Provided are engineered B lymphocytes modified to express one or several different types of microRNAs or anti-miRs where in one embodiments the lymphocytes contain multiple copy numbers of nucleic acids encoding the one or several different types of miRs or anti-miRs. Provided are compositions and methods for treating, ameliorating, or preventing a cancer cell, a breast cancer cell or a triple negative breast cancer, or a breast cancer cell that tests negative for estrogen receptors, progesterone receptors, or HER2, comprising or by administering a composition, formulation or pharmaceutical composition comprising a microRNA or anti-miR. Provided are methods for treating an inflammation, a disease, a condition, infection or cancer capable of being treated by modulation or inhibition or expression of an miRNA or anti-miRs by administering to an individual in need thereof a B lymphocyte that secretes a microRNA or anti-miR, or a B lymphocyte supernatant, extracellular vesicle or exosome having a microRNA or anti-miR.