Cancer is a disease that involves aggressive changes in the genome and aberrant signals between the living cells. Signalling pathways such as TGF-β (Transforming growth factor-β), Wnt, EGF (epidermal growth factor) and HIF (Hypoxia-inducible factor) evolved to regulate growth and development in mammals. These factors are also implicated for tumorigenesis due to failure or aberrant expression of components in these pathways. Cancer progression is a multistep process, and these steps reflect genetic alterations driving the progressive transformation of healthy human cells into highly malignant derivatives. Many types of cancers are diagnosed in the human population, such as head & neck, cervical, brain, liver, colon, prostate, uterine, breast, and renal cell cancer.

Prostate cancer is the second most common cancer and one of the foremost leading cancer-related deaths in men in the world. Aberrant Wnt3a signals promote cancer progression through the accumulation of β-Catenin. In the first paper, we have elucidated intriguing functions for Tumour necrosis factor receptor-associated factor 6 (TRAF6) as a coregulatory factor for the expression of Wnt-target genes which was confirmed in vivo by using CRISPR/Cas9 genomic editing, in zebrafish. Our data suggest that Wnt3a promotes TRAF6 interaction with Wnt components, and TRAF6 is required for gene expression of β-Catenin as well as for the Wnt-ligand co-receptor LRP5. From the in vivo studies, we elucidated positive regulation of TRAF6, which is crucial for survival and development of zebrafish. This study identifies TRAF6 as an evolutionary conserved co-regulatory protein in the Wnt pathway that also promotes the progression of prostate and colorectal cancer due to its positive effects on Wnt3a signalling.

Hypoxia is a condition due to O₂ deprivation, and Hypoxia-inducible factors (HIF) transcription factors are responsible for the maintenance of oxygen homeostasis in living cells. Irregularities in these HIF transcription factors trigger pathological cellular responses for initiation and progression of malignant cancers. Renal cell carcinoma, malignant cancer arising in renal parenchyma and renal pelvis and, hypoxia plays a vital role in its progression. In the second paper, we have investigated the clinicopathological relevance of several hypoxic and TGF-β component proteins such as HIF-1α/2α/3α, TGF-β type 1 receptor (ALK5-FL) and the intracellular domain of ALK5 (ALK5-ICD), SNAI1 and PAI-1 with patient survival in clear cell renal cell carcinoma (ccRCC). We showed that HIF-2α associated with low cancer-specific survival. HIF-2α and SNAI1 positively correlated with ALK5-ICD, pSMAD2/3, PAI-1 and SNAI1 with HIF-2α; HIF-1α positively correlated with pSMAD2/3. Further, under normoxic conditions, our data suggest that ALK5 interacts with HIF-1α and HIF-2α, and promotes their expression and target genes such as GLUT1 and CA9, in a VHL dependent manner through its kinase activity. These findings shed light on the critical aspect of cross-talk between TGF-β signalling and hypoxia pathway, and also the novel finding of an interaction between ALK5 and HIF-α might provide a more in-depth understanding of mechanisms behind tumour progression

In the third paper, an ongoing study, we investigated the role of HIF-3α in the progression of Renal cell carcinoma and its association with the components of TGF-β and HIF pathways. We have observed increased levels of HIF-3α in ccRCC and pRCC (papillary renal cell carcinoma) which are associated with advanced tumour stage, metastasis and larger tumours. Also, we found HIF-3α show a significant positive association with pro-invasive gene SNAI1, which is a crucial regulator of epithelial to mesenchymal transition. TRAF6 an E3 ligase known to be a prognostic marker in RCC and we observed HIF-3α associates with TRAF6.

Renal cell carcinoma (RCC) is the cancer of the kidneys; about 1100 patients with RCC are diagnosed in Sweden each year. RCC can be classified into several subtypes, clear cell renal cell carcinoma (ccRCC) is most common accounting to about 70% of all RCCs, and also the most lethal; papillary renal cell carcinoma (pRCC) accounts to about 10%‐15%, while chromophobe renal cell carcinoma (chRCC) accounts to about 5% of all RCCs. There is a need to study the distinguishing features of RCC subtypes to design treatment. Von Hippel‐Lindau tumor suppressor gene (VHL) is often inactivated in ccRCC, unlike in pRCC or chRCC. Transforming growth factor‐β (TGF‐β) is a cytokine involved in various biological processes such as differentiation, proliferation, apoptosis, migration, andepithelial‐mesenchymal transition. TGF‐β exerts its functions through canonical (Smad‐dependent) and non‐canonical (Smadindependent) signaling pathways. In the first study, we have shown that both canonical and non‐canonical TGF‐β signaling pathways are associated with ccRCC tumor progression. VHL is known to have a dampening effect on TGF‐β signaling in RCC. However, the effects of pVHL status on the TGF‐β signaling pathway in ccRCC and non-ccRCC has not yet been studied in detail. In the second study, we have investigated the effects of the TGF‐β signaling pathway in the presence or absence of pVHL in ccRCC and non‐ccRCC. We show that, in ccRCC, VHL has an inhibiting effect exclusively on canonical TGF‐β signaling, and has no effect on non‐canonical TGF‐β signaling via ALK5‐ICD. In non‐ccRCC, TGF‐β signaling did not have an effect on tumor progression. Further, we demonstrate that VHL, through its ubiquitin ligases activity ubiquitinates ALK5 in a K48 dependent manner and subjects it to proteasomal degradation. During the normoxic conditions, VHL is implicated in ubiquitination and proteasomal degradation of Hypoxia‐inducible factors (HIFs). In hypoxic conditions or when the loss of VHL occurs, HIFs accumulates in the cytoplasm and enters the nucleus to initiate angiogenesis, cell proliferation, and tumor progression. In the third study, we have explored a potential synergistic cross‐talk between TGF‐β signaling and hypoxia in ccRCC. We demonstrate a correlation between TGF‐β signaling components and HIF‐1α/2α in ccRCC. We have also shown that TGF‐β signaling enhances the expression of HIF‐1α/2α and their target genes even under normoxic conditions, dependent on the kinase activity of ALK5 and dictated by the status of VHL. We present novel data that the synergistic crosstalk between hypoxia and TGF‐β is orchestrated through interactions between ALK5 and HIF‐1α/2α. HIF‐3α is only limited studied, compared with HIF‐1α and HIF‐2α. In the fourth study, we have analyzed the roles of HIF‐3α in ccRCC and pRCC and show that HIF‐3α is associated with advanced stage and metastasized tumors. We also found that HIF‐3α is associated with TRAF6, a crucial component of non‐canonical TGF‐β signaling.