Blood-based liquid biopsy has shown its advantages in clinical settings as a minimally invasive, safe, and alternative or complementary approach for tissue biopsies. Importantly, tumor derived secretomes or cancer degradomes in TME play central roles in tumor progression, recurrence and metastases . While DNA or RNA sequence data have been utilized to guide cancer treatment, a recent study demonstrates that cancer proteome is complement to DNA/RNA status and has the potential to refine treatment options . In addition, proteome-wide depiction of interactomes across cancer and host response at tissue and circulating level remains elusive. Here, we performed a comprehensive analysis of tissue and serum proteomes from PTC patients and healthy controls. We applied a strategy employing antibody microarrays and DIA-MS to quantify a total of 1091 serum proteins that results much improved depth of serum proteome. Integrative analyses reveal that integrin-mediated pathways are at the nexus of crosstalk between blood and tumor and complement activation and coagulation cascades at the circulating level may promote tumor growth. These findings improve our knowledge of thyroid cancer biology and hence potentially aide the clinical decision-making process.
We identified a dysregulation of integrin-mediated pathways underlying blood-tumor crosstalk in PTC patients. This finding adds to recent discussions on the roles of thyroid hormones (THs) on thyroid cancer proliferation, metastasis, angiogenesis, radio-resistance via the integrin which is overexpressed in cancer cells . L-thyroxine (T4) receptor, not T3 receptor, on integrin αvβ3 has been recognized as a principle ligand of the thyroid hormone analogue receptor in cancer cells . It has been demonstrated that the bioactivity of T4 include promoting cancer cell proliferation, migration, angiogenesis and platelet interaction . The underlying mechanism may be the activation of MAPK pathway that promotes papillary and follicular thyroid cancer cell proliferation in response to T4 and inhibition of p53-dependent apoptosis of tumor cells [38, 39]. We also show the dysregulation of MAPK signaling for integrin in PTC patients in our analysis. To be noted that, T4 concentrations of PTC patients are within the reference range in our study. This phenomenon has been shown in a previous study that T4 at physiological concentrations initiates at the iodothyronine receptor on cell surface integrin αvβ3 and activate cancer cell proliferation in vitro and in xenografts .
One other possible T4-related mechanism is the actions on the EMT process . Our analysis based on proteomic data in PTC patients identified EMT markers FN1, GSN and GALE are strongly expressed in PTC tissues and also at the circulating level. We further show that higher expressions of FN1, GSN and GALE in PTC tissues compared to NATs. This finding is consistent to the transcriptional level of FN1, GSN and GALE expressions in TCGA dataset of thyroid cancer. In particular, integrin αvβ3 contains an Arg-Gly-Asp (RGD) recognition binding site specially for ECM proteins such as FN1 and thyroid hormones bind the receptor near the RGD site to that serves as a recognition and binding motif for ECM proteins [41, 42]. Previous study has been demonstrated that lncRNA NEAT1 can modulate miR-491 levels to regulate transglutaminase 2 (TGM2) and promote the transcriptional activation of FN1 through nuclear factor kappa B (NFkb) p65 nuclear translocation and consequently, lead to the PTC invasion and metastasis . In addition, overexpression of FN1 is also found in adioactivity iodine (RAI)- resistant PTC tissues where lncRNA-NEAT1/miR-101-3p/FN1 axis and PI3K/AKT signaling pathway are involved . Importantly, downregulation of NEAT1 can reverse the RAI resistance of PTC . For GALE, its mRNA expression was also found being increased in PTC tissues, but its role in PTC remains to be explored . Additionally, we have validated serum FN1 and GSN to differentiate patients with benign nodules and PTC by Elisa tests. The best ELISA result was from FN1 (sensitivity = 96.89%; specificity = 91.67%). Thus, we believe that additional studies are warranted to validate the serum levels of FN1, GSN and GALE as potential biomarkers for PTC in independent datasets from a large perspective clinical study.
In this study, we also demonstrate dysregulation of complement activation and coagulation cascades at the circulation level which are critical factors for cancer initiation or progression. The human complement system consists of about 50 serum proteins and membrane-bound regulators and receptors . It has been widely demonstrated that imbalanced complement activation contribute to regulating the functions and tumor-suppressing immune responses . Therapeutic targeting of complement system is also discussed .
In summary, the work presented here identifies a resource comprising proteomic regulations in the PTC tumor and circulation, highlights that integrin-mediated pathways, as well as complement activation and coagulation cascades, are regulated, and distinguishes FN1, GSN and GALE as promising biomarkers to achieve the diagnostics for those indeterminate cases. Notably, as discussed above, thyroid hormones can also regulate thyroid cancer cell proliferation through molecular and signaling pathways. The therapeutic targeting impinging on these signaling pathways thus best be explored. For example, the T4 analogue, tetraiodothyroacetic acid (tetrac) can block the actions of T4- integrin αvβ3 in thyroid cancer . Besides, T3 signaling through thyroid hormone receptor beta (TRβ) in the nucleus has a tumor-suppressive effect . In addition, thyroid hormone levels are regulated by the thyroid stimulating hormone (TSH) released from the pituitary. Sulaieva et al. show that TSH levels are not associated with PTC aggressiveness including LNM, TNM stage, and BRAFV600E mutation . Given by the complex of thyroid hormone regulation, future studies should also address their ability in relation to thyroid cancer.