Cancer Metastasis Dynamics:the Mechanism Of Cancer Cells With Stillness To Activation And Metastasis

Cancer is a serious public health problem in the world.Metastasis is the principal cause of cancer-associated death and a major challenge in today’s cancer management.Metastasis and death is the daily threat to the cancer survivors,and the number of cancer survivors continues to grow in the world.Although many new diagnostic techniques and therapies against malignant tumors have been developed over the last years,the prognosis of most cancer survivors remains unfavorable.A primary reason is that current therapies directed against metastasis are too late because cancer cells have already seeded to various vulnerable tissues.Therefore,it is very important to explore a new avenue,as namely "cancer metastatic chemoprevention",to develop specific therapies to prevent cancer metastasis.Based on the above consideration,and combined with the previous research foundation,we constructed a new theory of cancer metastasis dynamics.In this doctoral thesis,we explored that circulating tumor cells(CTCs)and cancer microenvironment(including cytokines,platelets and TGF-β,et al.)relationship with cancer metastasis,and unraveled the key mechanisms of cancer metastasis which could provide a rationale for the research of cancer metastasis alert and prevention.In addition,based on novel cancer metastasis dynamics theory and cancer metastatic chemoprevention strategy,S-nitrosocaptopril(CapNO)which shows a good safety profile,could serve as a unique metastatic chemopreventive.The detailed research contents and achievements are summarized as follows:1.Cancer metastasis dynamics research based on circulating tumor cells(CTCs)In chapter 2,we have established and validated a method of immunomagnetic negative enrichment coupled with fluorescence-activated cell sorting(FACS)for the detection,isolation,and characterization of CTCs from the blood of cancer patients.The number of CTCs and percentage of CD44+ CTCs are well correlated with colorectal patient TNM stages.These results suggest that the CTCs might help us to predict patient’s situation and potentially to select the therapeutic strategy properly.In chapter 3,we tracked the number of CTCs in the blood circulation system of mouse dynamically,and established the CTCs kinetic equation of circulation which is the relationship between quantity and time.Reference to the pharmacokinetic study Imodel,we found that CTCs can specifically bind to tissues and organs.Syngeneic mouse experimental metastatic models demonstrated that many types of tumor metastasis are organ-specific,and mouse organs imaging observation demonstrated that CTCs distribute in specific organs.These results indicate that organ-specific metastasis is closely related to the blood circulation patterns.2.Cancer metastasis dynamics research based on cancer microenvironmentIn chapter 4 and 5,fluorescence-based analysis showed that inflammation cytokines and activated-platelets promote hetero-adhesion of cancer cells to endothelial cells.Further mechanism research demonstrated that inflammation cytokines induce the expression of cell adhesion molecules(CAMs,including ICAM-1,VCAM-1 and E-selectin)on endothelial cells by invoking NF-κB signal pathway.The activation of expression of CAMs caused by cytokines is concentration-and time-dependent,and the combination of cytokines can arouse strong synergistic effects to induce CAMs expression.Activated-platelets were significant increase platelet-cloaked tumor cell aggregates.Further study showed that the mechanism of early tumor cell-platelet interactions could be mediated by P-selectin binded to tumor cell surface ligand Sialyl Lewisx(Slex).What’s more,tumor cell-platelet interactions can promote the secretion of TGF-β and then activate pSmad expression.In chapter 6,TGF-β can enhance the metastasis activity of HCT116 cells via inducing epithelial-mesenchymal transition(EMT),reprograming metabolism and upregulating glycolysis.TGF-P-induced highly metastatic HCT116(T-HCT116)cells easily adapt to oxidative phosphorylation(OXPHOS)suppression by sustained elevation in glycolysis and regulation of cell proliferation and invasion.These results suggest that the T-HCT116 cells can use the limited energy more effectively in order to adapt to the cancer microenvironment.In chapter 7,the SW480 cell line was derived from a primary colorectal cancer,whereas the SW620 cell line was derived from a lymph node metastasis of the same patient.Bioenergetic adaptation of metastatic SW620 cells can reduce unrequired bioenergy consuption in emergencies,which was consistent with the T-HCT116 cells.In comparison to SW480 cells,SW620 has a better micerenvironment adaptability.In chapter 8,investigating the expression of cancer cells surface protein,we found that CD44,CD133 and CD166 are associated with cancer metastatic activity.3.CapNO prevents cancer metastasis research based on cancer metastasis dynamics theoryIn chapter 9 and 10,CapNO makes direct vasorelaxation and increases blood flow,could make the diameter of capillaries larger to prevent CTCs from being trapped.CapNO interferes with the hetero-adhesion between CTCs and vascular endothelial cells by down-regulation of CAMs expression which induced by cytokines invoking NF-kB signal pathway.CapNO inhibits platelet activation and CTC-platelet interaction by decreasing the expression of P-selectin on platelets and Slex on cancer cells.Furthermore,CapNO also have antithrombotic capacity,and inhibits cancer cells glycolysis by downregulating HK1/HK2 expression.Syngeneic mouse experimental metastatic models further demonstrated that CapNO has a remarkable inhibitory effect on cancer metastasis.This new discovery provides a basis for CapNO being used for cancer metastatic chemoprevention.In summary,we constructed a new theory of cancer metastasis dynamics,and initially studied the impact of cancer microenvironment to progress of cancer metastasis.CTCs arrest in specific organs according to the blood circulation patterns.Then the CTCs bond to endothelial cells by receptor/ligand interplay when stimulated by cytokines.CTCs-platelets interaction secrete TGF-β which could induce CTCs to go through EMT.After that,the cancer cells reprogram metabolism and upregulate glycolysis,which would be beneficial for cancer cells to adapt to new tumor microenviroment and form micrometastases timely.The theory of cancer metastasis dynamics provide a significant theoretical,basis for cancer metastasis prevention drugs research.The potential cancer metastatic prevention effect of CapNO indicates the profound significance of this theory which establish a new avenue for cancer metastatic prevention.