PTEN Expression In Tumors Research Articles

Pan-cancer genomic analysis shows hemizygous PTEN loss tumors are associated with immune evasion and poor outcome

In tumors, somatic mutations of the PTEN suppressor gene are associated with advanced disease, chemotherapy resistance, and poor survival. PTEN loss of function may occur by inactivating mutation, by deletion, either affecting one copy (hemizygous loss) leading to reduced gene expression or loss of both copies (homozygous) with expression absent. Various murine models have shown that minor reductions in PTEN protein levels strongly influence tumorigenesis. Most PTEN biomarker assays dichotomize PTEN (i.e. presence vs. absence) ignoring the role of one copy loss. We performed a PTEN copy number analysis of 9793 TCGA cases from 30 different tumor types. There were 419 (4.28%) homozygous and 2484 (25.37%) hemizygous PTEN losses. Hemizygous deletions led to reduced PTEN gene expression, accompanied by increased levels of instability and aneuploidy across tumor genomes. Outcome analysis of the pan-cancer cohort showed that losing one copy of PTEN reduced survival to comparable levels as complete loss, and was associated with transcriptomic changes controlling immune response and the tumor microenvironment. Immune cell abundances were significantly altered for PTEN loss, with changes in head and neck, cervix, stomach, prostate, brain, and colon more evident in hemizygous loss tumors. These data suggest that reduced expression of PTEN in tumors with hemizygous loss leads to tumor progression and influences anticancer immune response pathways.

Exploiting Chromosomal Instability of PTEN-Deficient Triple-Negative Breast Cancer Cell Lines for the Sensitization against PARP1 Inhibition in a Replication-Dependent Manner.

Simple SummaryThe poor prognosis of patients with TNBC have fostered a major effort to identify more patients who would benefit from targeted therapies. Here we recognize PTEN as a potential CIN-causing gene in TNBC and consider PTEN-deficient TNBC for the treatment with PARP1 inhibitors due to the protective role of PTEN during DNA replication.Chromosomal instability (CIN) is an emerging hallmark of cancer and its role in therapeutic responses has been increasingly attracting the attention of the research community. To target the vulnerability of tumors with high CIN, it is important to identify the genes and mechanisms involved in the maintenance of CIN. In our work, we recognize the tumor suppressor gene Phosphatase and Tensin homolog (PTEN) as a potential gene causing CIN in triple-negative breast cancer (TNBC) and show that TNBC with low expression levels of PTEN can be sensitized for the treatment with poly-(ADP-ribose)-polymerase 1 (PARP1) inhibitors, independent of Breast Cancer (BRCA) mutations or a BRCA-like phenotype. In silico analysis of mRNA expression data from 200 TNBC patients revealed low expression of PTEN in tumors with a high CIN70 score. Western blot analysis of TNBC cell lines confirm lower protein expression of PTEN compared to non TNBC cell lines. Further, PTEN-deficient cell lines showed cellular sensitivity towards PARP1 inhibition treatment. DNA fiber assays and examination of chromatin bound protein fractions indicate a protective role of PTEN at stalled replication forks. In this study, we recognize PTEN as a potential CIN-causing gene in TNBC and identify its important role in the replication processes.

Restoration of tumor suppression in vivo by systemic delivery of chemically-modified PTEN mRNA nanoparticles.

11582 Background: The onset and maintenance of cancer frequently involves gain of oncogenic function along with loss of tumor suppression. PTEN is a well-characterized tumor suppressor gene that is lost or mutated in many human cancers including ~50% of metastatic castration-resistant prostate cancer (mCRPC). Reintroduction of functional PTEN for mCRPC treatment has proven difficult. Methods: PTEN mRNA was synthesized by in vitro transcription method and modified with ARCA capping and enzymatic polyadenylation, and then substituted with Pseudo-UTP, 5’-Methyl-CTP. A robust self-assembly approach was employed to prepare PTEN mRNA nanoparticles (NPs) using cationic lipid-like compound G0-C14 and PLGA polymer coated with lipid-PEG shell. PTEN expression in tumors and PI3K-AKT pathway were confirmed by IHC and western blot, respectively. Apoptosis was checked by flow cytometry and Tunel assays. In vivo toxicity was studied by hematologic and histologic tests, and immune response. Results: We successfully restored PTEN mRNA to PTEN-null prostate cancer (PCa) cells via systemic delivery of mRNA NPs. These mRNA NPs are stable in serum, demonstrate minimal toxicity, and provide highly effective transfection in PCa cells (substantially higher HA-PTEN expression than plasmid PTEN transfection) and PCa xenograft tumors, leading to ~85% inhibition of tumor cell growth in vitro and in vivo. We also confirm mRNA NP-mediated systemic restoration of PTEN function in PTEN-null PCa and delineate its tumor suppression through inhibition of the PI3K-AKT pathway and enhancement of apoptosis. Conclusions: The work provides proof of principle for the systemic reintroduction of mRNA-based tumor suppressor genes to tumors in vivo. Because PTEN loss is frequent in late-stage PCa, this approach may have feasibility in this patient population. Considering the strong potential of mRNA therapy and the lack of systemic studies of in vivo mRNA transfection of tumors, this study sheds light on the useful application of NP-mediated mRNA delivery for validating tumor suppressors (e.g., PTEN) as a therapeutic target in cancer treatment where loss of a tumor suppressor contributes to the underlying genetic mechanism of cancer.