No abstract

Tumor necrosis factor (TNF) is a polypeptide cytokine that is cytotoxic to some but not all tumor cells. The basis for resistance to the cytotoxic effects of this agent remains unclear. We have studied the development of TNF resistance in human ZR-75-1 breast carcinoma cells. ZR-75-1 cells have undetectable levels of TNF RNA and protein. However, TNF transcripts are transiently induced in these cells by exposure to recombinant human TNF. This induction of TNF RNA is associated with production of TNF-like protein in cell lysates and culture supernatants. Stable resistance to TNF-induced cytotoxicity develops when ZR-75-1 cells are exposed to increased concentrations of TNF. The TNF-resistant cells, designated ZR-75-1R, continuously express TNF transcripts and a TNF-like protein. Furthermore, ZR-75-1R cell supernatants contain cytotoxic activity that is abrogated by polyclonal antibody against TNF. The ZR-75-1R cells also possess TNF receptors that are occupied or down-regulated by the TNF-like protein. These findings thus suggest that (') TNF induces TNF transcripts and production of a TNF-like protein in ZR-75-1 cells and (it) resistance to TNF-induced cytotoxicity is associated with stable TNF expression.Tumor necrosis factor (TNF) is a polypeptide cytokine that exerts a wide variety of biological effects (1). TNF was originally identified by its ability to cause hemorrhagic necrosis in subcutaneous murine tumors (2). Subsequent studies showed that TNF is cytotoxic to certain murine and human tumors, both in vitro and in vivo (1-3).The cytotoxic effects of TNF appear to be cell cycledependent. TNF causes accumulation ofcells in G2 phase and cytolysis in late stages of mitosis (4). This cytolytic effect is enhanced by inhibitors of RNA and protein synthesis (5, 6). Tumor cells sensitive and resistant to TNF-induced cytotoxicity have similar numbers of cell surface receptors. Furthermore, both sensitive and resistant cells internalize and degrade TNF after receptor binding (7). Thus, cell surface receptors appear to be necessary but not sufficient for TNF cytotoxicity (8)(9)(10). The basis for the sensitivity or resistance of transformed cells to TNF remains unknown.Exposure of TNF-sensitive L-929 mouse fibroblasts to TNF results in the development of stable TNF resistance (11). Paradoxically, this TNF-resistant subline produces a TNF-like protein that is cytotoxic to the parent L929 cell line. We recently demonstrated that certain human epithelial tumor cell lines inherently resistant to TNF also produce both TNF mRNA and protein (unpublished work). These findings suggested that production of TNF may be associated with TNF resistance. The present studies investigated this relationship in human breast carcinoma cells sensitive to the cytotoxic effects of TNF in vitro. The results show that TNF treatment induces both TNF expression and resistance to TNF cytotoxicity. METHODSCell Culture. The ZR-75-1 human breast carcinoma cells were obtained from the American Type Culture Collection and grown in RPMI 1640 ...

Efficient in silico development of novel antibiotics requires high-resolution, dynamic models of drug targets. As conjugation is considered the prominent contributor to the spread of antibiotic resistance genes, targeted drug design to disrupt vital components of conjugative systems has been proposed to lessen the proliferation of bacterial antibiotic resistance. Advancements in structural imaging techniques of large macromolecular complexes has accelerated the discovery of novel protein-protein interactions in bacterial type IV secretion systems (T4SS). The known structural information regarding the F-like T4SS components and complexes has been summarized in the following review, revealing a complex network of protein-protein interactions involving domains with varying degrees of disorder. Structural predictions were performed to provide insight on the dynamicity of proteins within the F plasmid conjugative system that lack structural information.

Tumor necrosis factor (TNF) is a monokine with in vitro cytotoxicity for some but not all tumor cells. The basis for sensitivity and resistance to the antitumor effects of this agent remains unclear. The present studies have monitored the effects ofTNF on 14 epithelial tumor cell lines. Eleven of these cell lines were resistant to the growth inhibitory effects of TNF (50% inhibitory concentration > 1,000 U/ml). 12 of the 14 tumor cell lines has detectable levels of high affinity cell surface TNF binding sites, thus suggesting that resistance was not often due to the absence of cell surface TNF receptors. Northern blot analysis demonstrated that three of the eleven resistant cell lines expressed detectable levels of TNF mRNA. Furthermore, both sensitive and resistant epithelial tumor cells had the capacity to express TNF transcripts in the presence of the protein synthesis inhibitor, cycloheximide. Finally, the presence of TNF expression at the RNA level is shown to be associated with the production of a TNF-like protein in the resistant Ov-D ovarian carcinoma cells. These findings suggest that certain human epithelial tumor cell lines inherently resistant to TNF also express this cytokine.

Background Mismatch repair proficient (MMRp) colorectal cancer (CRC) has been refractory to single‐agent programmed cell death protein 1 (PD1) inhibitor therapy. Colon GVAX is an allogeneic, whole‐cell, granulocyte‐macrophage colony‐stimulating factor ‐secreting cellular immunotherapy that induces T‐cell immunity against tumor‐associated antigens and has previously been studied in combination with low‐dose cyclophosphamide (Cy) to inhibit regulatory T cells. Methods We conducted a single‐arm study of GVAX/Cy in combination with the PD1 inhibitor pembrolizumab in patients with advanced MMRp CRC. Patients received pembrolizumab plus Cy on day 1, GVAX on day 2, of a 21‐day cycle. The primary endpoint was the objective response rate by Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1. Secondary objectives included safety, overall survival, progression‐free survival, changes in carcinoembryonic antigen (CEA) levels, and immune‐related correlates. Results Seventeen patients were enrolled. There were no objective responses, and the disease control rate was 18% by RECIST 1.1. The median progression‐free survival was 82 days (95% confidence interval [CI], 48‐97 days) and the median overall survival was 213 days (95% CI 179‐441 days). Biochemical responses (≥30% decline in CEA) were observed in 7/17 (41%) of patients. Grade ≥ 3 treatment‐related adverse events were observed in two patients (hemolytic anemia and corneal transplant rejection). Paired pre‐ and on‐treatment biopsy specimens showed increases in programmed death‐ligand 1 expression and tumor necrosis in a subset of patients. Conclusions GVAX/Cy plus pembrolizumab failed to meet its primary objective in MMRp CRC. Biochemical responses were observed in a subset of patients and have not previously been observed with pembrolizumab monotherapy in MMRp CRC, indicating that GVAX may modulate the antitumor immune response.