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

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.

Proteomic time course of breast cancer cells highlights enhanced sensitivity to Stat3 and Src inhibitors prior to endocrine resistance development

To prevent the development of endocrine-resistant breast cancer, additional targeted therapies are increasingly being trialled in combination with endocrine therapy. The molecular mechanisms facilitating cancer cell survival during endocrine treatment remain unknown but could help direct selection of additional targeted therapies. We present a novel proteomic timecourse dataset, profiling potential drug targets in a population of MCF7 cells during 1 year of tamoxifen treatment. Reverse phase protein arrays profiled >70 proteins across 30 timepoints. A biphasic response to tamoxifen was evident, which coincided with changes in growth rate. Tamoxifen strongly impeded cell growth for the first 160 days, followed by gradual growth recovery and eventual resistance development. The growth-impeded phase was distinguished by the phosphorylation of Stat3 (y705) and Src (y527). Tumour tissue from patients treated with neo-adjuvant endocrine therapy (<4 months) also displayed increased Stat3 and Src signalling. Inhibitors of Stat3 (napabucasin) and Src (dasatinib), were effective at killing tamoxifen-treated MCF7 and T47D cells. Sensitivity to both drugs was significantly enhanced once tamoxifen had induced the growth-impeded phase. This novel proteomic resource identifies key mechanisms enabling cell survival during tamoxifen treatment. It provides valuable insight into potential drug combinations and timing that may prevent the development of endocrine resistance.

Endocrine Therapy-Based Strategies for Metastatic Breast Cancer with Different Endocrine Sensitivity Statuses: A Systematic Review and Network Meta-Analysis

BACKGROUND

Novel endocrine therapies (ETs) and targeted therapeutic regimens have been developed to dramatically improve the outcome of hormone receptor-positive (HR+)/HER2-negative (HER2-) metastatic breast cancer (mBC).

METHODS

We performed a systematic search with a predefined search strategy in PubMed, Embase and Cochrane CENTRAL databases to perform a network meta-analysis and evaluate the relative efficacies of ET-based treatment regimens in HR+/HER2- mBC patients with different endocrine sensitivity statuses. The study was registered in the PROSPERO database (CRD42021235570).

RESULTS

A total of 47 trials (20,267 patients) were included. Analysis of progression-free survival (PFS) in endocrine therapy-sensitive (ETS) patients revealed cyclin-dependent kinases 4/6 inhibitors (CDK4/6i) + fulvestrant 500 mg (Ful 500) (random effect (RE): hazard ratio (HR), 0.46; 95% credibility interval (CrI), 0.27-0.78; surface under the cumulative ranking curve (SUCRA), 0.93; fixed effect (FE): HR, 0.48; 95% CrI, 0.40-0.58; SUCRA, 0.99) to be the best therapy followed by CDK4/6i + aromatase inhibitors (AIs) (RE: HR, 0.53; 95% CrI, 0.40-0.72; SUCRA, 0.86; FE: HR, 0.54; 95% CrI, 0.48-0.61; SUCRA, 0.91). Chemotherapy followed by CDK4/6i + Ful 500 appears to be the most effective option for the endocrine therapy-resistant (ETR) group. Analysis of overall survival revealed CDK4/6i + Ful 500 (SUCRA: 0.99) and AKTi + Ful 500 (SUCRA: 0.87) to be the first-rank regimen for the ETS group and ETR groups, respectively.

CONCLUSION

Our comprehensive analysis suggests that CDK4/6i combined with ETs may be the best treatment option in terms of PFS for ETS patients and chemotherapy for ETR patients with HR+/HER2- mBC. Different endocrine sensitivity statuses required various optimal treatment strategies, which may provide guidance for clinical practice.

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.

YES1 as a Therapeutic Target for HER2-Positive Breast Cancer after Trastuzumab and Trastuzumab-Emtansine (T-DM1) Resistance Development

Trastuzumab-emtansine (T-DM1) is a therapeutic agent molecularly targeting human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC), and it is especially effective for MBC with resistance to trastuzumab. Although several reports have described T-DM1 resistance, few have examined the mechanism underlying T-DM1 resistance after the development of acquired resistance to trastuzumab. We previously reported that YES1, a member of the Src family, plays an important role in acquired resistance to trastuzumab in HER2-amplified breast cancer cells. We newly established a trastuzumab/T-DM1-dual-resistant cell line and analyzed the resistance mechanisms in this cell line. At first, the T-DM1 effectively inhibited the YES1-amplified trastuzumab-resistant cell line, but resistance to T-DM1 gradually developed. YES1 amplification was further enhanced after acquired resistance to T-DM1 became apparent, and the knockdown of the YES1 or the administration of the Src inhibitor dasatinib restored sensitivity to T-DM1. Our results indicate that YES1 is also strongly associated with T-DM1 resistance after the development of acquired resistance to trastuzumab, and the continuous inhibition of YES1 is important for overcoming resistance to T-DM1.

Comparison of Endocrine Therapies in Hormone Receptor-Positive and Human Epidermal Growth Factor Receptor 2-Negative Locally Advanced or Metastatic Breast Cancer: A Network Meta-Analysis

We aimed to explore what kind of endocrine treatments are optimal for hormone receptor-positive and human epidermal growth factor receptor 2-negative locally advanced or metastatic breast cancer in some specific clinical situations. We searched randomized controlled trials in Embase, Medline, the Cochrane library, and PubMed from inception to April 1, 2020 and performed a network meta-analysis based on a Bayesian fixed-effects model. Progression-free survival (PFS) with hazard ratios and corresponding 95% confidence interval was defined as the primary endpoint, while overall survival (OS), objective response rate (ORR), clinical benefit rate and serious adverse events were used as secondary endpoints. A total of 35 studies involving 12,285 patients and 24 treatment options were included. In general, most co-treatment options prolonged PFS compared to single-agent therapy, of which aromatase inhibitor (AI) plus everolimus and fulvestrant plus palbociclib were probably the most effective agents, and the latter had the best safety record. However, despite the superior efficacy of fulvestrant plus capecitabine for PFS and OS, palpable toxic effects have been demonstrated for this treatment, so its application must be scrupulously considered. The results of subgroup analysis indicated that fulvestrant combined with palbociclib improved prognosis for phosphatidylinositol 3-kinase (PI3K)-mutated patients, PI3K-unmutated patients, patients with endocrine therapy resistance, and visceral metastatic patients, while no obvious improvement was detected in OS. Moreover, the efficacy of fulvestrant plus cyclin-dependent kinase 4/6 (CDK4/6) inhibitors was slightly better than that of AI plus CDK4/6 inhibitors, while AI plus everolimus was more efficacious than fulvestrant combined with everolimus in terms of PFS, OS, and ORR. In conclusion, our results provide moderate evidence that fulvestrant plus palbociclib and AI plus everolimus were the most effective treatments, while the efficacy and safety of fulvestrant plus palbociclib was obviously superior in some specific clinical situations.

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.

Reprogramming of Mesothelial-Mesenchymal Transition in Chronic Peritoneal Diseases by Estrogen Receptor Modulation and TGF-β1 Inhibition

In chronic peritoneal diseases, mesothelial-mesenchymal transition is determined by cues from the extracellular environment rather than just the cellular genome. The transformation of peritoneal mesothelial cells and other host cells into myofibroblasts is mediated by cell membrane receptors, Transforming Growth Factor β1 (TGF-β1), Src and Hypoxia-inducible factor (HIF). This article provides a narrative review of the reprogramming of mesothelial mesenchymal transition in chronic peritoneal diseases, drawing on the similarities in pathophysiology between encapsulating peritoneal sclerosis and peritoneal metastasis, with a particular focus on TGF-β1 signaling and estrogen receptor modulators. Estrogen receptors act at the cell membrane/cytosol as tyrosine kinases that can phosphorylate Src, in a similar way to other receptor tyrosine kinases; or can activate the estrogen response element via nuclear translocation. Tamoxifen can modulate estrogen membrane receptors, and has been shown to be a potent inhibitor of mesothelial-mesenchymal transition (MMT), peritoneal mesothelial cell migration, stromal fibrosis, and neoangiogenesis in the treatment of encapsulating peritoneal sclerosis, with a known side effect and safety profile. The ability of tamoxifen to inhibit the transduction pathways of TGF-β1 and HIF and achieve a quiescent peritoneal stroma makes it a potential candidate for use in cancer treatments. This is relevant to tumors that spread to the peritoneum, particularly those with mesenchymal phenotypes, such as colorectal CMS4 and MSS/EMT gastric cancers, and pancreatic cancer with its desmoplastic stroma. Morphological changes observed during mesothelial mesenchymal transition can be treated with estrogen receptor modulation and TGF-β1 inhibition, which may enable the regression of encapsulating peritoneal sclerosis and peritoneal metastasis.