A prospective phase II clinical trial identifying the optimal regimen for carboplatin plus standard backbone of anthracycline and taxane-based chemotherapy in triple negative breast cancer

RGCC-mediated PLK1 activity drives breast cancer lung metastasis by phosphorylating AMPKα2 to activate oxidative phosphorylation and fatty acid oxidation

BACKGROUND

More than 90% of the mortality of triple-negative breast cancer (TNBC) patients is attributed to cancer metastasis with organotropism. The lung is a frequent site of TNBC metastasis. However, the precise molecular mechanism for lung-specific metastasis of TNBC is not well understood.

METHODS

RNA sequencing was performed to identify patterns of gene expression associated with lung metastatic behavior using 4T1-LM3, MBA-MB-231-LM3, and their parental cells (4T1-P, MBA-MB-231-P). Expressions of RGCC, called regulator of cell cycle or response gene to complement 32 protein, were detected in TNBC cells and tissues by qRT-PCR, western blotting, and immunohistochemistry. Kinase activity assay was performed to evaluate PLK1 kinase activity. The amount of phosphorylated AMP-activated protein kinase α2 (AMPKα2) was detected by immunoblotting. RGCC-mediated metabolism was determined by UHPLC system. Oxidative phosphorylation was evaluated by JC-1 staining and oxygen consumption rate (OCR) assay. Fatty acid oxidation assay was conducted to measure the status of RGCC-mediated fatty acid oxidation. NADPH and ROS levels were detected by well-established assays. The chemical sensitivity of cells was evaluated by CCK8 assay.

RESULTS

RGCC is aberrantly upregulated in pulmonary metastatic cells. High level of RGCC is significantly related with lung metastasis in comparison with other organ metastases. RGCC can effectively promote kinase activity of PLK1, and the activated PLK1 phosphorylates AMPKα2 to facilitate TNBC lung metastasis. Mechanistically, the RGCC/PLK1/AMPKα2 signal axis increases oxidative phosphorylation of mitochondria to generate more energy, and promotes fatty acid oxidation to produce abundant NADPH. These metabolic changes contribute to sustaining redox homeostasis and preventing excessive accumulation of potentially detrimental ROS in metastatic tumor cells, thereby supporting TNBC cell survival and colonization during metastases. Importantly, targeting RGCC in combination with paclitaxel/carboplatin effectively suppresses pulmonary TNBC lung metastasis in a mouse model.

CONCLUSIONS

RGCC overexpression is significantly associated with lung-specific metastasis of TNBC. RGCC activates AMPKα2 and downstream signaling through RGCC-driven PLK1 activity to facilitate TNBC lung metastasis. The study provides implications for RGCC-driven OXPHOS and fatty acid oxidation as important therapeutic targets for TNBC treatment.

Modeling Doxorubicin-Induced Cardiomyopathy With Fibrotic Myocardial Damage in Wistar Rats

Background

Cardiovascular complications, arising after anthracycline chemotherapy, cause a significant deterioration in the life quality and expectancy of those patients who were previously successfully treated for malignant neoplasms. A number of clinical studies have demonstrated that patients with cardiotoxicity manifested during anthracyclines therapy also have extensive fibrotic changes in the cardiac muscle in the long term. Given the lack of an unambiguous understanding of the mechanisms of fibrotic changes formation under doxorubicin treatment in the myocardium, there is the obvious necessity to create a relevant experimental model of chronic doxorubicin-induced cardiomyopathy with fibrotic myocardial lesions and delayed development of diastolic dysfunction.

Methods

The study was divided into two stages: first stage (creation of acute doxorubicin cardiomyopathy) - 35 male Wistar rats; second stage (creation of chronic doxorubicin cardiomyopathy) - 40 male Wistar rats. The animals were split into eight groups (two control ones and six experimental ones), which determined the doxorubicin dose (first stage: 25, 20.4, 15 mg/kg; second stage: 5, 10, 15 mg/kg, intraperitoneally) and the frequency of injection. Echocardiographic, hematological, histological, and molecular methods were used to confirm the successful modeling of acute and chronic doxorubicin-induced cardiomyopathy with fibrotic lesions.

Results

A model of administration six times every other day with a cumulative dose of doxorubicin 20 mg/kg is suitable for evaluation of acute cardiotoxicity. The 15 mg/kg doxorubicin dose is highly cardiotoxic; what's more, it correlates with progressive deterioration of the clinical condition of the animals after 2 months. The optimal cumulative dose of doxorubicin leads to clinical manifestations confirmed by echocardiographic, histological, molecular changes associated with the development of chronic doxorubicin-induced cardiomyopathy with fibrotic lesions of the left ventricular of the cardiac muscle and ensure long-term survival of animals is 10 mg/kg doxorubicin. A dose of 5 mg/kg of the doxorubicin does not ensure the development of fibrous changes formation.

Conclusion

We assume that cumulative dose of 10 mg/kg with a frequency of administration of six times in 2 days can be used to study the mechanisms of anthracycline cardiomyopathy development.

Stabilization of c-Myc by the atypical cell cycle regulator, Spy1, decreases efficacy of breast cancer treatments

PURPOSE

c-Myc is frequently upregulated in breast cancers, however, targeting c-Myc has proven to be a challenge. Targeting of downstream mediators of c-Myc, such as the 'cyclin-like' cell cycle regulator Spy1, may be a viable therapeutic option in a subset of breast cancer subtypes.

METHODS

Mouse mammary tumor cells isolated from MMTV-Myc mice and human breast cancer cell lines were used to manipulate Spy1 levels followed by tamoxifen or chemotherapeutic treatment with a variety of endpoints. Patient samples from TNBC patients were obtained and constructed into a TMA and stained for c-Myc and Spy1 protein levels.

RESULTS

Over time, MMTV-Myc cells show a decreased response to tamoxifen treatment with increasing levels of Spy1 in the tamoxifen-resistant cells. shRNA against Spy1 re-establishes tamoxifen sensitivity. Spy1 was found to be highly elevated in human TNBC cell and patient samples, correlating to c-Myc protein levels. c-Myc was found to be stabilized by Spy1 and knocking down Spy1 in TNBC cells shows a significant increase in response to chemotherapy treatments.

CONCLUSION

Understanding the interplay between protein expression level and response to treatment is a critical factor in developing novel treatment options for breast cancer patients. These data have shown a connection between Spy1 and c-Myc protein levels in more aggressive breast cancer cells and patient samples. Furthermore, targeting c-Myc has proven difficult, these data suggest targeting Spy1 even when c-Myc is elevated can confer an advantage to current chemotherapies.