This is therefore suited for the study of de novo TJ formation and epithelial morphogenesis. Significant progress in the development of new therapies that can increase overall survival rates for a range of cancer types has been made. However, the heterogeneity within individual tumors and between tumors of the same type in different patients, as well as the different stages and sub-types of tumors, combine to confer a level of resistance to existing treatments in patients, and problems with the application of universal treatment strategies. Although chemotherapy remains one of the primary approaches for EGC treating cancer, conventional therapy is not specifically targeted to tumor cells and is therefore associated with a high level of side-effects, some of which can be severe. The development of drug resistance and other issues associated with biodistribution and drug clearance also pose significant problems and challenges. The difficulties in effectively targeting tumors that result from genetic and phenotypic heterogeneity have prompted the need for more specifically targeted approaches – ‘patient stratification’ and ECG ‘patient-focused medicine’. However, the ability to better treat a patient on the basis of the characteristics of their own tumor requires the identification of key target molecules or features. Although the ability to better identify tumor-associated antigens has led to the development of engineered human monoclonal antibodies for targeting a wide range of common malignancies and the use of radiolabeled antibodies as therapeutics for different kinds of hematological malignancies and solid tumors, the production and purification of therapeutic antibodies is timeconsuming and cost-intensive. Furthermore, antibodies derived from mice are not suitable for therapeutic approaches due to their immunogenicity in humans, and the affinity, avidity, or even the specificity of chimeric humanized antibodies often differ from those of the original murine antibody from which they are derived. The primary advantage of antibodies is their specificity and ability to target single molecules bearing the epitope. However, this can also be a disadvantage, as antibodies can only target those cancers which express the antigenic determinant.