A preliminary study of protoporphyrin-IX as a potential candidate for identification of lung cancer cells using fluorescence microscopy

Abstract

There is need for a cheap, sensitive, and specific method to identify and localize early stage lung cancer. In order to improve the sensitivity of fluorescent agents that exhibit selective tumor uptake that are used as population screening tools for the detection of early lung cancer, a number of porphyrins including protoporphyrin-IX (PpIX) were tested. We stained lung cancer cells using three different sample preparation schemes for fluorescence microscopy. Lung tissues and sputum samples of nineteen patients were studied. Cells were collected on glass slides by touching tumor surfaces of surgically sectioned lung cancer tissue and normal regions of the lung during surgery. Filtered sputum cells were also collected. Cell-attached slides were stained with porphyrin using three different methods, including fixing (SM-1) prior to staining, and diluting porphyrin stock solutions in either RPMI-1640 medium (SM-2) or 100mM MES buffer (SM-3). Slides from normal lung tissue lacked fluorescent epithelial cells. Tumor slides containing typical lung cancer cells exhibited red fluorescence upon excitation through the soret band (400-450 nm) of porphyrin compounds. Tumor-selective staining was only observed on unfixed tumor slides that were incubated with PpIX in a RPMI-1640 culture medium (SM-3) used as a working solution for staining and washing. Protoporphyrin-IX is a potentially useful tumor-staining molecular agent for fluorescent location of cancer cell in sputum samples from lung cancer patients.