The arsenal of treatments for most cancers fit broadly into the categories of surgery, chemotherapy, radiation, and targeted therapy. All represent proven and successful strategies, yet each can trigger local (tumor) and systemic (host) processes that elicit unwanted, often opposing, influences on cancer growth. Under certain conditions, nearly all cancer treatments can facilitate metastatic spread, often in parallel (and sometimes in clear contrast) with tumor reducing benefits. The paradox of treatment-induced metastasis (TIM) is not new. Supporting preclinical studies span decades, but are often overlooked. With recent evidence of prometastatic effects following treatment with targeted agents blocking the tumor microenvironment, a closer inspection of this literature is warranted. The TIM phenomena may diminish the impact of effective therapies and play a critical role in eventual resistance. Alternatively, it may simply exemplify the gap between animal and human studies, and therefore have little impact for patient disease and treatment. This review will focus on the preclinical model systems used to evaluate TIM and explore the mechanisms that influence overall treatment efficacy. Understanding the role of TIM in established and emerging drug treatment strategies may help provide rationales for future drug combination approaches with antimetastatic agents to improve outcomes and reduce resistance. Cancer Res; 75(17); 1–9. ©2015 AACR.

Natural killer (NK) immune cells mediate antibody-dependent cellular cytotoxicity (ADCC) by aggregating FcγRIIIA/CD16, contributing significantly to the therapeutic effect of CD20 monoclonal antibodies (mAb). In this study, we show that CD16 ligation on primary human NK cells by the anti-CD20 mAb rituximab or ofatumumab stably impairs the spontaneous cytotoxic response attributable to cross-tolerance of several unrelated NK-activating receptors (including NKG2D, DNAM-1, NKp46, and 2B4). Similar effects were obtained from NK cells isolated from patients with chronic lymphocytic leukemia in an autologous setting. NK cells rendered hyporesponsive in this manner were deficient in the ability of these cross-tolerized receptors to phosphorylate effector signaling molecules critical for NK cytotoxicity, including SLP-76, PLCγ2, and Vav1. These effects were associated with long-lasting recruitment of the tyrosine phosphatase SHP-1 to the CD16 receptor complex. Notably, pharmacologic inhibition of SHP-1 with sodium stibogluconate counteracted CD20 mAb-induced NK hyporesponsiveness, unveiling an unrecognized role for CD16 as a bifunctional receptor capable of engendering long-lasting NK cell inhibitory signals. Our work defines a novel mechanism of immune exhaustion induced by CD20 mAb in human NK cells, with potentially negative implications in CD20 mAb-treated patients where NK cells are partly responsible for clinical efficacy. Cancer Res; 75(19); 1–12. ©2015 AACR.

Natural killer (NK) immune cells mediate antibody-dependent cellular cytotoxicity (ADCC) by aggregating FcγRIIIA/CD16, contributing significantly to the therapeutic effect of CD20 monoclonal antibodies (mAb). In this study, we show that CD16 ligation on primary human NK cells by the anti-CD20 mAb rituximab or ofatumumab stably impairs the spontaneous cytotoxic response attributable to cross-tolerance of several unrelated NK activating receptors (including NKG2D, DNAM-1, NKp46 and 2B4). Similar effects were obtained from NK cells isolated from chronic lymphocytic leukemia (CLL) patients in an autologous setting. NK cells rendered hyporesponsive in this manner were deficient in the ability of these cross-tolerized receptors to phosphorylate effector signaling molecules critical for NK cytotoxicity, including SLP-76, PLCγ2 and Vav1. These effects were associated with long-lasting recruitment of the tyrosine phosphatase SHP-1 to the CD16 receptor complex. Notably,
pharmacological inhibition of SHP-1 with sodium stibogluconate counteracted CD20 mAb-induced NK hyporesponsiveness, unveiling an unrecognized role for CD16 as a bifunctional receptor capable of engendering long-lasting NK cell inhibitory signals. Our work defines a novel mechanism of immune exhaustion induced by CD20 mAb in human NK cells, with potentially negative implications in CD20 mAb-treated patients where NK cells are partly responsible for clinical efficacy. –

Mitochondrial DNA (mtDNA), encoding 13 out of more than 1,000 proteins of the mitochondrial proteome, is of paramount importance for the bioenergetic machinery of oxidative phosphorylation that is required for tumor initiation, propagation, and metastasis. In stark contrast to the widely held view that mitochondria and mtDNA are retained and propagated within somatic cells of higher organisms, recent in vitro and in vivo evidence demonstrates that mitochondria move between mammalian cells. This is particularly evident in cancer where defective mitochondrial respiration can be restored and tumor-forming ability regained by mitochondrial acquisition. This paradigm shift in cancer cell biology and mitochondrial genetics, concerning mitochondrial movement between cells to meet bioenergetic needs, not only adds another layer of plasticity to the armory of cancer cells to correct damaged mitochondria, but also points to potentially new therapeutic approaches. Cancer Res; 75(16); 1–6. ©2015 AACR.

Cancer cells commonly display aberrant surface glycans and related glycoconjugate scaffolds. Compared with their normal counterparts, cancer cell glycans are variably produced and often structurally distinct, serving as biomarkers of cancer progression or as functional entities to malignancy. The glycan signature of a cancer cell is created by the collaborative activities of glycosyltransferases, glycosidases, nucleotide-sugar transporters, sulfotransferases, and glycan-bearing protein/lipid scaffolds. In a coordinated fashion, these factors regulate the synthesis of cancer cell glycans and thus are considered correlates of cancer cell behavior. Functionally, cancer cell glycans can serve as binding targets for endogenous lectin effectors, such as C-type selectins and S-type galectins. There has been a recent surge of important observations of the role of glycosytransferases, specifically α2,6 sialyltransferases, in regulating the length and lectin-binding features of serine/threonine (O)-glycans found on cancer cells. The capping activity of O-glycan–specific α2,6 sialyltransferases, in particular, has been found to regulate cancer growth and metastasis in a galectin-dependent manner. These findings highlight the functional importance of cancer cell O-glycans and related galectin-binding features in the virulent activity of cancer and raise the prospect of targeting cancer cell glycans as effective anticancer therapeutics. Cancer Res; 75(16); 1–8. ©2015 AACR.