors strongly inhibits development of lung- and bone metastases. These TGFbeta antagonists do not significantly affect tumor cell proliferation or apoptosis. Rather, they de-repress anti-tumor immunity, inhibit angiogenesis and reverse the mesenchymal, motile, invasive phenotype characteristic of basal-like and HER2-positive breast cancer cells. Patterns of TGFbeta target genes upregulation in human breast cancers suggest that TGFbeta may drive tumor progression in estrogen-independent cancer, while it mediates a suppressive host cell response in estrogen-dependent luminal cancers. In addition, TGFbeta appears to play a key role in maintaining the mammary epithelial (cancer) stem cell pool, in part by inducing a mesenchymal phenotype, while differentiated, estrogen receptor-positive, luminal cells are unresponsive to TGFbeta because the TGFBR2 receptor gene is transcriptionally silent. These same cells respond to estrogen by downregulating TGFbeta, while antiestrogens act by upregulating TGFbeta. This model predicts that inhibiting TGFbeta signaling should drive the differentiation of mammary stem cells into ductal cells. Consequently, TGFbeta antagonists may convert basal-like or HER2-positive cancers to a more epithelioid, non-proliferating (and, perhaps, non-metastatic) phenotype. Conversely, these agents might antagonize the therapeutic effects of anti-estrogens in estrogen-dependent luminal cancers. These predictions need to be addressed prospectively in clinical trials and should inform the selection of patient populations most likely to benefit from this novel anti-metastatic therapeutic approach.

TGF-beta signalling-related markers in cancer patients with bone metastasis

We measured transforming growth factor (TGF)-beta-dependent biomarkers in plasma and in peripheral blood mononuclear cells (PBMCs) to identify suitable pharmacodynamic markers for future clinical trials with TGF-beta inhibitors. Forty-nine patients with bone metastasis were enrolled in the study, including patients with breast (n=23) and prostate cancer (n=15). Plasma TGF-beta1 levels were elevated in more than half of the cancer patients (geometric mean 2.63 ng ml(-1)) and positively correlated with increased platelet factor 4 (PF4) levels, parathyroid-related protein (PTHrP), von Willebrand Factor (vWF) and interleukin (IL)-10. PBMC were stimulated ex vivo to determine the individual biological variability of an ex vivo assay measuring pSMAD expression. This assay performed sufficiently well to allow its future use in a clinical trial of a TGF-beta inhibitor.