The Analysis Of The Relationship Between Stem Cell Marker CD90and Cisplatin Resistance Of Lung Cancer

Background：Lung cancer, which has been high morbidity and mortality, is one of the most commonmalignant tumors in today’s society. The5-year survival rate is about15%. Thechemotherapy drug resistance is one of the reasons for the low survival rate of patients withlung cancer. Explore the causes of chem-resistance and find new treatment approach toreverse the chemo-resistance will improve lung cancer efficacy, and benefit many patientswith lung cancer.Cancer stem cells (CSCs) theory provides a new insight into tumorigenesis mechanism,and also provides a new perspective to conquer chemo-resistance of cancer. CSCs arethought to be a small proportion existing in the tumor cells. They are a subpopulation cellswith stem cell characteristics such as unlimited self-renewal and multi-directionaldifferentiation potential.Thus, they have the ability to induce tumorigenesis. A lot of studieshave demonstrated that CSCs played an important role in the occurrence, metastasis,invasion and recurrence of variety tumors.Existing studies have shown that chemotherapy drug resistance, along with ability ofself-renewal and multi-directional differentiation potential, is the important characteristicsof cancer stem cells. What’s more, the chemotherapy drug resistance of cancer stem cells isan important reason for recurrence of the tumor after chemotherapy. Therefore, furtherstudy about the relationship between cancer stem cells and the chemotherapy drugresistance will certainly be beneficial to reverse chemotherapy drug resistance.So far, the isolation of CSCs was mainly performed by the use of surface molecularmarkers and side population cells. At present, a large number of studies suggested thatCD90was an ideal molecular surface marker of liver cancer stem cell, but it was stillunknown that whether CD90could be molecular surface marker of lung cancer stem cell.In the previous study, our group cultured tumor cell spheres in serum-free conditioned medium to identify the lung cancer stem-like cells, and further study had identified thecharacteristics of stem cells in tumor spheres. Compared with lung adenocarcinoma cancercell A549adhere cells, A549sphere cells expressed higher level of stem cell marker CD90.By colony formation assay, spheres formation assay and xenografts, We found that CD90+A549cells showed higher ability of self-renewal and tumorigenicity in nude mice thanCD90-A549cells. It indicated that CD90might be a marker of lung cancer stem cells. So,our study tries to research the relationship between CD90and cisplatin resistance of lungcancer. This may provide futher evidence for whether CD90is molecular marker of lungcancer stem cells.Objective：To research the relationship between CD90and cisplatin resistance in A549cells，so asto identify whether CD90is molecular marker of lung cancer stem cells from the view ofdrug resistance.Methods：1. Spheres formation assay, CCK-8assay, colony formation assay were used toobserve the ability of spheres formation, cell proliferation and colony formation in A549and A549/CDDP cells. To detect the relationship between stem cell characteristics andchemotherapy resistance of lung cancer cells;2. On the basis of above research, FCM was performed to compare the expression levelof stem cell marker CD90;3. The CD90+and CD90-A549were separated by FCM. The cell toxicity test andtumorigenicity in nude mice were performed to compare the cisplatin resistance betweentwo kinds of cells both in vivo and in vitro.Results：1. Compared with A549cell, the A549/CDDP had significantly enhanced ability ofspheres formation, cell proliferation and colony formation (p <0.05);2. Both in adherent cells and sphere cells, A549/CDDP contained higher level ofCD90positive cells than parental A549cell line (p <0.05);3. The result of cell toxicity test in vitro and tumorigenicity in nude mice in vivoshowed that CD90+A549cell group is more resistant to cisplatin (p <0.05).Conclusion： A549/CDDP cell had a higher self-renewal ability and higher proportion of CD90positive cells than A549cell. CD90+A549cell was more resistant to cisplatin than CD90-A549cell. As a result, our research indicated that CD90might be a marker of lung cancerstem cells from the respect of chemotherapy resistance.