The caspase-RB connection in cell death

doi:10.1016/S0962-8924(97)01208-7

Trends in Cell Biology

Volume 8, Issue 3, March 1998, Pages 116-120

https://doi.org/10.1016/S0962-8924(97)01208-7 Get rights and content

Abstract

Execution of the cell-death programme requires the activation of a family of cysteine proteases known as caspases. Specific cellular proteins are cleaved by caspases during apoptosis, including the retinoblastoma tumour-suppressor protein (RB1). A caspase-resistant RB1 can attenuate the death response to tumour necrosis factor alpha. The cleavage of RB1 during cell death, together with the increased cell death during embryonic development of Rb-knockout mice, suggests that RB1 degradation contributes to the activation of the cell-death pathway.

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Cited by (124)

Translating RB1 predictive value in clinical cancer therapy: Are we there yet?
2019, Biochemical Pharmacology
The retinoblastoma RB1 gene has been identified in the 80s as the first tumor suppressor. RB1 loss of function, as well alterations in its pathway, occur in most human cancers and often have prognostic value. RB1 has a key role in restraining cell cycle entry and, along with its family members, regulates a myriad of cellular processes and affects cell response to a variety of stimuli, ultimately determining cell fate. Consistently, RB1 status is a crucial determinant of the cell response to antitumoral therapies, impacting on the outcome of both traditional and modern anti-cancer strategies, including precision medicine approaches, such as kinase inhibitors, and immunotherapy. Despite many efforts however, the predictive value of RB1 status in the clinical practice is still underused, mainly owing to the complexity of RB1 function, to differences depending on the cellular context and on the therapeutic strategies, and, not-lastly, to technical issues. Here, we provide an overview of studies analyzing the role of RB1 in response to conventional cytotoxic and cytostatic therapeutic agents in different cancer types, including hormone dependent ones. We also review RB1 predictive value in the response to the last generation CDK4/6 inhibitors, other kinase inhibitors, and immunotherapy and discuss new emerging non-canonical roles of RB1 that could impact on the response to antitumoral treatments.
Caspases interplay with kinases and phosphatases to determine cell fate
2019, European Journal of Pharmacology
Citation Excerpt :
Several studies have shown that RB is responsible for protecting cells against apoptosis and one of the prerequisites for apoptosis is RB cleavage by caspases. Therefore, cells without RB are more susceptible to apoptosis (Almasan et al., 1995; Phillips et al., 1999; Tan and Wang, 1998). Some reports have described a correlation between decreased intact RB and increased cell death.
Cellular differentiation is one of the critical processes in the life of multicellular organisms. In this phenomenon, a non-specialized cell is converted to a specialized one with its own specific function and morphology. One of the requirements for specialization is silencing of the pathways involved in cell proliferation in parallel with turning on the molecular mechanisms involved in differentiation. Similar to other biological phenomena, the change in cellular state from the proliferative to the differentiated needs molecular switches to persuade the change in response to the internal or external inducers. The quiddity of these molecular switches has not been identified, yet. However, there exists a growing body of evidence showing that the same agents involved in apoptosis have a broad contribution to differentiation progression. To our knowledge, this evidence is still ambiguous because it has raised fundamental questions that require more proof to be answered. The most important questions are: How can two totally different cellular fates act through a similar pathway? What is the separating edge? What forces a cell to choose one of them (death or differentiation)? To address these issues, we will concentrate on three groups of molecules; caspases as the key players of apoptosis, protein kinases, and phosphatases as the major regulators of many cellular and biochemical processes. The evidence reveals a triangle of caspases, kinases, and phosphatases in which their communication leads to the fine-tuning of caspases and consequently they determine cell fate.
A selective cyclin-dependent kinase 4, 6 dual inhibitor, Ribociclib (LEE011) inhibits cell proliferation and induces apoptosis in aggressive thyroid cancer
2018, Cancer Letters
The RB-E2F1 pathway is an important mechanism of cell-cycle control, and deregulation of this pathway is one of the key factors contributing to tumorigenesis. Cyclin-dependent kinases (CDKs) and Cyclin D have been known to increase in aggressive thyroid cancer. However, there has been no study to investigate effects of a selective CDK 4/6 inhibitor, Ribociclib (LEE011), in thyroid cancer. Performing Western blotting, we found that RB phosphorylation and the expression of Cyclin D are significantly higher in papillary thyroid cancer (PTC) cell lines as well as anaplastic thyroid cancer (ATC) cell lines, compared with normal thyroid cell line and follicular thyroid cancer cell line. LEE011 dose-dependently inhibited RB phosphorylation and also decreased the expressions of its target genes such as FOXM1, Cyclin A1, and Myc in ATC. Furthermore, LEE011 induced cell cycle arrest in G0-G1 phase and cell apoptosis, and inhibited cell proliferation in ATC. Consistently, oral administration of LEE011 to ATC xenograft models strongly inhibited tumor growth with decreased expressions of pRB, pAKT and Ki-67, and also significantly increased tumor cell apoptosis. Taken together, our data support the rationale for clinical development of the CDK4/6 inhibitor as a therapy for patients with aggressive thyroid cancer.
Neuronal apoptosis in the striatum of rats treated with 3-nitropropionic acid is not triggered by cell-cycle re-entry
2011, NeuroToxicology
Although terminally differentiated neurons lack the capacity to undergo cell division, they retain the capacity to reactivate the cell cycle. This reactivation, however, has been linked to the degeneration of neurons in many experimental models of neurodegenerative disease and in post-mortem brains of affected patients. Expression of markers of the G1 phase and apoptotic neurons has been detected in the striatal lesion of rats treated with 3-nitropropionic acid (3-NPA). Here we examined whether neuronal apoptosis induced by 3-NPA was mediated by the reactivation of the cell cycle. To this end, we studied whether TUNEL-positive neurons expressed the G1-phase markers cyclin-dependent kinase 4 (CDK4) and cyclin D (CyD). In addition, we also evaluated the neuronal expression of pRb and Ki67 antigens, both of which are involved in the regulation of cell-cycle progression. In 3-NPA-treated rats, CDK4 and CyD were not detected in TUNEL-positive neurons, but they were expressed in neurons in the core of the lesion, which were assumed to be in a more advanced stage of degeneration, since they had weaker NeuN staining and lacked Hoechst staining. In addition, injured neurons in the striatal lesion of 3-NPA-treated rats had lost the constitutive expression of pRb and Ki67 that we had detected in control animals. Taken together, these results indicate that neuronal apoptosis in the striatal lesion of 3-NPA-treated rats was not triggered by cell-cycle re-entry, and we conclude that expression of G1 markers may be considered an aberrant survival response, with no relation to the mechanisms of apoptosis.
Caspase substrates and neurodegenerative diseases
2009, Brain Research Bulletin
Apoptosis is induced by the cleavage of a subset of cellular proteins by proteases of the caspase family. Numerous (hundreds) caspase substrates have been described but only for a few of them is the function of their cleavage by caspases well understood. In this review, apoptosis and caspases will first be introduced. The main focus will then be directed to the caspase substrates, the actual “workers” doing the job of mediating and regulating the apoptotic process. The caspase substrates whose functions upon cleavage have been carefully investigated and those that are potentially involved in neurodegenerative diseases will be discussed in detail.
Stress and IGF-I differentially control cell fate through mammalian target of rapamycin (mTOR) and retinoblastoma protein (pRB)
2008, Journal of Biological Chemistry
Citation Excerpt :
The regulation of pRB function is complex. pRB is inactivated primarily through phosphorylation by cyclin/cdk (cyclin-dependent kinase) complexes or caspase-mediated cleavage (23). Often, growth factors enhance the phosphorylation of nine or more residues on pRB which inactivates its binding to E2F transcription factors, leading to cell cycle transit.
Significant discoveries have recently contributed to our knowledge of intracellular growth factor and nutrient signaling via mTOR (mammalian target of rapamycin). This signaling pathway is essential in cellular metabolism and cell survival by enhancing protein translation through phosphorylation of 4EBP-1 and p70S6K. Growth factors like insulin-like growth factor-I induce mTOR to prevent cell death during cellular stress. Agents targeting mTOR are of major interest as anticancer agents. We show here, using human breast cancer cells, that certain types of stress activate mTOR leading to 4E-BP1 and p70S6K phosphorylation. UV treatment increased phosphorylation of the translation inhibitor eIF2α, suggesting a potential mechanism for UV activation of Akt and mTOR. c-Myc, a survival protein regulated by cap-dependent protein translation, increased with IGF-I treatment, but this response was not inhibited by rapamycin. Additionally, UV treatment potently increased c-Myc degradation, which was reduced by co-treatment with the proteasomal inhibitor, MG-132. Together, these data suggest that protein translation does not strongly mediate cell survival in these models. In contrast, the phosphorylation status of retinoblastoma protein (pRB) was mediated by mTOR through its inhibitory effects on phosphatase activity. This effect was most notable during DNA damage and rapamycin treatment. Hypophosphorylated pRB was susceptible to inactivation by caspase-mediated cleavage, resulting in cell death. Reduction of pRB expression inhibited IGF-I survival effects. Our data support an important role of phosphatases and pRB in IGF-I/mTOR-mediated cell survival. These studies provide new directions in optimizing anticancer efficacy of mTOR inhibitors when used in combination with DNA-damaging agents.

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Trends in Cell Biology

ReviewThe caspase-RB connection in cell death

Abstract

Trends Biochem. Sci.

Cell

J. Biol. Chem.

J. Biol. Chem.

Biochem. Biophys. Res. Commun.

Exp. Cell Res.

Cell

Cell

Curr. Opin. Genet. Dev.

Cell

BioEssays

Science

J. Cell Biol.

Science

J. Biol. Chem.

Oncogene

EMBO J.

Development

Science

Oncogene

Review
The caspase-RB connection in cell death