p27kip1 is a cyclin-dependent kinase (CDK) inhibitor (CKI) and mainly acts as a negative regulator of cell proliferation. Through distinct domains, p27kip1 has also been involved in the control of other cellular processes, including migration, differentiation and cytoskeleton dynamics. p27kip1 protein is frequently inactivated in human cancer and its subcellular localization (cytoplasmic versus nuclear) can be prognostic in some tumors, such as breast, colon, prostate, lung, esophageal, and gastric cancers (Ananthanarayanan et al. 2011; Wen et al. 2012). With the advent of next generation sequencing approaches, p27kip1 has been identified as one of the 18 most significantly mutated genes in luminal breast cancer (Stephens et al. 2012; Ellis et al. 2012; Belletti, Baldassarre et al. 2012). Furthermore, the analysis of copy number variation showed that a fraction of luminal breast cancer also displayed loss or gain of CDKN1B gene, encoding for p27kip1 (Viotto, Russo et al. 2021), reinforcing the idea that p27kip1 may be critical for luminal breast cancer onset and/or progresssion. Interestingly, many of the identified somatic mutations are located in the C-terminal domain, leading to protein loss or truncated protein formation. Therefore, to elucidate the role of p27kip1 in luminal breast cancer, we first used a gene-editing approach in a luminal breast cancer cell line and investigated the effects induced by loss of p27kip1 and by expression of two different truncated mutants, K134fs and T171*, losing p27kip1 C-terminal domain. Our results clearly showed that these mutants, failed to rescue most of the phenotypes induced by CDKN1B gene knock-out, indicating that the functions retained by this portion are critical for its role as an oncosuppressor, both in vitro (Viotto, Russo et al. 2021) and in vivo. Moreover, we observed that lack of p27kip1 or expression of its mutant forms increased the resistance to the treatment with Palbociclib, currently one of the most common therapeutic strategies for luminal breast cancer patients. Finally, to evaluate whether p27kip1 could also represent a driver genetic lesion during the process of transformation, we have also shown the involvement of p27kip1 in the process of cell transformation and tumor initiation. Generating p27kip1 knock-out clones in normal human mammary luminal epithelial cell line, we have noticed its ability to significantly increase the proliferation cell rate of these normal cells. Interestingly, the only deficiency of p27kip1 seems to lead the cells toward a stem phenotype and also therapy resistance, highlight the important role of p27kip1 also in the early steps of mammary cancer formation.

Implicazione di p27 kip1 nell'esordio e nella progressione del carcinoma mammario luminale

RUSSO, FRANCESCA
2022

Abstract

p27kip1 is a cyclin-dependent kinase (CDK) inhibitor (CKI) and mainly acts as a negative regulator of cell proliferation. Through distinct domains, p27kip1 has also been involved in the control of other cellular processes, including migration, differentiation and cytoskeleton dynamics. p27kip1 protein is frequently inactivated in human cancer and its subcellular localization (cytoplasmic versus nuclear) can be prognostic in some tumors, such as breast, colon, prostate, lung, esophageal, and gastric cancers (Ananthanarayanan et al. 2011; Wen et al. 2012). With the advent of next generation sequencing approaches, p27kip1 has been identified as one of the 18 most significantly mutated genes in luminal breast cancer (Stephens et al. 2012; Ellis et al. 2012; Belletti, Baldassarre et al. 2012). Furthermore, the analysis of copy number variation showed that a fraction of luminal breast cancer also displayed loss or gain of CDKN1B gene, encoding for p27kip1 (Viotto, Russo et al. 2021), reinforcing the idea that p27kip1 may be critical for luminal breast cancer onset and/or progresssion. Interestingly, many of the identified somatic mutations are located in the C-terminal domain, leading to protein loss or truncated protein formation. Therefore, to elucidate the role of p27kip1 in luminal breast cancer, we first used a gene-editing approach in a luminal breast cancer cell line and investigated the effects induced by loss of p27kip1 and by expression of two different truncated mutants, K134fs and T171*, losing p27kip1 C-terminal domain. Our results clearly showed that these mutants, failed to rescue most of the phenotypes induced by CDKN1B gene knock-out, indicating that the functions retained by this portion are critical for its role as an oncosuppressor, both in vitro (Viotto, Russo et al. 2021) and in vivo. Moreover, we observed that lack of p27kip1 or expression of its mutant forms increased the resistance to the treatment with Palbociclib, currently one of the most common therapeutic strategies for luminal breast cancer patients. Finally, to evaluate whether p27kip1 could also represent a driver genetic lesion during the process of transformation, we have also shown the involvement of p27kip1 in the process of cell transformation and tumor initiation. Generating p27kip1 knock-out clones in normal human mammary luminal epithelial cell line, we have noticed its ability to significantly increase the proliferation cell rate of these normal cells. Interestingly, the only deficiency of p27kip1 seems to lead the cells toward a stem phenotype and also therapy resistance, highlight the important role of p27kip1 also in the early steps of mammary cancer formation.
34
2020/2021
Settore MED/06 - Oncologia Medica
Università degli Studi di Trieste
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11368/3030940
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