M.Sc Thesis

M.Sc StudentKortam Sally
SubjectMechanobiology of Cancer for Clinical
Assessment of Cell Invasiveness
DepartmentDepartment of Biomedical Engineering
Supervisor ASSOCIATE PROF. Daphne Weihs


Background: Non-melanoma skin cancers, including basal cell carcinomas (BCCs) and squamous cell carcinomas (SCCs), are the most common malignancies worldwide with prevalence rising annually. BCC/SCC skin cancers are generally highly localized and can be surgically excised, however, invasive tumors may be fatal. Diagnosis of skin cancer and prognosis of potential invasiveness is based mainly on clinical-pathologic factors of the biopsied lesions. For SCC or melanoma, invasiveness is also predicted by histo-morphological factors, respectively, the degree of differentiation (e.g. well/moderate/poor) or the mitotic index. For skin BCC, however, invasiveness is only predicted by the clinical-pathologic factors and the tumor type (e.g. sclerosing, morphea). The above subjective measures do not provide direct, objective prognosis of cellular invasiveness. It is thus important to identify invasive fractions, their response to varying microenvironment, and to provide the predicted metastatic risk of a sample as rapidly as possible. Using the Weihs lab innovative mechanobiology-based approach, we can rapidly (2-hr) identify invasive cells and quantify the likelihood for invasiveness, while also evaluating effects of substrate stiffness.

Methods: Cells are enzymatically collected from fresh, suspected of non-melanoma skin tumors and seeded on physiological-stiffness synthetic gels and within 1-hr, mechanically invasive cell-subsets push/indent the gels. Quantification of the percentage of indenting cells and their attained depths, together providing the mechanical invasiveness, are used to determine likelihood for invasiveness. To evaluate effects of gel stiffness on the mechanical invasiveness we have also evaluated cell lines of primary-site and metastatic cancers on physiological-stiffness values of 0.8, 2.4 and 5 kPa.

Results: Invasive and non-invasive SCC samples differ significantly in the mechanical invasiveness, in agreement with the clinical histopathology and judgement. We demonstrate direct agreement between the differentiation state of cells in SCC samples and the rapid and quantitative mechanical invasiveness measure. In BCC samples, highly migratory, desmoplastic samples are also rapidly identifiable. Concurrently, we observe that while benign cells appear to be relatively insensitive to gel stiffness, their mechanical invasiveness of metastatic cells is influenced by the substrate stiffness; the response is nonuniform, yet is substrate stiffness and cancer type dependent.

Conclusions: We provide rapid (2-3hr), unbiased, accurate and quantitative measure of the likelihood for invasiveness in direct agreement with clinical histopathology. This technology can provide clear guidelines for rapid decision making (bed-side), on the time-scale of the initial diagnosis, where early prognosis of invasiveness risk will allow appropriate choice of treatments and disease-management protocols.