Tumor-associated Macrophages (TAMs) in Cancer Resistance; Modulation by Natural Products.

Tumor-associated macrophages (TAMs) play a pivotal role in the progression and resistance of tumors to different anticancer drugs. TAMs can modulate the tumor microenvironment (TME) in favor of immune system exhaustion. The interactions of TAMs with TME can affect the function of cytotoxic CD8+ T lymphocytes (CTLs) and natural killer (NK) cells. Furthermore, TAMs can induce cancer cell proliferation by releasing some growth factors, such as transforming growth factor (TGF)-ß. TAMs have several positive cross-talks with other immune suppressive cells such as regulatory T cells (Tregs), myeloid-derived suppressor cells (MDSCs), cancerassociated fibroblasts (CAFs), and cancer cells, leading to the release of growth factors, the proliferation of cancer cells and tumor growth. These interactions also can induce invasion and migration of cancer cells, angiogenesis, and metastasis. The inhibition of TAMs is an intriguing strategy for overcoming tumor resistance and suppression of cancer cells. Some natural-derived agents such as melatonin, curcumin, resveratrol, apigenin, and other flavonoids have shown the ability to modulate TME, including TAMs. These adjuvants may be able to boost antitumor immunity through the modulation of TAMs. This review explains the modulatory effects of some well-known naturally derived agents on the activity of TAMs. The modulation of TAMs by these agents may be useful in suppressing tumor growth and invasion.

Mesenchymal stem cell-released oncolytic virus: an innovative strategy for cancer treatment.

Oncolytic viruses (OVs) infect, multiply, and finally remove tumor cells selectively, causing no damage to normal cells in the process. Because of their specific features, such as, the ability to induce immunogenic cell death and to contain curative transgenes in their genomes, OVs have attracted attention as candidates to be utilized in cooperation with immunotherapies for cancer treatment. This treatment takes advantage of most tumor cells' inherent tendency to be infected by certain OVs and both innate and adaptive immune responses are elicited by OV infection and oncolysis. OVs can also modulate tumor microenvironment and boost anti-tumor immune responses. Mesenchymal stem cells (MSC) are gathering interest as promising anti-cancer treatments with the ability to address a wide range of cancers. MSCs exhibit tumor-trophic migration characteristics, allowing them to be used as delivery vehicles for successful, targeted treatment of isolated tumors and metastatic malignancies. Preclinical and clinical research were reviewed in this study to discuss using MSC-released OVs as a novel method for the treatment of cancer. Video Abstract.