Devita, Hellman, and Rosenberg's Cancer

LWBK1006-03 LWW-Govindan-Review November 24, 2011 11:19

Chapter 3•Etiology of Cancer Part 1 55

such as the TLRs. Once activated, these cells secrete many proinflam-

matory cytokines such as IL-12, TNF, and IL-6. The activated DCs migrate

to the regional lymph nodes and present antigens acquired in the tissues

to T cells in the context of major histocompatibility complex class I and

II antigens. Thus, through the production of cytokines and activation of

T cells, DCs activate both innate and adaptive immunity in response to

changes in the tissue homeostasis. DCs in tumors are generally hypore-

sponsive because of their interaction with other inflammatory cells or

the tumor cells and therefore are not involved in immune surveillance.

Activation of DCs is one of the immune strategies being pursued in the

treatment of some cancers.

Answer 3.48. The answer is C.

TAMs are derived from monocytes and monocyte precursors from the

blood. TAMs have the capacity to induce either cytotoxic and antitu-

mor or protumor and proangiogenic effects. In most progressing tumors,

TAMs mediate protumor effects They favor tumor growth by producing

growth factors, angiogenic cytokines, and expression of MMPs, TGF,

and TNF that help tumor invasion and metastasis. IL-10 produced by

inflammatory cells, including the TAMs, has an immunosuppressive effect

on TAMs that impair the antitumor effects of these cells.

Answer 3.49. The answer is D.

TLRs are evolutionary conserved molecules that are a family of at least 12

different pattern-recognizing receptors. TLRs are important in recogni-

tion of microbes, pathogens, and endogenous ligands that have a role

in regulation of inflammation. The role of TLRs and other pattern-

recognizing receptors in tumor-associated inflammation remains to be

defined. TLRs expressed on tumor cells can cause apoptosis, but activa-

tion of TLRs on tumor-infiltrating cells may promote tumor progression.