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Haploinsufficient phenotypes promote selection of PTEN and ARID1A deficient clones in human colon

ABSTRACT: Cancer driver mutations are defined by their high prevalence in cancers and presumed rarity in normal tissues. However, recent studies show that positive selection in normal epithelia can increase the prevalence of some cancer drivers. To determine their true cancer-driving potential, it is essential to evaluate how frequent these mutations are in normal tissues and what their phenotypes are. Here, we explore the bioavailability of somatic variants by quantifying age-related mutational burdens in normal human colonic epithelium using immune detection in FFPE samples (N=181 patients). Positive selection of variants of tumour suppressor genes PTEN and ARID1A associates with monoallelic gene loss as confirmed by CRISPR/Cas9 mutagenesis and changes in their downstream effectors. Comparison of the mutational burden in normal tissue and colorectal cancers allows quantification of cancer driver potency based on relative representation. Additionally, immune exclusion, a cancer hallmark feature, is observed within ARID1A-deficient clones in histologically normal tissue. The behaviour resulting from haploinsufficiency of PTEN and ARID1A demonstrates how somatic mosaicism in tumour suppressors arises and can predispose to cancer initiation.

SUBMITTER: Nefeli Skoufou-Papoutsaki

PROVIDER: S-SCDT-10_1038-S44319-025-00373-0 | biostudies-other |

REPOSITORIES: biostudies-other

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Haploinsufficient phenotypes promote selection of PTEN and ARID1A-deficient clones in human colon.

Project description:Cancer driver mutations are defined by their high prevalence in cancers and presumed rarity in normal tissues. However, recent studies show that positive selection in normal epithelia can increase the prevalence of some cancer drivers. To determine their true cancer-driving potential, it is essential to evaluate how frequent these mutations are in normal tissues and what are their phenotypes. Here, we explore the bioavailability of somatic variants by quantifying age-related mutational burdens in normal human colonic epithelium using immunodetection in FFPE samples (N = 181 patients). Positive selection of variants of tumour suppressor genes PTEN and ARID1A associates with monoallelic gene loss as confirmed by CRISPR/Cas9 mutagenesis and changes in their downstream effectors. Comparison of the mutational burden in normal tissue and colorectal cancers allows quantification of cancer driver potency based on relative representation. Additionally, immune exclusion, a cancer hallmark feature, is observed within ARID1A-deficient clones in histologically normal tissue. The behaviour resulting from haploinsufficiency of PTEN and ARID1A demonstrates how somatic mosaicism of tumour suppressors arises and can predispose to cancer initiation.

| S-EPMC11893880 | biostudies-literature

Haploinsufficient phenotypes promote selection of PTEN and ARID1A deficient clones in human colon.

Project description:Normal human tissues are known to be composed of a pactchwork of mutant clones but with limited implications on cancer risk. PTEN and ARID1A deficient clones were detected in the human colon using immunohistrochemistry and were found to be the product of monoallelic loess. They were associated with a bias in clone dynamics which resulted in positive selection in the tissue. Heterozygous mutations were introduced in intestinal organoids which were subjected to bulk RNA-seq to describe the molecular mechanisms behind their positive selection. Although PTEN het organoids were associated with an advantageous phenotype in organoids, which was recapitulated in the transcriptomic analysis with increase proliferation and upregulation of developmental/regenerative processes and metabolic reprogramming, the ARID1A het organoids showed reduced growth which was seen as upregulation of apoptosis and downregulation of DNA replication. The discrepancy between the tissue and organoid phenotype for ARID1A was later explained due to the impact on stromal cells which are found in the tissue and are mediating the selective advantage. Importantly these molecular alterations and behaviours arise due to haploinsufficiency of these tumour suppressors in a pre-neoplastic context.

2024-05-13 | GSE266990 | GEO

Haploinsufficient phenotypes promote selection of PTEN and ARID1A deficient clones in human colon.

Project description:Haploinsufficient phenotypes promote selection of PTEN and ARID1A deficient clones in human colon.

| PRJNA1109299 | ENA

microRNA-143/145 loss induces Ras signaling to promote aggressive Pten-deficient basal-like breast cancer.

Project description:The tumor suppressor PTEN is frequently inactivated in breast and other cancers; yet, germ-line mutations in this gene induce nonmalignant hamartomas, indicating dependency on additional cooperating events. Here we show that most tumors derived from conditional deletion of mouse pten in mammary epithelium are highly differentiated and lack transplantable tumor-initiating cells (TICs) capable of seeding new tumors following orthotopic injection of FACS-sorted or tumorsphere cells. A rare group of poorly differentiated tumors did harbor transplantable TICs. These transplantable tumors exhibited distinct molecular classification, signaling pathways, chromosomal aberrations, and mutational landscape, as well as reduced expression of microRNA-143/145 (miR-143/145). Stable knockdown of miR-143/145 conferred tumorigenic potential upon poorly transplantable pten-deficient tumor cells through a mechanism involving induction of RAS signaling, leading to increased sensitivity to MEK inhibition. In humans, miR-145 deficiency significantly correlated with elevated RAS-pathway activity in basal-like breast cancer, and patients with combined PTEN/miR-145 loss or PTEN-loss/high RAS-pathway activity exhibited poor clinical outcome. These results underscore a selective pressure for combined PTEN loss together with RAS-pathway activation, either through miR-145 loss or other mechanisms, in basal-like breast cancer, and a need to identify and prioritize these tumors for aggressive therapy.

| S-EPMC5543917 | biostudies-literature

PI3K isoform-selective inhibition in neuron-specific PTEN-deficient mice rescues molecular defects and reduces epilepsy-associated phenotypes.

Project description:Epilepsy affects all ages, races, genders, and socioeconomic groups. In about one third of patients, epilepsy is uncontrolled with current medications, leaving a vast need for improved therapies. The causes of epilepsy are diverse and not always known but one gene mutated in a small subpopulation of patients is phosphatase and tensin homolog (PTEN). Moreover, focal cortical dysplasia, which constitutes a large fraction of refractory epilepsies, has been associated with signaling defects downstream of PTEN. So far, most preclinical attempts to reverse PTEN deficiency-associated neurological deficits have focused on mTOR, a signaling hub several steps downstream of PTEN. Phosphoinositide 3-kinases (PI3Ks), by contrast, are the direct enzymatic counteractors of PTEN, and thus may be alternative treatment targets. PI3K activity is mediated by four different PI3K catalytic isoforms. Studies in cancer, where PTEN is commonly mutated, have demonstrated that inhibition of only one isoform, p110β, reduces progression of PTEN-deficient tumors. Importantly, inhibition of a single PI3K isoform leaves critical functions of general PI3K signaling throughout the body intact. Here, we show that this disease mechanism-targeted strategy borrowed from cancer research rescues or ameliorates neuronal phenotypes in male and female mice with neuron-specific PTEN deficiency. These phenotypes include cell signaling defects, protein synthesis aberrations, seizures, and cortical dysplasia. Of note, p110β is also dysregulated and a promising treatment target in the intellectual disability Fragile X syndrome, pointing towards a shared biological mechanism that is therapeutically targetable in neurodevelopmental disorders of different etiologies. Overall, this work advocates for further assessment of p110β inhibition not only in PTEN deficiency-associated neurodevelopmental diseases but also other brain disorders characterized by defects in the PI3K/mTOR pathway.

| S-EPMC7484255 | biostudies-literature

The PTEN Conundrum: How to Target PTEN-Deficient Prostate Cancer.

Project description:Loss of the tumor suppressor phosphatase and tensin homologue deleted on chromosome 10 (PTEN), which negatively regulates the PI3K-AKT-mTOR pathway, is strongly linked to advanced prostate cancer progression and poor clinical outcome. Accordingly, several therapeutic approaches are currently being explored to combat PTEN-deficient tumors. These include classical inhibition of the PI3K-AKT-mTOR signaling network, as well as new approaches that restore PTEN function, or target PTEN regulation of chromosome stability, DNA damage repair and the tumor microenvironment. While targeting PTEN-deficient prostate cancer remains a clinical challenge, new advances in the field of precision medicine indicate that PTEN loss provides a valuable biomarker to stratify prostate cancer patients for treatments, which may improve overall outcome. Here, we discuss the clinical implications of PTEN loss in the management of prostate cancer and review recent therapeutic advances in targeting PTEN-deficient prostate cancer. Deepening our understanding of how PTEN loss contributes to prostate cancer growth and therapeutic resistance will inform the design of future clinical studies and precision-medicine strategies that will ultimately improve patient care.

| S-EPMC7690430 | biostudies-literature

PTEN-deficient cancers depend on PIK3CB.

Project description:Deregulation of the PI3K signaling pathway is observed in many human cancers and occurs most frequently through loss of PTEN phosphatase tumor suppressor function or through somatic activating mutations in the Class IA PI3K, PIK3CA. Tumors harboring activated p110alpha, the protein product of PIK3CA, require p110alpha activity for growth and survival and hence are expected to be responsive to inhibitors of its lipid kinase activity. Whether PTEN-deficient cancers similarly depend on p110alpha activity to sustain activation of the PI3K pathway has been unclear. In this study, we used a single-vector lentiviral inducible shRNA system to selectively inactivate the three Class IA PI3Ks, PIK3CA, PIK3CB, and PIK3CD, to determine which PI3K isoforms are responsible for driving the abnormal proliferation of PTEN-deficient cancers. Down-regulation of PIK3CA in colorectal cancer cells harboring mutations in PIK3CA inhibited downstream PI3K signaling and cell growth. Surprisingly, PIK3CA depletion affected neither PI3K signaling nor cell growth in 3 PTEN-deficient cancer cell lines. In contrast, down-regulation of the PIK3CB isoform, which encodes p110beta, resulted in pathway inactivation and subsequent inhibition of growth in both cell-based and in vivo settings. This essential function of PIK3CB in PTEN-deficient cancer cells required its lipid kinase activity. Our findings demonstrate that although p110alpha activation is required to sustain the proliferation of established PIK3CA-mutant tumors, PTEN-deficient tumors are dependent instead on p110beta signaling. This unexpected finding demonstrates the need to tailor therapeutic approaches to the genetic basis of PI3K pathway activation to achieve optimal treatment response.

| S-EPMC2529105 | biostudies-literature

Selection of Oncogenic Mutant Clones in Normal Human Skin Varies with Body Site.

Project description:Skin cancer risk varies substantially across the body, yet how this relates to the mutations found in normal skin is unknown. Here we mapped mutant clones in skin from high- and low-risk sites. The density of mutations varied by location. The prevalence of NOTCH1 and FAT1 mutations in forearm, trunk, and leg skin was similar to that in keratinocyte cancers. Most mutations were caused by ultraviolet light, but mutational signature analysis suggested differences in DNA-repair processes between sites. Eleven mutant genes were under positive selection, with TP53 preferentially selected in the head and FAT1 in the leg. Fine-scale mapping revealed 10% of clones had copy-number alterations. Analysis of hair follicles showed mutations in the upper follicle resembled adjacent skin, but the lower follicle was sparsely mutated. Normal skin is a dense patchwork of mutant clones arising from competitive selection that varies by location. SIGNIFICANCE: Mapping mutant clones across the body reveals normal skin is a dense patchwork of mutant cells. The variation in cancer risk between sites substantially exceeds that in mutant clone density. More generally, mutant genes cannot be assigned as cancer drivers until their prevalence in normal tissue is known.See related commentary by De Dominici and DeGregori, p. 227.This article is highlighted in the In This Issue feature, p. 211.

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The kinase PLK1 promote melanoma progression in the BRAFV600E/PTEN-deficient mouse

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RAD-Deficient Human Cardiomyocytes Develop Hypertrophic Cardiomyopathy Phenotypes Due to Calcium Dysregulation.

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