Breast cancer is the most common malignancy in women, accounting for 27% of all female cancers; it accounts for < 1% of all cancer cases in men. Breast cancer also is responsible for 15% of cancer deaths in women, making it the number-two cause of cancer death.Human umbilical cord-derived mesenchymal stem cells (hUC-MSCs), isolated from discarded extra-embryonic tissue after birth, are promising candidate source of mesenchymal stem cells (MSCs). Apart from their advantages in abundant supply, painless collection, and faster self-renewal, hUC-MSCs have shown the potencies to differentiate into a variety of cells of three germ layer; hUC-MSCssynthesize and secret a set of trophic factors and cytokines to migrate toward inflammatory tissues such as cancer tissues. This work was divided into two parts; in vitro work which involves human breast adenocarcinoma coculturewith human Wharton jellymesenchymal stem cells and in vivo work which involved transplantation of isolated hUC-MSCs into induced experimental mice with breast adenocarcinoma. We assessed cell proliferation by MTT assay, genes expression (TLR4, NF-KB, VEGF, IL-1, IL8) byqRT-PCRboth in vivo and in vitro, the level of IL-6 and JNK by ELISA technique from in vitro cultured conditioned media. As regard cell proliferation assay there was significant decrease in breast carcinoma groups compared to all other treated cancer groups.As regard genes expression there was significant decrease in (TLR4, NF-KB, VEGF, IL1and IL-8) genes and significant decrease in (IL-6, JNK) level which are responsible for development and progression of cancer, in breast carcinoma groups compared to all other treated cancer groups.Better results were obtained by addition of doxorubicin toMSCSin treatment of breast carcinoma. HUC-MSCS can be applied in breast carcinoma treatment, as it affects the mechanism of tumor regression through modulation of different genes and cytokines expression which are involved in tumor initiation and progression. But much better results were obtained on combination between MSCS and doxorubicin for breast cancer treatment.