Retinoic acid receptor activation reprograms senescence response and enhances anti-tumor activity of natural killer cells

Cellular senescence can exert dual effects in tumors, either suppressing or promoting tumor progression. The senescence-associated secretory phenotype (SASP), released by senescent cells, plays a crucial role in this dichotomy. Consequently, the clinical challenge lies in developing therapies that safely enhance senescence in cancer, favoring tumor-suppressive SASP factors over tumor-promoting ones. Here, we identify the retinoic-acid-receptor (RAR) agonist adapalene as an effective pro-senescence compound in prostate cancer (PCa). Reactivation of RARs triggers a robust senescence response and a tumor-suppressive SASP. In preclinical mouse models of PCa, the combination of adapalene and docetaxel promotes a tumor-suppressive SASP that enhances natural killer (NK) cell-mediated tumor clearance more effectively than either agent alone. This approach increases the efficacy of the allogenic infusion of human NK cells in mice injected with human PCa cells, suggesting an alternative therapeutic strategy to stimulate the anti-tumor immune response in "immunologically cold" tumors.

The potential role of the microbiota in prostate cancer pathogenesis and treatment

The human body hosts a complex and dynamic population of trillions of microorganisms - the microbiota - which influences the body in homeostasis and disease, including cancer. Several epidemiological studies have associated specific urinary and gut microbial species with increased risk of prostate cancer; however, causal mechanistic data remain elusive. Studies have associated bacterial generation of genotoxins with the occurrence of TMPRSS2-ERG gene fusions, a common, early oncogenic event during prostate carcinogenesis. A subsequent study demonstrated the role of the gut microbiota in prostate cancer endocrine resistance, which occurs, at least partially, through the generation of androgenic steroids fuelling oncogenic signalling via the androgen receptor. These studies present mechanistic evidence of how the host microbiota might be implicated in prostate carcinogenesis and tumour progression. Importantly, these findings also reveal potential avenues for the detection and treatment of prostate cancer through the profiling and modulation of the host microbiota. The latter could involve approaches such as the use of faecal microbiota transplantation, prebiotics, probiotics, postbiotics or antibiotics, which can be used independently or combined with existing treatments to reverse therapeutic resistance and improve clinical outcomes in patients with prostate cancer.

Commensal bacteria promote endocrine resistance in prostate cancer through androgen biosynthesis

[Figure: see text].

Structural and Electrophysiological Changes in a Model of Cardiotoxicity Induced by Anthracycline Combined With Trastuzumab

Background

Combined treatment with anthracyclines (e.g., doxorubicin; Dox) and trastuzumab (Trz), a humanized anti-human epidermal growth factor receptor 2 (HER2; ErbB2) antibody, in patients with HER2-positive cancer is limited by cardiotoxicity, as manifested by contractile dysfunction and arrhythmia. The respective roles of the two agents in the cardiotoxicity of the combined therapy are incompletely understood.

Objective

To assess cardiac performance, T-tubule organization, electrophysiological changes and intracellular Ca²⁺ handling in cardiac myocytes (CMs) using an in vivo rat model of Dox/Trz-related cardiotoxicity.

Methods and Results

Adult rats received 6 doses of either Dox or Trz, or the two agents sequentially. Dox-mediated left ventricular (LV) dysfunction was aggravated by Trz administration. Dox treatment, but not Trz, induced T-tubule disarray. Moreover, Dox, but not Trz monotherapy, induced prolonged action potential duration (APD), increased incidence of delayed afterdepolarizations (DADs) and beat-to-beat variability of repolarization (BVR), and slower Ca²⁺ transient decay. Although APD, DADs, BVR and Ca²⁺ transient decay recovered over time after the cessation of Dox treatment, subsequent Trz administration exacerbated these abnormalities. Trz, but not Dox, reduced Ca²⁺ transient amplitude and SR Ca²⁺ content, although only Dox treatment was associated with SERCA downregulation. Finally, Dox treatment increased Ca²⁺ spark frequency, resting Ca²⁺ waves, sarcoplasmic reticulum (SR) Ca²⁺ leak, and long-lasting Ca²⁺ release events (so-called Ca²⁺ “embers”), partially reproduced by Trz treatment.

Conclusion

These results suggest that in vivo Dox but not Trz administration causes T-tubule disarray and pronounced changes in electrical activity of CMs. While adaptive changes may account for normal AP shape and reduced DADs late after Dox administration, subsequent Trz administration interferes with such adaptive changes. Intracellular Ca²⁺ handling was differently affected by Dox and Trz treatment, leading to SR instability in both cases. These findings illustrate the specific roles of Dox and Trz, and their interactions in cardiotoxicity and arrhythmogenicity.

Senescence Reprogramming by TIMP1 Deficiency Promotes Prostate Cancer Metastasis

Metastases account for most cancer-related deaths, yet the mechanisms underlying metastatic spread remain poorly understood. Recent evidence demonstrates that senescent cells, while initially restricting tumorigenesis, can induce tumor progression. Here, we identify the metalloproteinase inhibitor TIMP1 as a molecular switch that determines the effects of senescence in prostate cancer. Senescence driven either by PTEN deficiency or chemotherapy limits the progression of prostate cancer in mice. TIMP1 deletion allows senescence to promote metastasis, and elimination of senescent cells with a senolytic BCL-2 inhibitor impairs metastasis. Mechanistically, TIMP1 loss reprograms the senescence-associated secretory phenotype (SASP) of senescent tumor cells through activation of matrix metalloproteinases (MMPs). Loss of PTEN and TIMP1 in prostate cancer is frequent and correlates with resistance to docetaxel and worst clinical outcomes in patients treated in an adjuvant setting. Altogether, these findings provide insights into the dual roles of tumor-associated senescence and can potentially impact the treatment of prostate cancer.

P1622Cancer drugs induce functional and structural impairment in adult cardiomyocytes

Introduction

The addition of anti-human epidermal growth factor receptor 2 (HER2; ErbB2) monoclonal antibody Trastuzumab (TRZ) to Doxorubicin (DOXO) chemotherapy is associated with a synergistic increase in cardiac toxicity. While previous studies have addressed the toxicity of both agents on isolated cardiomyocytes (CMs), little is known regarding this process in vivo, especially with respect to electrophysiological changes.

Purpose

To investigate electrical and structural changes in LV and RV CMs using an in vivo rat model of DOXO/TRZ cardiotoxicity.

Methods

Rats received 6 IP injections of either DOXO or TRZ over a 2-week period, or 6 doses of DOXO followed by 6 doses of TRZ (COMBO), or saline as a control. In-vivo echocardiography was performed. Electrical activity and Ca2+ handling were assessed in LV and RV CMs from rat hearts. Single cell patch-clamp and field stimulation experiments were performed. Spontaneous sarcoplasmic reticulum Ca2+ release events (Ca2+ sparks) were recorded at x100 magnification in line-scan mode (sampling rate 0.7 kHz) from 2 μM Fluo4-AM loaded CMs. To assess T-tubular disarray, CMs were incubated with di-3-ANEPPDHQ and periodic component was quantified by Fast Fourier Transform (FFT) analysis of confocal microscopy images.

Results

DOXO, and to a greater extent COMBO treatment was associated with significant increases in both LV end-systolic and end-diastolic volumes, and decreases in LVEF and fractional shortening. By contrast, TRZ alone merely increased LV end-systolic volume. Electrophysiological studies showed increases in action potential duration (APD), beat-to-beat variability of repolarization (BVR), delayed after depolarizations (DADs), and Ca2+-sparks in both DOXO and COMBO groups. Stimulated intracellular Ca2+ transients (1,2 and 4 Hz) showed significant changes with respect to time to peak, tau decay, amplitude, and fractional release in the DOXO group. These changes were associated with a significant downregulation of sarco/endoplasmic reticulum Ca2+ ATPase pump (SERCA) expression. From a structural viewpoint, these changes were associated with T-tubular disarray in the DOXO and COMBO groups.

Conclusions

DOXO, and to a greater extent COMBO treatment (but not TRZ alone) cause LV dysfunction in vivo. Moreover, both DOXO and COMBO treatments, but not TRZ alone, induce electrophysiological abnormalities and both structural and functional changes in the sarcoplasmic reticulum. These findings provide novel insights into the cellular mechanisms of CM dysfunction and arrhythmias associated with combined DOXO/TRZ therapy.

Acknowledgement/Funding

Swiss League against Cancer