Bosutinib in combination with the aromatase inhibitor exemestane: a phase II trial in postmenopausal women with previously treated locally advanced or metastatic hormone receptor-positive/HER2-negative breast cancer

Aromatase inhibition plus/minus Src inhibitor saracatinib (AZD0530) in advanced breast cancer therapy (ARISTACAT): a randomised phase II study

PURPOSE

The development of oestrogen resistance is a major challenge in managing hormone-sensitive metastatic breast cancer. Saracatinib (AZD0530), an oral Src kinase inhibitor, prevents oestrogen resistance in animal models and reduces osteoclast activity. We aimed to evaluate the efficacy of saracatinib addition to aromatase inhibitors (AI) in patients with hormone receptor-positive metastatic breast cancer.

METHODS

This phase II multicentre double-blinded randomised trial allocated post-menopausal women to AI with either saracatinib or placebo (1:1 ratio). Patients were stratified into an "AI-sensitive/naïve" group who received anastrozole and "prior-AI" group who received exemestane. Primary endpoint was progression-free survival (PFS). Secondary endpoints included overall survival (OS), objective response rate (ORR) and toxicity.

RESULTS

140 patients were randomised from 20 UK centres to saracatinib/AI (n = 69) or placebo/AI (n = 71). Saracatinib was not associated with an improved PFS (3.7 months v. 5.6 months placebo/AI) and did not reduce likelihood of bony progression. There was no benefit in OS or ORR. Effects were consistent in "AI-sensitive/naive" and "prior-AI" sub-groups. Saracatinib was well tolerated with dose reductions in 16% and the main side effects were gastrointestinal, hypophosphatemia and rash.

CONCLUSION

Saracatinib did not improve outcomes in post-menopausal women with metastatic breast cancer. There was no observed beneficial effect on bone metastases. CRUKE/11/023, ISRCTN23804370.

A phase I trial of palbociclib and bosutinib with fulvestrant in patients with metastatic hormone receptor positive and HER2 negative (HR+ HER2-) breast cancer refractory to an aromatase inhibitor and a CDK4/6 inhibitor

Standard treatment for metastatic hormone positive (HR+) breast cancer includes a combination of a CDK4/6 inhibitor and antiestrogen therapy. Despite durable responses, eventual endocrine resistance results in disease progression. The Src/Abl pathway has been shown to mediate endocrine resistance in breast cancer, thus providing a promising target for novel therapies. Bosutinib is a tyrosine kinase inhibitor that targets the Src/Abl pathway, which has been studied in hematologic malignancies. Preclinical data suggests that the addition of bosutinib to a CDK4/6 inhibitor and antiestrogen therapy has the potential to reverse endocrine resistance. This is a phase I, single arm, open-label clinical trial in which we evaluate the combination of palbociclib and fulvestrant with bosutinib in metastatic HR+ breast cancer. Patients with confirmed advanced HR+/HER2- breast cancer who have received no more than three lines of chemotherapy and have progressed on at least one aromatase inhibitor and one CDK4/6 inhibitor will be enrolled. Participants will be given a combination of palbociclib, fulvestrant and bosutinib over 28-day cycles. The primary objective of this study is to assess the safety and tolerability of bosutinib in combination with palbociclib and fulvestrant in the study population. Secondary objectives are to 1) determine the anti-tumor effect of this therapeutic combination by assessing overall response rate (ORR) and clinical benefit rate (CBR) after 6 months of treatment, 2) to determine the clinical pharmacology parameters of bosutinib in this regimen, and 3) to build a tissue repository at Georgetown Lombardi Comprehensive Cancer Center for further translational study.

Screening tumor specificity targeted by arnicolide D, the active compound of Centipeda minima and molecular mechanism underlying by integrative pharmacology

ETHNOPHARMACOLOGICAL RELEVANCE

Herb-derived anti-tumor agents, such as paclitaxel and vincristine, exert significant but varied effectivenesses towards different cancer types. Similarly, Centipeda minima (CM) is a well-known traditional Chinese medicine that has been used to treat rhinitis, relieve pain and reduce swelling, and recently found to exert overwhelming anti-tumor effects against breast cancer, colon cancer, and nasopharyngeal carcinoma with different response rates. However, what is the optimizing cancer model that benefits most from CM, and what is the specific target underlying still require more exclusive and profound investigations.

AIMS OF THE STUDY

This study aimed to explore the dominant tumor model and specific target of CM by integrative pharmacology and biological experiments.

MATERIALS AND METHODS

The most predominant and specific cancer types that are sensitive to CM were screened and identified based on a combination network pharmacology and bioinformatics analysis. Compound-target network and protein-protein interaction of CM-related cancer targets were carried out to determine the most abundant active compound. Simultaneously, the priority target responsible for CM-related anti-tumor efficacy was further validated by molecular docking and in vitro experiments.

RESULTS

In total, approximately 42% (8/19) of the targets were enriched in prostate cancer (p = 1.25E-09), suggesting prostate cancer would be the most sensitive tumor response to CM-related efficacy. Furthermore, we found that arnicolide D (ARD), the most abundant and representative active compound of CM, could directly bind to Src with binding energy of -7.3 kcal/mol, implying Src would be the priority target responsible for CM-related anti-tumor efficacy. Meanwhile, the results were further validated by solvent-induced protein precipitation (SIP) assay. In addition, PCR and WB results also revealed that either CM or ARD could not influence the gene expression of Src, while significantly decreased its protein expression instead, which further suggested that ARD might markedly shortene the Src protein half-life to promote Src protein degradation, thereby achieving significant anti-prostate cancer efficacy.

CONCLUSION

Our findings not only suggest CM as a promising Src-targeting candidate for prostate cancer treatment, but also bring up a strategy for understanding the personalization of herbal medicines by using integrative pharmacology.

SRC kinase-mediated signaling pathways and targeted therapies in breast cancer

Breast cancer (BC) has been ranked the most common malignant tumor throughout the world and is also a leading cause of cancer-related deaths among women. SRC family kinases (SFKs) belong to the non-receptor tyrosine kinase (nRTK) family, which has eleven members sharing similar structure and function. Among them, SRC is the first identified proto-oncogene in mammalian cells. Oncogenic overexpression or activation of SRC has been revealed to play essential roles in multiple events of BC progression, including tumor initiation, growth, metastasis, drug resistance and stemness regulations. In this review, we will first give an overview of SRC kinase and SRC-relevant functions in various subtypes of BC and then systematically summarize SRC-mediated signaling transductions, with particular emphasis on SRC-mediated substrate phosphorylation in BC. Furthermore, we will discuss the progress of SRC-based targeted therapies in BC and the potential future direction.

Endocrine Resistance in Breast Cancer: The Role of Estrogen Receptor Stability

Therapy of hormone receptor positive breast cancer (BCa) generally targets estrogen receptor (ER) function and signaling by reducing estrogen production or by blocking its interaction with the ER. Despite good long-term responses, resistance to treatment remains a significant issue, with approximately 40% of BCa patients developing resistance to ET. Mutations in the gene encoding ERα, ESR1, have been identified in BCa patients and are implicated as drivers of resistance and disease recurrence. Understanding the molecular consequences of these mutations on ER protein levels and its activity, which is tightly regulated, is vital. ER activity is in part controlled via its short protein half-life and therefore changes to its stability, either through mutations or alterations in pathways involved in protein stability, may play a role in therapy resistance. Understanding these connections and how ESR1 alterations could affect protein stability may identify novel biomarkers of resistance. This review explores the current reported data regarding posttranslational modifications (PTMs) of the ER and the potential impact of known resistance associated ESR1 mutations on ER regulation by affecting these PTMs in the context of ET resistance.

Src Family Kinases as Therapeutic Targets in Advanced Solid Tumors: What We Have Learned so Far

Src is the prototypal member of Src Family tyrosine Kinases (SFKs), a large non-receptor kinase class that controls multiple signaling pathways in animal cells. SFKs activation is necessary for the mitogenic signal from many growth factors, but also for the acquisition of migratory and invasive phenotype. Indeed, oncogenic activation of SFKs has been demonstrated to play an important role in solid cancers; promoting tumor growth and formation of distant metastases. Several drugs targeting SFKs have been developed and tested in preclinical models and many of them have successfully reached clinical use in hematologic cancers. Although in solid tumors SFKs inhibitors have consistently confirmed their ability in blocking cancer cell progression in several experimental models; their utilization in clinical trials has unveiled unexpected complications against an effective utilization in patients. In this review, we summarize basic molecular mechanisms involving SFKs in cancer spreading and metastasization; and discuss preclinical and clinical data highlighting the main challenges for their future application as therapeutic targets in solid cancer progression

Randomized phase-II evaluation of letrozole plus dasatinib in hormone receptor positive metastatic breast cancer patients

The non-receptor tyrosine kinase Src activation plays a role in the malignant progression of breast cancer, including development of endocrine therapy resistance and survival of bone metastases. This study investigated whether adding Src kinase inhibitor dasatinib to aromatase inhibitor (AI) therapy improved outcomes in estrogen receptor (ER)-positive, HER2-negative metastatic breast cancer (MBC). Postmenopausal patients with ER-positive, HER2-negative MBC (0-1 prior chemotherapies and no prior AI for MBC) were eligible for this non-comparative, parallel group, phase-II study. Patients were randomized to letrozole (2.5 mg/day PO) alone or with dasatinib (100 mg/day PO). Patients with disease progression on letrozole alone could crossover to dasatinib plus continued letrozole. The primary endpoint was clinical-benefit-rate (CBR; complete response + partial response + stable disease ≥6 months). A total of 120 patients were randomized. The CBR of 71% (95% CI 58-83%) was observed with letrozole + dasatinib versus the projected CBR of the combination of 56%. The CBR of 66% (95% CI 52-77%) with letrozole alone also exceeded the projected CBR of 39% with letrozole alone. The CBR was 23% in the crossover arm of letrozole plus dasatinib in patients progressing on letrozole alone. Median progression-free survival with the combination was 20.1 months and 9.9 months with letrozole alone. Letrozole plus dasatinib was well tolerated, although 26% of patients required dasatinib dose reductions. In this non-comparative phase-II trial, the CBR of 71% and the median PFS of 20.1 months with letrozole + dasatinib are encouraging and suggest that dasatinib may inhibit the emergence of acquired resistance to AI therapy.

Myeloid cell leukemia 1 (MCL-1), an unexpected modulator of protein kinase signaling during invasion

Myeloid cell leukemia-1 (MCL-1), closely related to B-cell lymphoma 2 (BCL-2), has a well-established role in cell survival and has emerged as an important target for cancer therapeutics. We have demonstrated that inhibiting MCL-1 is efficacious in suppressing tumour progression in pre-clinical models of breast cancer and revealed that in addition to its role in cell survival, MCL-1 modulated cellular invasion. Utilizing a MCL-1-specific genetic antagonist, we found two possible mechanisms; firstly MCL-1 directly binds to and alters the phosphorylation of the cytoskeletal remodeling protein, Cofilin, a protein important for cytoskeletal remodeling during invasion, and secondly MCL-1 modulates the levels SRC family kinases (SFKs) and their targets. These data provide evidence that MCL-1 activities are not limited to endpoints of extracellular and intracellular signaling culminating in cell survival as previously thought, but can directly modulate the output of SRC family kinases signaling during cellular invasion. Here we review the pleotropic roles of MCL-1 and discuss the implications of this newly discovered effect on protein kinase signaling for the development of cancer therapeutics.

Hematopoietic cell kinase (HCK) as a therapeutic target in immune and cancer cells

The hematopoietic cell kinase (HCK) is a member of the SRC family of cytoplasmic tyrosine kinases (SFKs), and is expressed in cells of the myeloid and B-lymphocyte cell lineages. Excessive HCK activation is associated with several types of leukemia and enhances cell proliferation and survival by physical association with oncogenic fusion proteins, and with functional interactions with receptor tyrosine kinases. Elevated HCK activity is also observed in many solid malignancies, including breast and colon cancer, and correlates with decreased patient survival rates. HCK enhances the secretion of growth factors and pro-inflammatory cytokines from myeloid cells, and promotes macrophage polarization towards a wound healing and tumor-promoting alternatively activated phenotype. Within tumor associated macrophages, HCK stimulates the formation of podosomes that facilitate extracellular matrix degradation, which enhance immune and epithelial cell invasion. By virtue of functional cooperation between HCK and bona fide oncogenic tyrosine kinases, excessive HCK activation can also reduce drug efficacy and contribute to chemo-resistance, while genetic ablation of HCK results in minimal physiological consequences in healthy mice. Given its known crystal structure, HCK therefore provides an attractive therapeutic target to both, directly inhibit the growth of cancer cells, and indirectly curb the source of tumor-promoting changes in the tumor microenvironment.