The research outlined in this thesis aims to further our knowledge of the biological characteristics underlying the aggressive behaviour by which pancreatic cancer invades and metastasises at an early stage and is refractory to most chemotherapeutic drugs. Investigation into drug resistance in pancreatic cancer involved pulse-selection of three cell lines with epirubicin, taxotere and gemcitabine. The drug-selected cell lines, in general, displayed low changes in sensitivity to their respective selecting drugs and no obvious cross-resistance profile. However, drug treatment modulated the invasive potential of the pulse-selected cell lines. Expression of multi-drug resistant proteins (P-gp and MRP-1) was also determined by IHC in 45 pancreatic tumour specimens, results suggested a contributory role for P-gp expression in pancreatic cancer. An in vitro pancreatic invasion model was established by single cell cloning of MiaPaCa-2, yielding sub-clones displaying diverse invasive properties. The malignant phenotypes of MiaPaCa-2, Clone #3 (highly invasive) and Clone #8 (poorly invasive) were characterised, comparative proteomic profiling by 2-D DIGE, MALDI-TOF MS and RNAi revealed three targets, ALDH1A1, VIM and STIP1 with functional involvement in the invasion process. ALDH1A1 appeared to play a role in the aggressive invasive phenotype; expression was associated with increased invasion, drug resistance and decreased adhesion. VIM and STIP expression was also linked to increased invasion and decreased adhesion, with STIP1 displaying a role in proliferation, which has not previously been described. Factors secreted into conditioned media of Clone #3 and Clone #8 was also examined by proteomics. Targets, GSN and ALDH1A1 were chosen for functional analysis and their potential involvement in cancer cell invasion assessed. EGFR/HER2 expression was analysed in 5 pancreatic cancer cell lines, and two cell lines which co-expressed EGFR and HER2 were tested with lapatinib. Lapatinib, a dual EGFR/HER2 inhibitor in combination with chemotherapeutic drugs showed additive interactions, suggesting the possibility of a therapeutic role for lapatinib in combination with chemotherapy in pancreatic cancer patients co-expressing EGFR/HER2.