Periodic Reporting for period 4 - SelectiveTGFb-inhib (Pro-tumorigenic effects of TGFb - elucidation of mechanisms and development of selective inhibitors)
Berichtszeitraum: 2023-05-01 bis 2023-10-31
What is the problem/issue being addressed?
The multifunctional cytokine transforming growth factor-beta (TGFbeta) has important functions during the embryonal development and in tissue homeostasis. In cancer, TGFbeta has been found to have tumor suppressive activities at early stages of tumor development, e.g. induction of growth arrest and apoptosis. However, in advanced cancers, TGFbeta is often overexpressed and have tumor promoting activities, e.g. stimulation of epithelial-mesenchymal transition (EMT) of cancer cells which promotes invasiveness and metastasis, stimulation of angiogenesis and inhibition of the immune system. TGFbeta inhibitors may thus be useful for treatment of advanced cancer.
Why is it important for society?
About 50% of people in the Western world will get a cancer diagnosis during their life time and currently about 25% die from cancer. Improvements in cancer diagnosis and treatments have been and are being made, but additional improvements are of utmost importance.
What are the overall objectives?
Our aim has been to elucidate the mechanisms for the pro-tumorigenic effects of TGFbeta and to develop inhibitors that selectively inhibit such pathways, leaving the tumor suppressive pathways unperturbed. In the longer perspective, we hope to identify new methods for treatment of patients with advanced cancer. Since complete inhibition of TGFbeta may promote tumorigenesis and has been found to have severe side effects, it is necessary to develop selective TGFbeta inhibitors.
The multifunctional cytokine transforming growth factor-beta (TGFbeta) has important functions during the embryonal development and in tissue homeostasis. In cancer, TGFbeta has been found to have tumor suppressive activities at early stages of tumor development, e.g. induction of growth arrest and apoptosis. However, in advanced cancers, TGFbeta is often overexpressed and have tumor promoting activities, e.g. stimulation of epithelial-mesenchymal transition (EMT) of cancer cells which promotes invasiveness and metastasis, stimulation of angiogenesis and inhibition of the immune system. TGFbeta inhibitors may thus be useful for treatment of advanced cancer.
Why is it important for society?
About 50% of people in the Western world will get a cancer diagnosis during their life time and currently about 25% die from cancer. Improvements in cancer diagnosis and treatments have been and are being made, but additional improvements are of utmost importance.
What are the overall objectives?
Our aim has been to elucidate the mechanisms for the pro-tumorigenic effects of TGFbeta and to develop inhibitors that selectively inhibit such pathways, leaving the tumor suppressive pathways unperturbed. In the longer perspective, we hope to identify new methods for treatment of patients with advanced cancer. Since complete inhibition of TGFbeta may promote tumorigenesis and has been found to have severe side effects, it is necessary to develop selective TGFbeta inhibitors.
We have identified a pro-tumorigenic cooperation between TGFbeta-SMAD signaling and epidermal growth factor (EGF) signaling in breast cancer cells, involving activator protein (AP)-1 transcription factors and the deltaN isoform of the transcriptional regulator p63 (deltaNp63). AP-1 and deltaNp63 promote the recruitment of SMAD2/3 to several genes encoding proteins involved in cell migration and invasion, including ITGA2, LAMB3 and WNT7A/B. These findings are of importance for breast cancer patients with activated EGF signaling.
deltaNp63 has been shown to be an oncogene. We have shown that the pro-tumorigenic effect of Np63 in TGFbeta signaling is related to its ability to act as a pioneering transcription factor, facilitating the binding of other transcription factors to certain gene promoters.
The TGFbeta family of cytokines also contains members of the bone morphogenetic protein (BMP) subfamily. We found that overactivity of BMPs drives the progression of ovarian and endometrial cancers via induction of EMT and stemness. The mechanism involves induction of a receptor in the TNF receptor family, designated FN14 (encoded by the TNFRSF12A gene). The commonly used chemotherapeutical agent carboplatin induced BMP expression, suggesting that a combination of carboplatin and BMP receptor kinase inhibitors may be useful in the treatment of patients with gynecological cancers.
In collaboration with Maréne Landström at Umeå University, we have found that the type I receptor for TGFbeta (TbetaRI) upon ligand binding undergoes dual proteolytic cleavage, leading to release of the intracellular domain (TbetaRI-ICD), which is then translocated to the nucleus where it drives an invasiveness program. We found that TbetaRI-ICD also interacts with the kinase AURKB and regulates mitosis and cytokinesis. This finding suggests another possible mechanism by which TbetaRI-ICD promotes tumorigenesis, in addition to inducing several genes driving tumor cell invasion. We have found that inhibition of TbetaRI cleavage inhibits metastasis in a mouse model. This finding is of potential clinical importance.
Src is a well-known oncoprotein, which we and others have shown to be activated by TGF stimulation. We have elucidated the molecular mechanism for TGFbeta activation of Src. In short, before TGFbeta binding to its receptors, the type II TGFbeta receptor (TbetaRII) binds Src in an inactive form. After TGFbeta binding, TbetaRII phosphorylates TbetaRI on Tyr182 making it possible for the SH2 domain of Src to bind to this epitope, thereby opening up the conformation of Src which activates its kinase. Interactions between the SH3 domain of Src with a proline-rich region in TbetaRI contributes to the activation of Src. Thereafter, Src phosphorylates several tyrosine residues in TbetaRI and other substrates. We are now elucidating the role of Src in TGF receptor signaling and trafficking.
In order to investigate the mechanism by which TGFbeta induces EMT, we have, in collaboration with Aristidis Moustakas at our department, established a method to genetically mark tumor cells of epithelial vs mesenchymal character; using this imaging method, we have shown that TGFbeta selects for pro-stemness over pro-invasive phenotypes during EMT.
Looking for posttranslational modifications involved in the regulation of TGFbeta signaling, we have found that the function of the inhibitory Smad7 is enhanced by palmitoylation. In addition, we have noticed that also TbetaRI is palmitoylated, the functional effect of which now is investigated.
deltaNp63 has been shown to be an oncogene. We have shown that the pro-tumorigenic effect of Np63 in TGFbeta signaling is related to its ability to act as a pioneering transcription factor, facilitating the binding of other transcription factors to certain gene promoters.
The TGFbeta family of cytokines also contains members of the bone morphogenetic protein (BMP) subfamily. We found that overactivity of BMPs drives the progression of ovarian and endometrial cancers via induction of EMT and stemness. The mechanism involves induction of a receptor in the TNF receptor family, designated FN14 (encoded by the TNFRSF12A gene). The commonly used chemotherapeutical agent carboplatin induced BMP expression, suggesting that a combination of carboplatin and BMP receptor kinase inhibitors may be useful in the treatment of patients with gynecological cancers.
In collaboration with Maréne Landström at Umeå University, we have found that the type I receptor for TGFbeta (TbetaRI) upon ligand binding undergoes dual proteolytic cleavage, leading to release of the intracellular domain (TbetaRI-ICD), which is then translocated to the nucleus where it drives an invasiveness program. We found that TbetaRI-ICD also interacts with the kinase AURKB and regulates mitosis and cytokinesis. This finding suggests another possible mechanism by which TbetaRI-ICD promotes tumorigenesis, in addition to inducing several genes driving tumor cell invasion. We have found that inhibition of TbetaRI cleavage inhibits metastasis in a mouse model. This finding is of potential clinical importance.
Src is a well-known oncoprotein, which we and others have shown to be activated by TGF stimulation. We have elucidated the molecular mechanism for TGFbeta activation of Src. In short, before TGFbeta binding to its receptors, the type II TGFbeta receptor (TbetaRII) binds Src in an inactive form. After TGFbeta binding, TbetaRII phosphorylates TbetaRI on Tyr182 making it possible for the SH2 domain of Src to bind to this epitope, thereby opening up the conformation of Src which activates its kinase. Interactions between the SH3 domain of Src with a proline-rich region in TbetaRI contributes to the activation of Src. Thereafter, Src phosphorylates several tyrosine residues in TbetaRI and other substrates. We are now elucidating the role of Src in TGF receptor signaling and trafficking.
In order to investigate the mechanism by which TGFbeta induces EMT, we have, in collaboration with Aristidis Moustakas at our department, established a method to genetically mark tumor cells of epithelial vs mesenchymal character; using this imaging method, we have shown that TGFbeta selects for pro-stemness over pro-invasive phenotypes during EMT.
Looking for posttranslational modifications involved in the regulation of TGFbeta signaling, we have found that the function of the inhibitory Smad7 is enhanced by palmitoylation. In addition, we have noticed that also TbetaRI is palmitoylated, the functional effect of which now is investigated.
Our studies have identified molecular mechanisms by which pro-tumorigenic signals are activated by TGFbeta. For liberation of TbetaRI-ICD and other pro-tumorigenic pathways, e.g. Src, the mechanisms we have elucidated have paved the way for the development of selective inhibitors.