Novel imaging technology and tools for biomarker detection in cancer

Abstract

Cancer is a leading cause of death worldwide. Normally the balance between cell growth and cell death is strongly controlled. Chronic lymphocytic leukemia is an indolent disease that has a highly variable clinical course and is the most common hematological malignancy amongst adults in the Western countries. The protein tyrosine phosphatase SHP-1 is a key regulator that controls the intracellular phosphotyrosine level in lymphocytes by inhibiting the B cell receptor signals. We have compared the expression and activity of SHP-1 in chronic lymphocytic leukemia cells from lymph nodes with matched peripheral blood samples. The expression levels of SHP-1 were higher in peripheral blood, but the phosphatase activity in lymph nodes and peripheral blood did not differ significantly. All cells in the body normally present glycans on the cell surface, which are involved in cellular communication and in processes like cell differentiation, proliferation and infection, including protecting the cells from invaders and in cell-cell contacts. Sialic acid occurs on the terminal end of glycans, and the frequency of sialic acid expression is increased on metastatic cancer cells and overexpression controls tumor cell growth and cell differentiation. The availability of specific antibodies against sialic acid is limited. We have been screening sialic acid on cancer cells by using a molecular imprinting polymer technique. Our results show that sialic acid is expressed on chronic lymphocytic leukemia cell lines at different levels at the plasma membrane. Higher expression of sialic acid in the more aggressive chronic lymphocytic leukemia cell lines was observed. To analyze morphological changes of death cells, digital holographic microscopy was used. Digital holographic microscopy is an approach for label-free non-invasive 3D imaging of cultured cells. We have analyzed cell death of adherent cancer cells using digital holographic microscopy and developed it to analyze suspension cells by combining this technique with antibody based microassays. Digital holographic microscopy can be used for cell-death induced cell analysis of both adherent cells and suspension cells. This thesis takes us one step further in cancer research as regards developing techniques for screening circulating cancer cells in blood as well as for individualized treatment of cancer patients