A complete understanding of the molecular basis of cancers depends on novel molecular probes to recognize targets of interest. Currently, molecular medicine lacks sufficient molecular probes for the effective study of human diseases like cancer. A new class of designer nucleic acids (termed aptamers) holds great promise in meeting this challenge. Aptamers, which can be selected for single proteins and even small molecules, can be created by a strategy known as SELEX. Instead of using single type of molecules as a target for aptamer selection, we have developed a process, termed cell-SELEX, for aptamer selection using intact living cancer cells. By cell-SELEX, aptamers can be selected for the specific recognition of individual cell types without prior knowledge of the biomarkers for the cell. The selection process is simple, fast, and reproducible. The selected aptamers can bind to target cells with dissociation constants in the nanomolar to picomolar range.
So far, we have selected aptamers for nine different cancers (three different types of leukemia (T-cell, B-cell and AML), two types of lung cancers (small cell lung cancer and non-small cell lung cancer), liver cancer, colon cancer, ovarian cancer and breast cancer), infectious diseases and stem cells. All these aptamers worked well for the specific recognition of cancer cells. We used these aptamers in combination with molecular biology, bioanalysis, biophysics, biomedical engineering and nanotechnology in making a variety of advanced molecular tools for molecular medicine. These new tools based on aptamers could be used for early diagnosis and targeted therapy of cancer. Using the aptamers, we are also able to discover new biomarkers for specific cancers.