Distribution of Photofrin between tumour cells and tumour associated macrophages

Abstract

Photofrin levels in cells derived from SCCVII tumours, excised from mice that previously received the drug, were measured using a fluorescence activated cell sorter (FACS). Concomitantly, in the same cells the FACS was used to measure fluorescein isothiocyanate (FITC) fluorescence that originated from FITC-conjugated antimouse IgG added to the cell suspension before sorting. This later measurement enabled discrimination between IgG negative tumour malignant cells and IgG positive host cells (primarily macrophages). In addition, cellular Photofrin content in 'tumour' and 'host' cells sorted by FACS was determined by chemical extraction. The measurements were performed for the time intervals 1-96 h post Photofrin administration. The data showed consistently higher Photofrin levels in the 'host cells', i.e., tumour associated macrophages (TAM), than in 'tumour' cells. On a per cell basis, at any time point studied there was a minimum of 1.7 times more Photofrin in 'host' than in 'tumour cells', while at 4-12 h postadministration, ratios of up to 3.0 times were observed. This corresponds to ratio values greater than 9, when based on Photofrin content per micrograms cell protein.

Photofrin accumulation in malignant and host cell populations of various tumours

“…Since monoclonal antibodies to the hamster cell membrane antigens (equivalent to those employed in the mouse experiments) were not available to us, the FITCconjugated anti-hamster IgG was used to stain the tumour cell suspensions. This staining separates TAMs (which are FcR positive) from the malignant cell population (FcRcells), as shown previously in mouse tumour models (Korbelik et al, 1991).…”

“…In our first report, we showed (using the mouse SCCVII tumour model) that the population of cells characterised by the presence of the Fc receptor accumulates higher Photofrin levels than the malignant cell population, which is FcR negative (Korbelik et al, 1991). The FcR-positive cell population in this tumour consists predominantly of tumour-associated macrophages (TAMs).…”

Increasing the effect of photodynamic therapy on the RIF-1 murine sarcoma, using the bioreductive drugs RSU1069 and RB6145

“…The following main conclusions can be drawn from the results of this study: including macrophages, can differ in their rates of uptake and in their retention of photosensitisers (Chan et al, 1988;Henderson & Bellnier, 1989;Korbelik et al, 1991). This may be of importance for the overall tumour response to PDT for a particular tumour type.…”

Cellular levels of photosensitisers in tumours: the role of proximity to the blood supply

“…The insert to Figure 6 shows the representative examples for a 'large' tumour (241 mg wet weight) and a 'small' tumour (19 mg wet weight). (Korbelik et al, 1991;Korbelik, 1993), it was important to examine the photosensitiser diffusion profiles separately in these two different tumour cell populations. Using a technique described previously (Korbelik, 1993), the FsaR tumour cell suspension was separated into the Fc receptor-positive cells (predominantly TAMs) and the cells stained negatively for the Fc receptor (predominantly malignant cells) (Figure 7).…”

“…Macrophages are the most prominent population of host cell infiltrate in many tumours. These cells retain markedly higher levels of Photofrin and other photosensitisers than the parenchymal malignant cells (Korbelik et al, 1991: Korbelik. 1993: Korbelik & Krosl. 1993).…”