Contributing Editor: Marjolein van Egmond, Ph.D; Department of Surgery and the Department of Molecular Cell Biology and Immunology, VU University Medical Center, Amsterdam, The Netherlands. doi: 10.14229/ONCO.2014.4.16.002
Monoclonal antibodies (mAbs) are a valuable addition to the current arsenal of anti-cancer therapies. We demonstrated that after mAb therapy, circulating tumor cells are removed by macrophages in the liver via antibody-dependent phagocytosis. Importantly, this prevented the development of liver metastases. Our discovery extends the knowledge on mode(s) of action of mAb therapy, and may help to optimize mAb-based anticancer therapeutics, especially for patients with haematological diseases, and patients undergoing resection of colorectal cancer.
__________
In addition to the more classical treatments with chemo- or radiotherapy to eliminate cancer, many efforts have been made to recruit the patient?s own immune system to target tumor cells. These types of therapies are collectively referred to as immunotherapy. The use of monoclonal antibodies (mAbs) is a prime example of immunotherapy, and increasingly successful in the treatment of a variety of diverse cancers [1][2]
…we envision that addition of mAb therapy to the current treatment of patients with colorectal cancer may have the potential to greatly improve clinical outcome…
mAbs can work via many different modes of actions. For instance, the anti-vascular endothelial growth factor (VEGF) mAb Bevacizumab (Avastin?; Genentech/Roche) inhibits the formation of new blood vessels, which will reduce delivery of nutrients and oxygen to the tumor. Consequently, cancer cells are starved and will die. Other mAbs target tumor cells directly.
The most successful are anti-CD20 mAbs, like rituximab (Rituxan?; Genentech | Biogen IDEC or MabThera?; Roche), that are used to treat patients with B cell malignancies.[3] Other mAbs target Human Epidermal growth factor Receptor 2 (HER-2) (Trastuzumab; Herceptin?; Genentech/Roche) on breast cancer cells or Epidermal Growth Factor Receptor (EGFR) (Cetuximab; Erbitux?; Eli Lilly and Company/Bristol-Myers Squibb Company, or Panitumumab; Vectibix?; Amgen) on colorectal or head and neck cancer cells. mAbs that bind to tumor cells can also employ many different modes of action, which renders it complicated to understand which one (or more) of these mechanisms is the most important in patients. For instance, anti-EGFR mAbs block the binding of the growth factor EGF to EGFR. Blocking this receptor should theoretically prevent cancer cells from growing. Unfortunately, it doesn?t work like that in many patients, because the signaling pathways are deregulated in many cancer cells. Consequently, tumor cells will always receive the signal to divide, even in the absence of the growth factor EGF. In these cases treatment with anti-EFGR mAbs will not work. [4] Another mechanism is the induction of apoptosis or programmed cell death in cancer cells by the mAb, which can be less effective when tumor cells have mutations in apoptotic signaling pathways. [5]
Complement-dependent cytotoxicity
None of the abovementioned mechanisms activates immune responses. However, other additional mechanisms involve recruitment of different components of the immune system. Some mAbs can activate the complement pathway, leading to the induction of complement-dependent cytotoxicity (CDC). [6][7] Furthermore, immune cells express Fc receptors that can bind the Fc tail of mAbs. In this way, mAbs form a bridge between immune cells and cancer cells. [8] It has been shown that subtle changes in the composition of Fc receptors, referred to as polymorphisms, play an important role in the efficacy of treatment, which is a very strong indication that Fc receptors play an important role in patients. For instance, the Fc?RIIIa-158V and Fc?RIIIa-158F allotypes determine affinity for IgG antibodies, and influence clinical outcome after mAb therapy. [9]
Two important immune cell types that express Fc?RIIIa and can act as effector cell in mAb immunotherapy, are natural killer (NK) cells and macrophages. NK cells kill cells through antibody dependent cytotoxicity (ADDC), which leads to apoptosis of cancer cells10.[10] Macrophages use a different mechanism compared to NK cells, as they engulf and digest tumor cells11. [11] This is a mechanism that we refer to as antibody-dependent cellular phagocytosis or ADCP (Figure 1; Click to enlarge). To investigate which cell type was important for in vivo killing of tumor cells, we performed live cell imaging and intravital microscopy. We showed that mAb therapy induced phagocytosis of circulating tumor cells by macrophages of the liver (Kupffer cells), which prevented the development of liver metastases. [12]
As such, we hypothesize that macrophages may play a major role in successes of mAb therapy in especially patients with hematological malignancies. It was demonstrated that patients with an Fc?RIIIa-158V allotype had better clinical responses after rituximab therapy, compared with patients with the Fc?RIIIa-158F allotype. [13] Recently, Montalvao et al. showed with intravital microscopy that rituximab induced the removal of (malignant) B cells by Kupffer cells, as well. [14] However, it is less clear whether macrophages also contribute to tumor cell killing in solid malignancies. In our experiments, mAb therapy was ineffective when given after the establishment of micro-metastases in the liver. Intravital microscopy demonstrated that Kupffer cells were stationary and not recruited, arguing against an important role for Kupffer cells in mAb therapy of existing liver metastases. [12]
Risk of liver metastasis development
Nonetheless, we envision that addition of mAb therapy to the current treatment of patients with colorectal cancer may have the potential to greatly improve clinical outcome. For a long time it has been a concern of the surgeons in our department that the surgery ? which is performed to remove the primary tumor ? might contribute to the risk of liver metastasis development. [15][16] Not only may the severity of the surgery induce immune suppression, but it was also shown that manipulation of the tumor, in order to remove it, can lead to shedding of tumor cells. Disseminated circulating tumor cells were detected at the time of resection of either the primary tumor or liver metastases in the majority of patients. [17] Importantly, presence of circulating tumor cells was associated with disease progression and poorer clinical outcome. [18][19] We previously demonstrated in experimental models that surgery with curative intent paradoxically 
promotes adherence of circulating tumor cells in the liver [20] (Figure 2; Click to enlarge).
Since many patients develop liver metastases after successful resection of the primary colorectal carcinoma at a time when metastatic disease was absent, the negative influence of surgery on tumor cell adhesion in patients is strongly supported. However, surgical removal of the primary tumor is currently the only therapy that can provide long-term disease-free survival, and is therefore an absolute necessity.
We therefore investigated whether mAb therapy can counterbalance this negative effect of surgery, as it may help to eliminate the last remaining cancer cells in the bloodstream. We now show that treatment with anti-EGFR mAbs potently induces ADCP of colon carcinoma cells by Kupffer cells, which prevented the development of liver metastases12,21. [12][21] We therefore propose that patients at risk of developing (recurrent) liver metastases, – such as patients undergoing resection of primary colorectal cancer or resectable liver metastases -, will profoundly benefit from pre-operative mAb adjuvant therapy (Figure 2).
Great promise
Considering that worldwide ~ 1.2 million patients are diagnosed with colorectal cancer each year, with an estimated annual death rate of 600.000 patients, our findings may hold great promise for the treatment of many cancer patients. As such, it is now the highest priority to perform clinical trials to study whether we can remove circulating tumor cells during surgery of patients and investigate if this will prevent the development of liver metastases after the surgery.
For more information:
[1] Sliwkowski MX, Mellman I. Antibody therapeutics in cancer. Science. 2013 Sep 13;341(6151):1192-8. doi: 10.1126/science.1241145. [Article][PubMed]
[2] Scott AM, Wolchok JD, Old LJ. Antibody therapy of cancer. Nat Rev Cancer. 2012 Mar 22;12(4):278-87. doi: 10.1038/nrc3236. [Article][PubMed]
[3] Amoroso A, Hafsi S, Militello L, Russo AE, Soua Z, Mazzarino MC, Stivala F, Libra M. Understanding rituximab function and resistance: implications for tailored therapy. Front Biosci (Landmark Ed). 2011 Jan 1;16:770-82. [Article][PubMed]
[4] Benvenuti S, Sartore-Bianchi A, Di Nicolantonio F, Zanon C, Moroni M, Veronese S, Siena S, Bardelli A. Oncogenic activation of the RAS/RAF signaling pathway impairs the response of metastatic colorectal cancers to anti-epidermal growth factor receptor antibody therapies.Article][PubMed]
[5] Glennie MJ1, French RR, Cragg MS, Taylor RP.Mechanisms of killing by anti-CD20 monoclonal antibodies. Mol Immunol. 2007 Sep;44(16):3823-37.[Article][PubMed]
[6] Kolev M, Towner L, Donev R. Complement in cancer and cancer immunotherapy. Arch Immunol Ther Exp (Warsz). 2011 Dec;59(6):407-19. doi: 10.1007/s00005-011-0146-x. Epub 2011 Sep 30.[Article][PubMed]
[7] Racila E, Link BK, Weng WK, Witzig TE, Ansell S, Maurer MJ, Huang J, Dahle C, Halwani A, Levy R, Weiner GJ. A polymorphism in the complement component C1qA correlates with prolonged response following rituximab therapy of follicular lymphoma. Clin Cancer Res. 2008 Oct 15;14(20):6697-703. doi: 10.1158/1078-0432.CCR-08-0745.[Article][PubMed]
[8] Nimmerjahn F, Ravetch JV. Antibodies, Fc receptors and cancer. Curr Opin Immunol. 2007 Apr;19(2):239-45. Epub 2007 Feb 8.[Article][PubMed]
[9] Overdijk, MB, Verploegen, S., Bleeker, WK, Parren, P. W. (2014) Role of IgG Fc Receptors in monoclonal antibody therapy of cancer. Chapter 13, Antibody Fc: Linking Adaptive and Innate Immunity, . Elsevier.[Publication]
[10] Zamai L, Ponti C, Mirandola P, Gobbi G, Papa S, Galeotti L, Cocco L, Vitale M. NK cells and cancer. J Immunol. 2007 Apr 1;178(7):4011-6 [Article][PubMed]
[11] Braster R, O’Toole T, van Egmond M. Myeloid cells as effector cells for monoclonal antibody therapy of cancer. Methods. 2014 Jan 1;65(1):28-37. doi: 10.1016/j.ymeth.2013.06.020. Epub 2013 Jun 27.[Article][PubMed]
[12] G?l N, Babes L, Siegmund K, Korthouwer R, B?gels M, Braster R, Vidarsson G, ten Hagen TL, Kubes P, van Egmond M. Macrophages eliminate circulating tumor cells after monoclonal antibody therapy. J Clin Invest. 2014 Feb 3;124(2):812-23. doi: 10.1172/JCI66776. Epub 2014 Jan 16.[Article][PubMed]
[13] Weng WK, Levy R. Two immunoglobulin G fragment C receptor polymorphisms independently predict response to rituximab in patients with follicular lymphoma. J Clin Oncol. 2003 Nov 1;21(21):3940-7. Epub 2003 Sep 15. [Article][PubMed]
[14] Montalvao F, Garcia Z, Celli S, Breart B, Deguine J, Van Rooijen N, Bousso P. The mechanism of anti-CD20-mediated B cell depletion revealed by intravital imaging. J Clin Invest. 2013 Dec 2;123(12):5098-103. doi: 10.1172/JCI70972. Epub 2013 Nov 1 [Article][PubMed]
[15] Van der Bij GJ, Oosterling SJ, Beelen RH, Meijer S, Coffey JC, Van Egmond M. The perioperative period is an underutilized window of therapeutic opportunity in patients with colorectal cancer. Ann Surg. 2009 May;249(5):727-34. doi: 10.1097/SLA.0b013e3181a3ddbd.[Article][PubMed]
[16] Coffey JC, Wang JH, Smith MJ, Bouchier-Hayes D, Cotter TG, Redmond HP. Excisional surgery for cancer cure: therapy at a cost. Lancet Oncol. 2003 Dec;4(12):760-8.[Article][PubMed]
[17] Wind J, Tuynman JB, Tibbe AG, Swennenhuis JF, Richel DJ, van Berge Henegouwen MI, Bemelman WA. Circulating tumour cells during laparoscopic and open surgery for primary colonic cancer in portal and peripheral blood. Eur J Surg Oncol. 2009 Sep;35(9):942-50. doi: 10.1016/j.ejso.2008.12.003. Epub 2009 Jan 18 [Article][PubMed]
[18] Rahbari NN, Aigner M, Thorlund K, Mollberg N, Motschall E, Jensen K, Diener MK, B?chler MW, Koch M, Weitz J. Meta-analysis shows that detection of circulating tumor cells indicates poor prognosis in patients with colorectal cancer. Gastroenterology. 2010 May;138(5):1714-26. doi: 10.1053/j.gastro.2010.01.008. Epub 2010 Jan 25. [Article][PubMed]
[19] Groot Koerkamp B, Rahbari NN, B?chler MW, Koch M, Weitz J. Circulating tumor cells and prognosis of patients with resectable colorectal liver metastases or widespread metastatic colorectal cancer: a meta-analysis. Ann Surg Oncol. 2013 Jul;20(7):2156-65. doi: 10.1245/s10434-013-2907-8. Epub 2013 Mar 2 [Article][PubMed]
[20] G?l N, B?gels M, Grewal S, van der Meer AJ, Rojas LB, Fluitsma DM, van den Tol MP, et al. Surgery-induced reactive oxygen species enhance colon carcinoma cell binding by disrupting the liver endothelial cell lining. Gut. 2011 Aug;60(8):1076-86. doi: 10.1136/gut.2010.224717. Epub 2011 Jan 27.[Article][PubMed]
[21] Van der Bij GJ, B?gels M, Otten MA, Oosterling SJ, Kuppen PJ, Meijer S, Beelen RH, Van Egmond M. Experimentally induced liver metastases from colorectal cancer can be prevented by mononuclear phagocyte-mediated monoclonal antibody therapy.J Hepatol. 2010 Oct;53(4):677-85. doi: 10.1016/j.jhep.2010.04.023. Epub 2010 Jun 17.[Article][PubMed]
Copyright ? 2014 InPress Media Group/Sunvalley Communication. All rights reserved. Republication or redistribution of InPress Media Group/Sunvalley Communication content, including by framing or similar means, is expressly prohibited without the prior written consent ofInPress Media Group/Sunvalley Communication. InPress Media Group/Sunvalley Communication shall not be liable for any errors or delays in the content, or for any actions taken in reliance thereon. Onco’Zine and Oncozine are registered trademarks and trademarks of Sunvalley Communication around the world.
