Establishment and characterization of a new cell line from a hereditary renal rat tumor

Endoplasmic reticulum stress and cell death in mTORC1-overactive cells is induced by nelfinavir and enhanced by chloroquine

Inappropriate activation of mammalian/mechanistic target of rapamycin complex 1 (mTORC1) is common in cancer and has many cellular consequences including elevated endoplasmic reticulum (ER) stress. Cells employ autophagy as a critical compensatory survival mechanism during ER stress. This study utilised drug-induced ER stress through nelfinavir in order to examine ER stress tolerance in cell lines with hyper-active mTORC1 signalling. Our initial findings in wild type cells showed nelfinavir inhibited mTORC1 signalling and upregulated autophagy, as determined by decreased rpS6 and S6K1 phosphorylation, and SQTSM1 protein expression, respectively. Contrastingly, cells with hyper-active mTORC1 displayed basally elevated levels of ER stress which was greatly exaggerated following nelfinavir treatment, seen through increased CHOP mRNA and XBP1 splicing. To further enhance the effects of nelfinavir, we introduced chloroquine as an autophagy inhibitor. Combination of nelfinavir and chloroquine significantly increased ER stress and caused selective cell death in multiple cell line models with hyper-active mTORC1, whilst control cells with normalised mTORC1 signalling tolerated treatment. By comparing chloroquine to other autophagy inhibitors, we uncovered that selective toxicity invoked by chloroquine was independent of autophagy inhibition yet entrapment of chloroquine to acidified lysosomal/endosomal compartments was necessary for cytotoxicity. Our research demonstrates that combination of nelfinavir and chloroquine has therapeutic potential for treatment of mTORC1-driven tumours.

Effects of epidermal growth factor, fibroblast growth factor, retinoic acid and serum on anchorage-dependent and anchorage-independent growth of HRRT cells

The effects of EGF, FGF, RA and serum on anchorage-dependent and anchorage-independent growth of HRRT cells were studied. The five different types of serum tested in the present work induced a dose dependent rise in anchorage-independent growth in aggregates. FCS, SBCS and RS also supported colony formation in soft agar, whereas BS and HS had no significant effect. EGF and FGF stimulated anchorage-dependent growth of HRRT cells in monolayers. The peptide growth factors were also found to induce phenotypic transformation of the nonneoplastic HRRT cells, as measured by anchorage-independent growth in soft agar as well as in aggregates. At equimolar concentrations EGF was much more effective than FGF. The stimulating effect of EGF and FGF on cell proliferation in the aggregate form was markedly inhibited by RA. Treatment of HRRT cells with the highest noncytotoxic concentration of RA, 2 x 10(-7) M, reduced the stimulating effect of both growth factors by about 60%.

Initiation of in vitro cell transformation by formaldehyde and acetaldehyde as measured by attachment-independent survival of cells in aggregates

The ability of formaldehyde and acetaldehyde to initiate transformation of a rat kidney cell line has been studied using a newly developed two-stage in vitro cell transformation assay. The assay is based on measurements of attachment-independent survival of cells in aggregates. Short treatment with non-cytotoxic doses of formaldehyde and acetaldehyde did not affect survival of the cells in the aggregate assay system. However, when the aldehyde treatment was followed by exposure of the cells to the tumor promoters TPA and PDD, a considerable increase in the number of viable cells was observed. On a molar basis, formaldehyde was about 100 times more potent than acetaldehyde in initiation of cell transformation. The data showed that cells derived from aggregates of cultures treated with formaldehyde or acetaldehyde followed by exposure to TPA possessed a considerably higher ability to form colonies in soft agar than untreated control cells.