Tumors induce de novo steroid biosynthesis in T cells to evade immunity

Tumors subvert immune cell function to evade immune responses, yet the complex mechanisms driving immune evasion remain poorly understood. Here we show that tumors induce de novo steroidogenesis in T lymphocytes to evade anti-tumor immunity. Using a transgenic steroidogenesis-reporter mouse line we identify and characterize de novo steroidogenic immune cells, defining the global gene expression identity of these steroid-producing immune cells and gene regulatory networks by using single-cell transcriptomics. Genetic ablation of T cell steroidogenesis restricts primary tumor growth and metastatic dissemination in mouse models. Steroidogenic T cells dysregulate anti-tumor immunity, and inhibition of the steroidogenesis pathway is sufficient to restore anti-tumor immunity. This study demonstrates T cell de novo steroidogenesis as a mechanism of anti-tumor immunosuppression and a potential druggable target.

Separation of leukemic cells into proliferative and quiescent subpopulations by centrifugal elutriation

Centrifugal elutriation was used to separate human acute leukemia cells into proliferative and quiescent subpopulations. Ten bone marrow specimens and 5 peripheral blood specimens were subjected to centrifugal elutriations. From each patient, leukemic cell subpopulations were obtained for which the [3H]thymidine labeling index differed by 10- to 30-fold. In 6 of the marrow specimens and in 2 of the peripheral blood specimens, cell subpopulations were obtained for which the labeling index exceeded 20%. In 5 marrow specimens, subpopulations were obtained for which the labeling index exceeded 40%. Preliminary studies of the uptake of 1-beta-D-arabinofuranosylcytosine and 5-azacytidine failed to show any correlation between drug uptake and the proliferative characteristics of the leukemic subpopulations.

Drug uptake and ribonucleotide profiles of blast-enriched and blast-depleted human bone marrow cell populations

A density cut method was used to prepare two subpopulations of bone marrow cells which were enriched (BE) and depleted (BD) respectively of blast cells. Marrow aspirates were obtained from 32 patients, 26 of whom had acute leukaemia. The uptake of a variety of chemotherapeutic agents by these two subpopulations and the acid-soluble ribonucleotide profiles of the populations were compared and significant differences were found in drug uptake by BE and BD subpopulations. For some drugs such as cytosine arabinoside, uptake was greatest by the BE cells, while for 5-azacytidine the BD subpopulation took up the greatest amount of the drug. The preparation of the BE subpopulation also permitted the recognition of several patients with acute leukaemia whose blast cells possess nondetectable levels of ATP, UTP, and GTP components in their acid-soluble fractions. The studies presented demonstrate the necessity of using purified cell populations when characterizing the drug uptake patterns and the soluble ribonucleotide profiles of the leukaemic cells. A simple method for enriching bone marrow aspirates for leukaemic cells is also presented.