Inhibition of the TGF-beta signaling pathway in tumor cells

Emerging protein kinase inhibitors for the treatment of multiple myeloma

Introduction: Significant advances have been made during the last two decades in terms of new therapeutic options but also of innovative approaches to diagnosis and management of multiple myeloma (MM). While patient survival has been significantly prolonged, most patients relapse. Including the milestone approval of the first kinase inhibitor imatinib mesylate for CML in 2001, 48 small molecule protein kinase (PK) inhibitors have entered clinical practice until now. However, no PK inhibitor has been approved for MM therapy yet. Areas covered: This review article summarizes up-to-date knowledge on the pathophysiologic role of PKs in MM. Derived small molecules targeting receptor tyrosine kinases (RTKs), the Ras/Raf/MEK/MAPK- pathway, the PI3K/Akt/mTOR- pathway as well as Bruton tyrosine kinase (BTK), Aurora kinases (AURK), and cyclin-dependent kinases (CDKs) are most promising. Preclinical as well as early clinical data focusing on these molecules will be presented and critically reviewed. Expert opinion: Current MM therapy is directed against general vulnerabilities. Novel therapeutic strategies, inhibition of PKs in particular, are directed to target tumor-specific driver aberrations such as genetic abnormalities and microenvironment-driven deregulations. Results of ongoing Precision Medicine trials with PK inhibitors alone or in combination with other agents are eagerly awaited and hold the promise of once more improving MM patient outcome.

Association between TGFBR1*6A and osteosarcoma: a Chinese case-control study

Background

TGFBR1*6A is a common hypomorphic variant of transforming growth factor β receptor 1 (TGFBR1). TGFBR1*6A is associated with an increased cancer risk, but the association of this polymorphism with osteosarcoma remains unknown. We have measured the frequency of TGFBR1*6A variants in osteosarcoma cases and controls.

Methods

Our case-control study is based on 168 osteosarcoma patients and 168 age- and gender-matched controls. Blood samples were obtained and the TGFBR1*6A variant determined by PCR amplification and DNA sequencing. The odds ratio (OR) and 95% confidence interval (95% CI) for the TGFBR1*6A polymorphism were calculated by unconditional logistic regression, adjusted for both age and gender. Three models - dominant, additive and recessive - were used to analyze the contribution of the TGFBR1*6A variant to osteosarcoma susceptibility.

Results

Heterozygotic and homozygotic TGFBR1*6A variants represented 50.4% and 6.0% of the 168 cases, whereas the controls had 18. 5% and 1.3%, respectively. ORs for homozygosity and heterozygosity of the TGFBR1*6A allele were 4.6 [95% CI, 2.33-7.97] and 2.9 [95% CI, 1.59-5.34] in the additive model. There were significant increases in the TGFBR1*6A variants in osteosarcoma cases compared to control in all 3 models. Further analysis showed that TGFBR1*6A genotypes were not associated with gender, age, or tumor location. However, TGFBR1*6A was significantly associated with less metastasis.

Conclusions

TGFBR1*6A, a dominant polymorphism of TGFBR1, is associated with increased susceptibility and metastasis spread of osteosarcoma.

Int7G24A variant of transforming growth factor-beta receptor 1 is associated with osteosarcoma susceptibility in a Chinese population

The TGF-beta signaling pathway is important in the development and invasion of cancers. Int7G24A is an intronic variant of TGF-beta receptor type 1 and has been shown to be associated with the occurrence of some kinds of cancers. Nevertheless, the association of this polymorphism with osteosarcoma is unknown. In this study, we evaluated Int7G24A variant frequencies in osteosarcoma cases. The case-control study involved 168 osteosarcoma patients and 168 age- and gender-matched controls. The blood samples were obtained, and Int7G24A variant was determined by PCR amplification and DNA sequencing. The odds ratio (OR) and 95% confidence interval (95% CI) for the Int7G24A polymorphism were calculated using unconditional logistic regression adjusted for age and gender. Three analysis models, which are the dominant model, additive model and recessive model, were used to analyze the contribution of Int7G24A variant to osteosarcoma susceptibility. Heterozygotic and homozygotic Int7G24A variants were 33.93 and 6.55% in total 168 cases, while they were 28.57 and 2.98%, respectively, in total 168 controls. The ORs for homozygosity and heterozygosity of Int7G24A allele were 1.56 [95% CI, 0.98-1.83] and 2.89 [95% CI, 1.46-4.92] in additive model. The ORs of Int7G24A genotypes in dominant model and in recessive model were 1.75 [95% CI, 1.21-2.68] and 2.21 [95% CI, 1.34-4.72], respectively. There were significant increases in Int7G24A variants in osteosarcoma cases when compared to control in every three models. Further analysis showed that Int7G24A genotypes were not associated with gender and osteosarcoma location of the cases. However, Int7G24A was significantly increased in the cases less than 20 years old. Moreover, Int7G24A was significantly associated with increased distant metastasis of osteosarcoma. It is concluded that Int7G24A is a polymorphism of TGFBR1 that is associated with the susceptibility and distant metastasis of osteosarcoma.

Targeting TGF-beta in prostate cancer: therapeutic possibilities during tumor progression

BACKGROUND

TGF-beta regulates prostate growth by inhibiting epithelial cell proliferation and inducing apoptosis through eliciting a dynamic signaling pathway. In metastatic prostate cancer, however, TGF-beta serves as a tumor promoter. TGF-beta engages Smad-dependent and Smad-independent mechanisms to exert its action. During prostate tumorigenesis, prostate cells exhibit loss or mutation of TGF-beta transmembrane receptors. Increased production of TGF-beta causes immunosuppression, extracellular matrix degradation, epithelia to mesenchymal transition and angiogenesis that promotes tumor cell invasion and metastasis.

OBJECTIVE

The molecular basis for effective therapeutic targeting of TGF-beta must be directed towards the double-edge-sword nature of the cytokine: inhibiting the TGF-beta tumor promoter capabilities in advanced metastatic prostate cancer, although retaining the growth-inhibitory abilities exhibited in early stages of prostate tumorigenesis.

RESULTS/CONCLUSION

The current understanding of the therapeutic possibilities of targeting TGF-beta signaling during prostate tumor progression is built on preclinical studies. Studies targeting TGF-beta signaling pathway for the treatment of several human malignancies include the use of neutralizing antibodies, antisense oligonucelotides and small molecule inhibitors of kinase activity of the receptor complex. This review focuses on exploiting the therapeutic potential of targeting TGF-beta signaling in the context of its contribution to prostate cancer initiation and progression to metastasis.