Combination of palbociclib with navitoclax based-therapies enhances in vivo antitumoral activity in triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is a very aggressive subtype of breast cancer with a poor prognosis and limited effective therapeutic options. Induction of senescence, arrest of cell proliferation, has been explored as an effective method to limit tumor progression in metastatic breast cancer. However, relapses occur in some patients, possibly as a result of the accumulation of senescent tumor cells in the body after treatment, which promote metastasis. In this study, we explored the combination of senescence induction and the subsequent removal of senescent cells (senolysis) as an alternative approach to improve outcomes in TNBC patients. We demonstrate that a combination treatment, using the senescence-inducer palbociclib and the senolytic agent navitoclax, delays tumor growth and reduces metastases in a mouse xenograft model of aggressive human TNBC (hTNBC). Furthermore, considering the off-target effects and toxicity derived from the use of navitoclax, we propose a strategy aimed at minimizing the associated side effects. We use a galacto-conjugated navitoclax (nav-Gal) as a senolytic prodrug that can preferentially be activated by ß-galactosidase overexpressed in senescent cells. Concomitant treatment with palbociclib and nav-Gal in vivo results in the eradication of senescent hTNBC cells with consequent reduction of tumor growth, while reducing the cytotoxicity of navitoclax. Taken together, our results support the efficacy of combination therapy of senescence-induction with senolysis for hTNBC, as well as the development of a targeted approach as an effective and safer therapeutic opportunity.

A Two-Photon Probe Based on Naphthalimide-Styrene Fluorophore for the In Vivo Tracking of Cellular Senescence.

Cellular senescence is a state of stable cell cycle arrest that can negatively affect the regenerative capacities of tissues and can contribute to inflammation and the progression of various aging-related diseases. Advances in the in vivo detection of cellular senescence are still crucial to monitor the action of senolytic drugs and to assess the early onset or accumulation of senescent cells. Here, we describe a naphthalimide-styrene-based probe (HeckGal) for the detection of cellular senescence both in vitro and in vivo. HeckGal is hydrolyzed by the increased lysosomal ß-galactosidase activity of senescent cells, resulting in fluorescence emission. The probe was validated in vitro using normal human fibroblasts and various cancer cell lines undergoing senescence induced by different stress stimuli. Remarkably, HeckGal was also validated in vivo in an orthotopic breast cancer mouse model treated with senescence-inducing chemotherapy and in a renal fibrosis mouse model. In all cases, HeckGal allowed the unambiguous detection of senescence in vitro as well as in tissues and tumors in vivo. This work is expected to provide a potential technology for senescence detection in aged or damaged tissues.

Preclinical antitumor efficacy of senescence-inducing chemotherapy combined with a nanoSenolytic.

The induction of senescence produces a stable cell cycle arrest in cancer cells, thereby inhibiting tumor growth; however, the incomplete immune cell-mediated clearance of senescent cells may favor tumor relapse, limiting the long-term anti-tumorigenic effect of such drugs. A combination of senescence induction and the elimination of senescent cells may, therefore, represent an efficient means to inhibit tumor relapse. In this study, we explored the antitumor efficacy of a combinatory senogenic and targeted senolytic therapy in an immunocompetent orthotopic mouse model of the aggressive triple negative breast cancer subtype. Following palbociclib-induced senogenesis and senolysis by treatment with nano-encapsulated senolytic agent navitoclax, we observed inhibited tumor growth, reduced metastases, and a reduction in the systemic toxicity of navitoclax. We believe that this combination treatment approach may have relevance to other senescence-inducing chemotherapeutic drugs and additional tumor types. SIGNIFICANCE: While the application of senescence inducers represents a successful treatment strategy in breast cancer patients, some patients still relapse, perhaps due to the subsequent accumulation of senescent cells in the body that can promote tumor recurrence. We now demonstrate that a combination treatment of a senescence inducer and a senolytic nanoparticle selectively eliminates senescent cells, delays tumor growth, and reduces metastases in a mouse model of aggressive breast cancer. Collectively, our results support targeted senolysis as a new therapeutic opportunity to improve outcomes in breast cancer patients.

Real-Time In†Vivo Detection of Cellular Senescence through the Controlled Release of the NIR Fluorescent Dye Nile Blue.

In vivo detection of cellular senescence is accomplished by using mesoporous silica nanoparticles loaded with the NIR-FDA approved Nile blue (NB) dye and capped with a galactohexasaccharide (S3). NB emission at 672 nm is highly quenched inside S3, yet a remarkable emission enhancement is observed upon cap hydrolysis in the presence of ß-galactosidase and dye release. The efficacy of the probe to detect cellular senescence is tested in vitro in melanoma SK-Mel-103 and breast cancer 4T1 cells and in vivo in palbociclib-treated BALB/cByJ mice bearing breast cancer tumor.

A versatile drug delivery system targeting senescent cells.

Senescent cells accumulate in multiple aging-associated diseases, and eliminating these cells has recently emerged as a promising therapeutic approach. Here, we take advantage of the high lysosomal ß-galactosidase activity of senescent cells to design a drug delivery system based on the encapsulation of drugs with galacto-oligosaccharides. We show that gal-encapsulated fluorophores are preferentially released within senescent cells in mice. In a model of chemotherapy-induced senescence, gal-encapsulated cytotoxic drugs target senescent tumor cells and improve tumor xenograft regression in combination with palbociclib. Moreover, in a model of pulmonary fibrosis in mice, gal-encapsulated cytotoxics target senescent cells, reducing collagen deposition and restoring pulmonary function. Finally, gal-encapsulation reduces the toxic side effects of the cytotoxic drugs. Drug delivery into senescent cells opens new diagnostic and therapeutic applications for senescence-associated disorders.

An OFF-ON Two-Photon Fluorescent Probe for Tracking Cell Senescence in Vivo.

A naphthalimide-based two-photon probe (AHGa) for the detection of cell senescence is designed. The probe contains a naphthalimide core, an l-histidine methyl ester linker, and an acetylated galactose bonded to one of the aromatic nitrogen atoms of the l-histidine through a hydrolyzable N-glycosidic bond. Probe AHGa is transformed into AH in senescent cells resulting in an enhanced fluorescent emission intensity. In vivo detection of senescence is validated in mice bearing tumor xenografts treated with senescence-inducing chemotherapy.