Tumors are considered to be possible targets of immunotherapy using stimulated and expanded autologous or allogeneic natural killer (NK) cells mismatched for MHC class I molecules and inhibitory NK receptors. NK cellbased immunoadjuvant therapies are carried out in combination with standard chemotherapeutic protocols. In the presented study, we characterized the effect of 28 frequently used chemotherapeutic agents on the capacity of NK cells to kill target cells. We found that treatment of NK cells with the drugs vinblastine, paclitaxel, docetaxel, cladribine, chlorambucil, bortezomib, and MG-132 effectively inhibited NK cell -mediated killing without affecting the viability of NK cells. On the other hand, the following drugs permitted efficient NK cell -mediated killing even at concentrations comparable with or higher than the maximally achieved therapeutic concentration in vivo in humans: asparaginase, bevacizumab, bleomycin, doxorubicin, epirubicin, etoposide, 5-fluorouracil, hydroxyurea, streptozocin, and 6-mercaptopurine. [Mol Cancer Ther 2007;6(2):644 -54]

Increasing evidence indicates that cancer development requires changes both in the precancerous cells and in their microenvironment. To study one aspect of the microenvironmental control, we departed from Michael Stoker's observation (Stroker et al, J Cell Sci 1966;1:297-310) that normal fibroblasts can inhibit the growth of admixed cancer cells (neighbour suppression). We have developed a high-throughput microscopy and image analysis system permitting the examination of live mixed cell cultures growing on 384-well plates, at the single cell level and over time. We have tested the effect of 107 samples of low passage number (<5) primary human fibroblasts from pediatric and adult donors, on the growth of six human tumor cell lines. Three of the lines were derived from prostate carcinomas, two from lung carcinomas and one was an EBVtransformed lymphoblastoid line. Labeled tumor cells were grown in the presence of unlabeled fibroblasts. The majority of the tested fibroblasts inhibited the proliferation of the tumor cells, compared to the control cultures where labeled tumor cells were co-cultured with unlabeled tumor cells. The proliferation inhibiting effect of the fibroblasts differed depending on their site of origin and the age of the donor. Inhibition required direct cell contact. Mouse 3T3 fibroblasts inhibited the growth of SV40-transformed 3T3 cells and human tumor cells, showing that the inhibitory effect could prevail across the species barrier. Our high-throughput system allows the quantitative analysis of the inhibitory effect of fibroblasts on the population level and the exploration of differences depending on the source of the normal cells.

Tumors are considered to be possible targets of immunotherapy using stimulated and expanded cytotoxic T-lymphocytes (CTL). It is important to consider the drug-induced effects when chemotherapeutic regimens and CTL-mediated immunotherapy is planned to be used in parallel. In this study, we characterized the effect of 29 frequently used chemotherapeutic agents on the cytotoxic activity of autologous and allogeneic CTLs. We found that treatment of CTLs with the following drugs: docetaxel, vincristine, chlorambucil, mitomycin C, oxaliplatin, doxorubicin, and bleomycin effectively inhibited CTL-mediated killing, without affecting their viability. On the other hand, the following drugs enhanced or permitted efficient CTL-mediated killing in vitro at concentrations comparable with the maximally achieved therapeutic concentration in vivo in humans: daunorubicin, prednisolone, vinorelbine, cisplatin, methotrexate, hydroxyurea, cytarabine, cyclophosphamide, topotecan, epirubicin, fluorouracil, carboplatin, asparaginase, 6-mercaptopurine, and bortezomib. Our results could potentially be used in the future to design new CTL-based adjuvant immunotherapy protocols.