“Iron-saturated” bovine lactoferrin improves the chemotherapeutic effects of tamoxifen in the treatment of basal-like breast cancer in mice

Xueying Sun,Shiva Reddy,Ruohan Jiang,Kate P Palmano,Aneta Przepiorski,Geoffrey W Krissansen

doi:10.1186/1471-2407-12-591

Abstract

BackgroundTamoxifen is used in hormone therapy for estrogen-receptor (ER)-positive breast cancer, but also has chemopreventative effects against ER-negative breast cancers. This study sought to investigate whether oral iron-saturated bovine lactoferrin (Fe-Lf), a natural product which enhances chemotherapy, could improve the chemotherapeutic effects of tamoxifen in the treatment of ER-negative breast cancers.MethodsIn a model of breast cancer prevention, female Balb/c mice treated with tamoxifen (5 mg/Kg) were fed an Fe-Lf supplemented diet (5 g/Kg diet) or the base diet. At week 2, 4T1 mammary carcinoma cells were injected into an inguinal mammary fat pad. In a model of breast cancer treatment, tamoxifen treatment was not started until two weeks following tumor cell injection. Tumor growth, metastasis, body weight, and levels of interleukin 18 (IL-18) and interferon γ (IFN-γ) were analyzed.ResultsTamoxifen weakly (IC50 ~ 8 μM) inhibited the proliferation of 4T1 cells at pharmacological concentrations in vitro. In the tumor prevention study, a Fe-Lf diet in combination with tamoxifen caused a 4 day delay in tumor formation, and significantly inhibited tumor growth and metastasis to the liver and lung by 48, 58, and 66% (all P < 0.001), respectively, compared to untreated controls. The combination therapy was significantly (all P < 0.05) more effective than the respective monotherapies. Oral Fe-Lf attenuated the loss of body weight caused by tamoxifen and cancer cachexia. It prevented tamoxifen-induced reductions in serum levels of IL-18 and IFN-γ, and intestinal cells expressing IL-18 and IFN-γ. It increased the levels of Lf in leukocytes residing in gut-associated lymphoid tissues. B, T and Natural killer (NK) cells containing high levels of Lf were identified in 4T1 tumors, suggesting they had migrated from the intestine. Similar effects of Fe-Lf and tamoxifen on tumor cell viability were seen in the treatment of established tumors.ConclusionsThe results indicate that Fe-Lf is a potent natural adjuvant capable of augmenting the chemotherapeutic activity of tamoxifen. It could have application in delaying relapse in tamoxifen-treated breast cancer patients who are at risk of developing ER-negative tumors.

Highlights

Tamoxifen is used in hormone therapy for estrogen-receptor (ER)-positive breast cancer, and has chemopreventative effects against ER-negative breast cancers
Bovine Iron-saturated lactoferrin (Fe-Lf) augments tamoxifen therapy to inhibit the formation and growth of basal-like breast tumors Groups of Balb/c mice were placed on either the control diet or the Fe-Lf diet, and received injections of either PBS or tamoxifen every two days to determine whether Fe-Lf would augment the effects of tamoxifen in preventing the formation of breast tumors (Figure 1A)
Neither the Fe-Lf nor tamoxifen monotherapies delayed the appearance of palpable 4T1 tumors, whereas in contrast the combination of the Fe-Lf diet and tamoxifen delayed the appearance of palpable tumors by 4 days, and inhibited their growth compared with the control diet (Figure 2A)

Summary

Introduction

Tamoxifen is used in hormone therapy for estrogen-receptor (ER)-positive breast cancer, and has chemopreventative effects against ER-negative breast cancers. Tamoxifen treatment downregulates the expression of the cytokine interleukin (IL)-18 [9], lowers the numbers of CD4+ T cells [10], and reduces natural killer (NK) cell activity [10] It inhibits the functions of monocytes, antibody formation, dendritic cell differentiation and activation, and reduces lymphoid organ weights in rodents [11,12,13,14]. It upregulates the expression of the potently immunosuppressive cytokine transforming growth factor (TGF)-β1 in breast tumors, which tumors use to avoid the immune response, and is implicated in the failure of tamoxifen therapy [15]. Upregulation of TGF-β1 is seen with the ER antagonist fulvestrant, suggesting it may be a common feature of several anti-estrogens [16]

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