Cell‐type Selective Phototoxicity Achieved with Chlorophyll‐a Derived Photosensitizers in a Co‐culture System of Primary Human Tumor and Normal Lung Cells

Abstract

The ATP-dependent transporter ABCG2 exports certain photosensitizers (PS) from cells, implying that the enhanced expression of ABCG2 by cancer cells may confer resistance to photodynamic therapy (PDT) mediated by those PS. In 35 patient-derived primary cultures of lung epithelial and stromal cells, PS with different subcellular localization and affinity for ABCG2 displayed cell-type specific retention both independent and dependent on ABCG2. In the majority of cases, the ABCG2 substrate 2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-a (HPPH) was lost from fibroblastic cells more rapidly than from their epithelial counterparts, even in the absence of detectable ABCG2 expression, facilitating selective eradication by PDT of epithelial over fibroblastic cells in tumor/stroma co-cultures. Pairwise comparison of normal and transformed epithelial cells also identified tumor cells with elevated or reduced retention of HPPH, depending on ABCG2. Enhanced ABCG2 expression led to the selective PDT survival of tumor cells in tumor/stroma co-cultures. This survival pattern was reversible through HPPH derivatives that are not ABCG2 substrates or the ABCG2 inhibitor imatinib mesylate. PS retention, not differences in subcellular distribution or cell signaling responses, was determining cell type selective death by PDT. These data suggest that up-front knowledge of tumor characteristics, specifically ABCG2 status, could be helpful in individualized PDT treatment design.

Effect of chirality on cellular uptake, imaging and photodynamic therapy of photosensitizers derived from chlorophyll-a

“…Since uptake and subcellular distribution of pyropheophorbides are subject to cell type-specific difference 36 the isolated isomers, as well as the isomeric mixture, were tested in representative cultures of fibroblastic and epithelial cells. The initial survey determined in vitro uptake, intra-cellular localization and in vitro PDT efficacy in murine Colon26 cells (supporting material information: Fig.…”

“…Analyses of the compounds were carried out with two types of cells: Colon26 murine colon tumor cells as described previously and primary cultures of fibroblasts and epithelial cells from human lung tumor tissue 36 . Surgical lung specimens were provided by RPCI tissue procurement service and were processed to recover monotypic cultures of epithelial and stromal fibroblast following published procedures 36 .…”

“…Surgical lung specimens were provided by RPCI tissue procurement service and were processed to recover monotypic cultures of epithelial and stromal fibroblast following published procedures 36 . Proliferating epithelial cells (all labeled by the number of lung tumor sample registered in the laboratory records, e.g., “L370-T-EC”) were maintained on collagen-1-matix in keratinocyte serum-free medium (KSFM) supplemented with growth factor and cholera toxin (Live Technologies).…”

“…The treatments of various cell types in tissue cultures with 3-[1’-( m -iodobenzyloxyethyl)-3-devinylpyropheophorbide-a and structural analogs 36 have indicated that side groups added to the porphyrin ring affect the mode of cellular uptake and intracellular distribution. Not yet known is the impact of stereoisomerism on the cell biology of the compounds.…”

Photodynamic therapy of cancer — Challenges of multidrug resistance

“…Tracy et al demonstrated in tumor/stroma cocultures derived from lung cancers that HPPH was lost from¯broblastic cells more rapidly than from epithelial cells, even under low BCRP expression, facilitating selective eradication by PDT of epithelial over¯broblastic cells. 51 Enhanced BCRP expression led to the selective PDT survival of tumor cells in tumor/stroma co-cultures. This survival pattern was reversible through no-substrate HPPH derivatives or imatinib mesylate.…”