A complete understanding of the biological mechanisms regulating devastating disease such as cancer remains
elusive. Pancreatic and brain cancers are primary among the cancer types with poor prognosis. Molecular biomarkers
have emerged as group of proteins that are preferentially overexpressed in cancers and with a key role in driving disease
progression and resistance to chemotherapy. The epidermal growth factor receptor (EGFR), a cell proliferative
biomarker is particularly highly expressed in most cancers including brain and pancreatic cancers. The ability of EGFR
to sustain prolong cell proliferation is augmented by biomarkers such as Bax, Bcl-XL and Bcl-2, proteins regulating the
apoptotic process. To better understand the role and effect of the microenvironment on these biomarkers in pancreatic
cancer (PaCa); we analysed two pancreatic tumor lines (AsPc-1 and MiaPaCa-2) in 2D, 3D in-vitro cultures and in
orthotopic tumors at different growth stages. We also investigated in patient derived glioblastoma (GBM) tumor cultures,
the ability to utilize the EGFR expression to specifically deliver photosensitizer to the cells for photodynamic therapy.
Overall, our results suggest that (1) microenvironment changes affect biomarker expression; thereby it is critical to
understand these effects prior to designing combination therapies and (2) EGFR expression in tumor cells indeed could
serve as a reliable and a robust biomarker that could be used to design targeted and image-guided photodynamic therapy.