Sorafenib Plus Ixabepilone as First-Line Treatment of Metastatic HER2-Negative Breast Cancer: A Sarah Cannon Research Institute Phase I/II Trial

Diverse roles of tumor-stromal PDGFB-to-PDGFRβ signaling in breast cancer growth and metastasis

Over the last couple of decades, it has become increasingly apparent that the tumor microenvironment (TME) mediates every step of cancer progression and solid tumors are only able to metastasize with a permissive TME. This intricate interaction of cancer cells with their surrounding TME, or stroma, is becoming more understood with an ever greater knowledge of tumor-stromal signaling pairs such as platelet-derived growth factors (PDGF) and their cognate receptors. We and others have focused our research efforts on understanding how tumor-derived PDGFB activates platelet-derived growth factor receptor beta (PDGFRβ) signaling specifically in the breast cancer TME. In this chapter, we broadly discuss PDGF and PDGFR expression patterns and signaling in normal physiology and breast cancer. We then detail the expansive roles played by the PDGFB-to-PDGFRβ signaling pathway in modulating breast tumor growth and metastasis with a focus on specific cellular populations within the TME, which are responsive to tumor-derived PDGFB. Given the increasingly appreciated importance of PDGFB-to-PDGFRβ signaling in breast cancer progression, specifically in promoting metastasis, we end by discussing how therapeutic targeting of PDGFB-to-PDGFRβ signaling holds great promise for improving current breast cancer treatment strategies.

Targeting Angiogenesis in Breast Cancer: Current Evidence and Future Perspectives of Novel Anti-Angiogenic Approaches

Angiogenesis is a vital process for the growth and dissemination of solid cancers. Numerous molecular pathways are known to drive angiogenic switch in cancer cells promoting the growth of new blood vessels and increased incidence of distant metastasis. Several angiogenesis inhibitors are clinically available for the treatment of different types of advanced solid cancers. These inhibitors mostly belong to monoclonal antibodies or small-molecule tyrosine kinase inhibitors targeting the classical vascular endothelial growth factor (VEGF) and its receptors. Nevertheless, breast cancer is one example of solid tumors that had constantly failed to respond to angiogenesis inhibitors in terms of improved survival outcomes of patients. Accordingly, it is of paramount importance to assess the molecular mechanisms driving angiogenic signaling in breast cancer to explore suitable drug targets that can be further investigated in preclinical and clinical settings. This review summarizes the current evidence for the effect of clinically available anti-angiogenic drugs in breast cancer treatment. Further, major mechanisms associated with intrinsic or acquired resistance to anti-VEGF therapy are discussed. The review also describes evidence from preclinical and clinical studies on targeting novel non-VEGF angiogenic pathways in breast cancer and several approaches to the normalization of tumor vasculature by targeting pericytes, utilization of microRNAs and extracellular tumor-associate vesicles, using immunotherapeutic drugs, and nanotechnology.

Potential Synthetic Lethality for Breast Cancer: A Selective Sirtuin 2 Inhibitor Combined with a Multiple Kinase Inhibitor Sorafenib

Sorafenib is a clinically useful multiple kinase inhibitor for the treatment of kidney cancer, liver cancer and acute myelocytic leukemia, while it has shown weak efficacy in suppressing breast cancer. Since sirtuin2 (SIRT2) is an important epigenetic regulator and associated with several cancer types including breast cancer, development and evaluation of new SIRT2 inhibitors to probe their therapeutic potentials is currently desirable. A highly selective SIRT2 inhibitor named I was previously developed by us, which showed activity to inhibit non-small cell lung cancer cell lines in vitro. We herein report expanded screening of I and its structurally similar inactive compound II against other cancer cell lines, and found that I had a wide spectrum of anticancer activity while II had no such effects. The I-sorafenib combination treatment exerted obvious synergistic reduction on cell viability of MCF-7 cells. We observed that the combination treatment could suppress cell proliferation, survival and migration, arrest cell cycle at G0/G1 phase, and induce apoptosis in MCF-7 cells, when compared with the single treatment. In vivo studies revealed that the combination treatment showed stronger tumor growth inhibition (87%), comparing with I-(42.8%) or sorafenib-solely-treated groups (61.1%) in MCF-7 xenograft model. In conclusion, this work clearly revealed a potential synthetic lethality effect for I combined with sorafenib, and will probably offer a new strategy at least for breast cancer treatment.

SIRT6 silencing overcomes resistance to sorafenib by promoting ferroptosis in gastric cancer

Sorafenib is a tyrosine kinase inhibitor that shows anti-tumour effects against various cancers including gastric cancer (GC). However, the clinical application of sorafenib is often hampered by drug resistance. Sirtuins 6 (SIRT6) is a member of the Sirtuin family of NAD (+)-dependent enzymes that are critically involved in various biological activities. This study presents that SIRT6 silencing overcomes sorafenib resistance by promoting ferroptosis, which is a novel form of cell death. Mechanistically, SIRT6 inhibition led to the inactivation of the Keap1/Nrf2 signalling pathway and downregulation of GPX4. The overexpression of GPX4 or activation of Keap1/Nrf2 reverses the effects of the downregulation of SIRT6 on sorafenib-induced ferroptosis. Thus, targeting the SIRT6/Keap1/Nrf2/GPX4 signalling pathway may be a potential strategy for overcoming sorafenib resistance in GC.

Ixabepilone: Overview of Effectiveness, Safety, and Tolerability in Metastatic Breast Cancer

Treatment algorithms for metastatic breast cancer describe sequential treatment with chemotherapy and, if appropriate, targeted therapy for as long as the patient receives benefit. The epothilone ixabepilone is a microtubule stabilizer approved as a monotherapy and in combination with capecitabine for the treatment of metastatic breast cancer in patients with demonstrated resistance to anthracyclines and taxanes. While chemotherapy and endocrine therapy form the backbone of treatment for metastatic breast cancer, the epothilone drug class has distinguished itself for efficacy and safety among patients with disease progression during treatment with chemotherapy. In phase III trials, ixabepilone has extended progression-free survival and increased overall response rates, with a manageable toxicity profile. Recent analyses of subpopulations within large pooled datasets have characterized the clinical benefit for progression-free survival and overall survival for ixabepilone in special populations, such as patients with triple-negative breast cancer or those who relapsed within 12 months of prior treatment. Additional investigation settings for ixabepilone therapy discussed here include adjuvant therapy, weekly dosing schedules, and ixabepilone in new combinations of treatment. As with other microtubule stabilizers, ixabepilone treatment can lead to peripheral neuropathy, but evidence-based management strategies may reverse these symptoms. Dose reductions did not appear to have an impact on the efficacy of ixabepilone plus capecitabine. Incorporation of ixabepilone into individualized treatment plans can extend progression-free survival in a patient population that continues to represent an unmet need.

Pterostilbene enhances sorafenib's anticancer effects on gastric adenocarcinoma

Sorafenib has been approved for the treatment of certain cancers in clinic. However, the effects of sorafenib on gastric adenocarcinoma (GAC) were still limited. This study aimed to evaluate both in vitro and in vivo efficacy of sorafenib in combination with pterostilbene (PTE) on the treatment of GAC. Here, the morphological changes and cell viability were recorded in both N87 and MKN45 cells. The cell cycle profile and apoptosis were assessed by flow cytometry. Subcutaneous tumour xenografts were constructed in nude mice, and IHC staining of the dissected tumour tissues was conducted. Our results showed that PTE enhanced sorafenib's inhibitory effects on cell viability. The obvious down‐regulation of cyclin D1, Cdk‐2, Cdk‐4, Cdk‐6 and p62 and the up‐regulation of LC3II, caspase‐9, caspase‐3 and PARP cleavages were observed for the combination treatment with PTE and sorafenib than monotherapy. The combination treatment resulted in a higher level of cell cycle arrest at G1 phase and apoptosis than either drug. Besides, drug combination significantly enhanced the inhibition of tumour growth than sorafenib or PET alone in nude mice. The percentage of Ki‐67‐ and PCNA‐positive cells was distinctly reduced, and the apoptotic cells was obviously increased when compared with single drug therapy. Altogether, PET obviously enhanced sorafenib's antitumour effects against GAC through inhibiting cell proliferation, inducing autophagy and promoting apoptosis. The combination therapy with PET and sorafenib may serve as a novel therapeutic strategy for treating GAC and deserve further clinical trials.

Transferrin-Modified Nanoliposome Codelivery Strategies for Enhancing the Cancer Therapy

Chemotherapy remains one of the most effective treatments for many cancers in a clinic. At present, various targets have been used to modify the PEGylated liposomes for doxorubicin (Dox) delivery, but the antitumor effect of Dox is not satisfactory. Therefore, combination chemotherapeutics has been considered as a promising method to improve tumor treatment. These years, RAF/MEK/ERK-mediated cell signaling pathway has been discovered to inhibit the growth of tumors. Thus, Sorafenib tosylate (Sor) was used in this study, which directly inhibited tumor cell proliferation through blocking RAF/MEK/ERK-mediated cell signaling pathway and indirectly inhibited tumor cell growth through blocking angiogenesis by VEGFR and PDGF. In this article, we develop a "combination delivery system" to deliver the hydrophobic drug (Sor) in phospholipid bilayer and hydrophilic drug (Dox) in inner cores for enhancing the antitumor effect. Moreover, in vitro experiments verified whether the physicochemical properties of carriers were stable and transferrin-modified liposomes displayed the highest uptake. The results of in vivo experiments showed that the codelivery system inhibited the tumor growth more effectively than monotherapy. Overall, this combination delivery system for delivering the hydrophobic and hydrophilic drugs simultaneously may offer a novel strategy for breast cancer treatment and provide a reference for the possibility of clinical usage.

Chemotherapeutic agents for the treatment of metastatic breast cancer: An update

Breast cancer is the second greatest cause of death among women worldwide; it comprises a group of heterogeneous diseases that evolves due to uncontrolled cellular growth and differentiation and the loss of normal programmed cell death. There are different molecular sub-types of breast cancer; therefore, various options are selected for treatment of different forms of metastatic breast cancer. However, the use of chemotherapeutic drugs is usually accompanied by deleterious side effects and the development of drug resistance when applied for a longer period. This review offers a classification of these chemotherapeutic agents according to their modes of action and therefore improves the understanding of molecular targets that are affected during treatment. Overall, it will allow the clinician to identify more specific targets to increase the effectiveness of a drug and to reduce general toxicity, resistance and other side effects.

Sorafenib for the treatment of breast cancer

INTRODUCTION

Breast cancer treatment includes many options depending on the tumor clinicopathological profile, which groups breast cancer into various subtypes. Bevacizumab is currently the only drug capable of targeting angiogenesis in breast cancer. Sorafenib has also been studied in combination with other agents. Areas covered: Pharmacological aspects of sorafenib, including results from preclinical studies on breast cancer cells; findings about clinical efficacy and safety in both single-arm and randomized clinical trials; ongoing trials. Expert opinion: Since sorafenib as a single agent has shown limited efficacy in breast cancer, its combination with other drugs is under investigation. Dose reduction is the main challenge when sorafenib is combined with chemotherapy or endocrine therapy. Although randomized phase-II trials on sorafenib plus chemotherapy versus chemotherapy alone have shown potential benefits in progression-free survival, preliminary results from a phase-III study in combination with capecitabine are negative. The definitive results of this trial and results from other ongoing phase-II trials will determine further developments of sorafenib in breast cancer. Although these additional data could help determine the most appropriate dose, drug combination and patient settings, a confirmation of the preliminary negative results reported in the phase-III trial are likely to discourage further use of sorafenib in breast cancer, given its non-negligible toxicity, lack of predicting markers, and the number of more promising drugs for breast cancer.

Sorafenib in breast cancer treatment: A systematic review and overview of clinical trials

AIM

To evaluate the current role of sorafenib, an oral multikinase inhibitor in the treatment of breast cancer.

METHODS

An extensive search of the literature until March 2016 was carried out in Medline and clinicaltrials.gov, by using the search terms "sorafenib" and "breast cancer". Papers found were checked for further relevant publications. Overall, 21 relevant studies were found, 18 in advanced breast cancer (16 in stage IV and two in stages III-IV) and three in early breast cancer.

RESULTS

Among studies in advanced breast cancer, there were two trials with sorafenib as monotherapy, four trials of sorafenib in combination with taxanes, two in combination with capecitabine, one with gemcitabine and/or capecitabine, one with vinorelbine, one with bevacizumab, one with pemetrexed and one with ixabepilone, three trials of sorafenib in combination with endocrine therapy and two trials in women with brain metastases undergoing whole brain radiotherapy. In addition, there was one trial of sorafenib added to standard chemotherapy in the adjuvant setting, and two trials in the neoadjuvant setting. In general, sorafenib was well tolerated in breast cancer patients, though its dosage had to be adjusted in some trials, and discontinuation rates were high, particularly for the combination of sorafenib with anastrozole. Sorafenib monotherapy and combinations with taxanes, bevacizumab and ixabepilone showed inadequate efficacy, while efficacy results from combinations with gemcitabine and/or capecitabine and possibly tamoxifen were more promising.

CONCLUSION

At present, sorafenib should not be used for the treatment of breast cancer outside of clinical trials and more clinical data are needed in order to support its standard use in breast cancer therapy.