Figure 1.

Intermittent hypoxia (IH) facilitates lung cancer progression by mediating tumor-associated macrophages (TAMs). (A) Comparison of TAMs in room air (RA) and IH groups. (i) In the RA group, TAMs are present in the connective tissue surrounding the tumor (brown arrow). (ii) In the IH group, in the IH state, the invasion of lung cancer is enhanced, and TAMs are present in the connective tissue (brown arrow) and muscle (black arrow) surrounding the tumor (67). (B) Effects of IH and oophorectomy (OVX) on invasion and distant metastasis of lung cancer in mice. (i) In IH, the primary lung cancer (white arrow) infiltrates the skeletal muscle (yellow arrow). (ii) When exposed to both IH and OVX, lung cancer metastases (white arrows) increased (68). (C) The invasive and metastatic potential of lung cancer in IH and RA are compared. (i) RA group (left), no invasion; IH group (right side), lung cancer invading muscle tissue. Cancer cells (yellow arrows), muscle cells (white arrows). (ii) IH stimulates lung cancer metastasis, and the yellow arrow indicates metastatic lesions (69). Reprinted with permission from Ref (67–69).