Loss Of PTEN Expression Research Articles

TERT mutations and aggressive histopathologic characteristics of radioiodine-refractory papillary thyroid cancer.

Radioiodine (RI) ablation following thyroid-stimulating hormone suppression is an effective treatment for papillary thyroid cancer (PTC), typically leading to favorable outcomes. However, RI-refractory tumors exhibit aggressive behavior and poor prognoses. Recent studies highlight the role of genetic abnormalities in PTC signaling pathways, including the activation of telomerase reverse transcriptase (TERT), and the correlation of mutations with adverse outcomes. This study analyzed mutations in BRAF V600E and the TERT-promoter genes, comparing clinicopathological features between RI-refractory and RI-responsive PTCs. Among 82 RI-refractory patients, formalin-fixed, paraffin-embedded tissues from initial surgeries were available for 26. Another 89 without distant metastasis over 5 years formed a matched RI-responsive control group. Histopathologically, RI-refractory PTCs showed increased frequencies of small tumor clusters without fibrovascular cores, hobnail features, and a high height-to-width ratio of tumor cells. These tumors were more likely to exhibit necrosis, mitosis, lymph node metastasis, extrathyroidal extension, and involvement of resection margins. TERT-promoter mutations were statistically significantly associated with these aggressive clinicopathologic features. Immunohistochemically, decreased expression of sodium iodide symporter and thyroglobulin stimulating hormone receptor proteins was common in RI-refractory PTCs, along with lower levels of oncogenic proteins such as vascular endothelial cell growth factor, vascular endothelial cell growth factor receptor 2, and nuclear factor kappa-light-chain-enhancer of activated B cells. Total loss of PTEN expression was occasionally observed. In contrast, all cases tested positive for cytoplasmic β-catenin. RI-refractory PTCs are linked to TERT mutations and exhibit specific aggressive histopathologic features, particularly in tumor centers.

Endometrioid ovarian carcinoma landscape: pathological and molecular characterization.

Endometrioid ovarian cancers (EOvC) are usually managed as serous tumors. In this study, we conducted a comprehensive molecular investigation to uncover the distinct biological characteristics of EOvC. This retrospective multicenter study involved patients from three European centers. We collected clinical data and formalin-fixed paraffin-embedded (FFPE) samples for analysis at the DNA level using panel-based next-generation sequencing and array-comparative genomic hybridization. Additionally, we examined mRNA expression using NanoString nCounter® and protein expression through tissue microarray. We compared EOvC with other ovarian subtypes and uterine endometrioid tumors. Furthermore, we assessed the impact of molecular alterations on patient outcomes, including progression-free survival (PFS) and overall survival (OS). Preliminary analysis of clinical data from 668 patients, including 86 (12.9%) EOvC, revealed more favorable prognosis for EOvC compared with serous ovarian carcinoma (5-year OS of 60% versus 45%; P = 0.001) driven by diagnosis at an earlier stage. Immunohistochemistry and copy number alteration (CNA) profiles of 43 cases with clinical data and FFPE samples available indicated that EOvC protein expression and CNA profiles were more similar to endometrioid endometrial tumors than to serous ovarian carcinomas. EOvC exhibited specific alterations, such as lower rates of PTEN loss, mutations in DNA repair genes, and P53 abnormalities. Survival analysis showed that patients with tumors harboring loss of PTEN expression had worse outcomes (median PFS 19.6 months vs. not reached; P = 0.034). Gene expression profile analysis confirmed that EOvC differed from serous tumors. However, comparison to other rare subtypes of ovarian cancer suggested that the EOvC transcriptomic profile was close to that of ovarian clear cell carcinoma. Downregulation of genes involved in the PI3K pathway and DNA methylation was observed in EOvC. In conclusion, EOvC represents a distinct biological entity and should be regarded as such in the development of specific clinical approaches.

The Clinicopathological Correlation of KRAS Mutation and PTEN Expression Status in Primary and Metastatic Colorectal Carcinoma.

Colorectal cancer (CRC) researchhas identified a consistent loss of PTEN expression in both primary tumors and metastasis, highlighting its potential role in this disease. However, the impact of PTEN on downstream proteins of KRAS mutation, namely p-AKT, p-ERK, and p65 (NFkB), remains unknown. This study aims to explore the inhibitory effect of PTEN on KRAS downstream proteins and its correlation with pathological features in CRC patients. From January 1, 2015, to December 31, 2021, 86 CRC cases were collected from governmental and private laboratories in the Duhok province. Formalin-fixed, paraffin-embedded tissue blocks were obtained, and the study involved histopathological analysis, immunohistochemistry of PTEN, AKT, ERK, and P65 markers, and molecular analysis of the KRAS gene. Among the 86 cases, there were 46 males (53.5%) and 40 females (46.5%), with an equal distribution between right colon and left colon/rectum. Tumors larger than 5cm were observed in 47 cases, predominantly displaying a polypoid or ulcerated growth pattern. Most cases were moderately differentiated adenocarcinomas, with stages II and III being the most prevalent 31 cases (36%) and 34 cases (39.5%) respectively. Significant associations were found between PTEN, ERK expressions, and tumor location in the right colon (P=0.031 and P=0.009 respectively). Tumor size correlated with P65 expression (P=0.042). KRAS mutation showed a positive relationship with the type of tumor growth (P=0.035). Tumor grade increased with KRAS mutations (P=0.043). PTEN expression correlated significantly with ERK and AKT markers (P=0.018 and 0.035 respectively). P65 exhibited an association with KRAS mutation (P=0.034). The study revealed PTEN expression in association with the inhibition of AKT and ERK, and the absence of KRAS gene mutation. Conversely, PTEN is not expressed with the positively reactive P65 and the presence of KRAS mutation. This study contributes valuable insights into the complex interplay between PTEN expression, KRAS mutation, and downstream signaling pathways in CRC. It suggests potential avenues for further research and therapeutic strategies in the context of CRC treatment.

PTEN, ERG, SPINK1, and TFF3 Status and Relationship in a Prostate Cancer Cohort from Jordanian Arab Population.

Background and Objectives: Prognostic biomarkers in prostate cancer (PCa) include PTEN, ERG, SPINK1, and TFF3. Their relationships and patterns of expression in PCa in developing countries, including Jordan, have not yet been investigated. Materials and Methods: A tissue microarray (TMA) of PCa patients was taken from paraffin-embedded tissue blocks for 130 patients. PTEN, ERG, SPINK1, and TFF3 expression profiles were examined using immunohistochemistry (IHC) and correlated with each other and other clinicopathological factors. Results: PTEN loss of any degree was observed in 42.9% of PCa cases. ERG and TFF3 were expressed in 59.3% and 46.5% of PCa cases, respectively. SPINK1 expression was observed in 6 out of 104 PCa cases (5.4%). Among all PCa cases (n = 104), 3.8% (n = 4) showed SPINK1+/ERG+ phenotype, 1.9% (n = 2) showed SPINK1+/ERG- phenotype, 56.7% (n = 59) showed SPINK1-/ERG+ phenotype, and 37.5% showed SPINK1-/ERG- phenotype (n = 39). Among ERG positive cases (n = 63), 6.3% were SPINK1 positive. Among SPINK1 positive cases (n = 6), 66.7% were ERG positive. SPINK1 expression was predominantly observed in a subgroup of cancers that expressed TFF3 (6/6). Additionally, a statistically significant loss of PTEN expression was observed from Gleason Score 6 (GS6) (Grade Group 1 (GG1)) to GS9-10 (GG5); (p-value 0.019). Conclusions: This is the first study to look at the status of the PTEN, ERG, SPINK1, and TFF3 genes in a Jordanian Arab population. Loss of PTEN has been linked to more aggressive prostate cancer with high GSs/GGs. SPINK1 expression was predominantly observed in a subgroup of cancers that expressed TFF3. Our results call for screening these biomarkers for grading and molecular subtyping of the disease.

Interactions of EGFR/PTEN/mTOR-Pathway Activation and Estrogen Receptor Expression in Cervical Cancer.

(1) Objective: Late-line chemotherapy rechallenge in recurrent cervical cancer is associated with modest therapy response but significant side effects. As mTOR pathways modulate cellular growth via estrogen receptor (ER) signaling and combined mTOR and ER inhibition previously demonstrated survival benefits in breast cancer, this exploratory study evaluates mTOR pathway and ER expression interactions in a preclinical cervical cancer model. (2) Methods: Immunostaining of a 126-tumor core tissue microarray was performed to assess phosphorylated-mTOR and ER expression. To identify tumor subsets with different clinical behavior, expression results were matched with clinicopathologic patient characteristics, and both univariate and multivariable survival statistics were performed. (3) Results: phosphorylated-mTOR correlates with ER (r = 0.309, p < 0.001) and loss of PTEN expression (r = -2.09, p = 0.022) in tumor samples across stages but not in matched negative controls. Positive ER expression is observed significantly more often in phosphorylated-mTOR positive samples (30.0% vs. 6.3%, p = 0.001). In the subgroup of phosphorylated-mTOR positive tumors (n = 60), ER expression is associated with improved survival (p = 0.040). (4) Conclusion: ER expression appears closely intertwined with EGFR/PTEN/mTOR-pathway activation and seems to define a subgroup with clinically distinct behavior. Considering limited therapeutic options in recurrent cervical cancer, further validation of combined mTOR and ER inhibition in selected patients could appear promising.

PTEN Expression and Specific Clinicopathological Associations in Colorectal Carcinomas

Introduction: Colorectal carcinoma (CRC) refers to any cancerthat affects the colon and the rectum and it is a significantpublic health issue.1 It is the third most common cancer to bediagnosed globally and the fourth most frequent reason forcancer-related mortality. The diagnosis of CRCs occurs inplaces with affluent economies about 60% of the time. Thepresent study assessed phosphatase and tensin homolog(PTEN) expression in colorectal cancer and its associationwith tumor characteristics.Materials and Methods: The study was carried out over thecourse of 18 months, from 1 February 2021 to 31 July 2022, atthe SRMS IMS Bareilly Department of Pathology. The analysisincluded surgically removed specimens of colorectal cancerthat had been obtained at the SRMS, IMS Department ofPathology. The patient’s medical records provided the clinicalinformation.Results: Loss of PTEN expression was seen in 76.9% of CRCcases, while 23.1% of cases revealed positive expression.Maximum cases were of age&gt;60 years and male predominancewas noted. In 62.5% of cases with tumor size ≥5 cm displayedloss of PTEN expression. In 52.5% loss of PTEN tumor caseswere histologically moderately differentiated, 37.5% were welldifferentiated, and 10% were poorly differentiated. 50% of caseswith pathologic tumor stage (pT3) and 65% left-sided tumorsshowed loss of PTEN expression.Conclusion: Loss of PTEN expression was observed in themajority of colorectal tumors along with its negative associationwith tumor size and pathologic tumor staging.

Association Between ERG/PTEN Genes and Pathologic Parameters of Prostate Cancer With an Emphasis on Gleason Score: A Literature Review.

The purpose of this article was to review the association between the ETS-related gene (ERG) and the phosphatase and tensin homolog (PTEN) genes with pathologic parameters of prostate cancer, emphasizing on Gleason score. We performed a PubMed-based search of the literature emphasizing on articles that use pathological techniques, and especially on those that report the use immunohistochemical staining and FISH to investigate the association between ERG and PTEN mutations with the histopathologic parameters of prostate cancer. ERG expression is frequently marked in patients with prostate cancer, usually due to the occurrence of the TMPRSS2:ERG gene fusion. Although some studies reported a potential link between the expression of ERG and Gleason score, there is no strong evidence supporting this finding. On the contrary, there is more solid evidence correlating loss of PTEN expression with worse prognosis and higher Gleason scores. Few studies correlate the over-expression of ERG gene with the loss of PTEN expression. Finally, PTEN and ERG have been studied as potential therapeutic targets, and several promising results have been reported. Although, at some degree, ERG expression seems to be associated with the morphological features of prostate cancer, different studies reported controversial results. However, expression of PTEN is more clearly associated with the pathology and clinical course of the disease. More research is required to elucidate the role of these molecules in the molecular pathology of prostate cancer, as well as their potential use as therapeutic targets.

Malignant transformation of endometrial hyperplastic processes: immunohistochemical features

Background. Endometrial hyperplasia is one of the most common pathologies of the female reproductive system. There is a high risk of transformation of an atypical form of endometrial hyperplasia into endometrial cancer, which takes a leading position in oncogynecological morbidity. Immunohistochemical markers can become predictors of endometrial malignancy, their role is currently being actively studied.Aim. Search for molecular predictors of malignant transformation of endometrial hyperplasia.Materials and methods. Histological and immunohistochemical studies were performed in 107 patients with diagnoses of endometrial hyperplasia without atypia (EH), endometrial atypical hyperplasia (EIN), endometrioid adenocarcinoma (EC). The tumor receptor status, MSI, expression of ARID1A, PTEN, β-catenin, PAX2, proliferation index (Ki-67) were determined by the immunohistochemical method according to the standard protocol.Results. Loss of PAX2 expression was most common in precancerous and malignant endometrial cells. Loss of PAX2 expression was found in 89 % of cases in the EIN samples, in 86 % of cases in the EC samples and only in 2 cases of EH. Loss of PTEN expression was less common: with an equal proportion in 67 % of the samples of EIN and EC, while practically not occurring in women with benign GE. MSI was detected in 36 % of endometrial cancer samples. There was a deficiency in the DNA repair system in 1 case of EIN. Loss of ARID1A expression was detected in endometrial cancer with a frequency of 33 %. This gene functioned normally in all cases of EIN and EH. The expression of β-catenin was more pronounced in EC than in cases of EH. The Ki-67 proliferation index was statistically higher in the EC group than in EH and EIN.Conclusion. Evaluation of morphological data and expression of the panel of markers PAX2, PTEN, ARID1A, β-catenin, Ki-67 index, PMS2 and MLH1 will improve diagnostic search in case of suspected malignancy of endometrial hyperplasia.

An Immunohistochemical Study for Mammalian Target of Rapamycin Signaling Pathway Including Interacting PTEN in Prostatic Acinar Adenocarcinoma and Correlation with the Patient Clinicopathological Parameters

Background: The activation of AKT-mTOR-PTEN pathway may promote prostate cancer progression and affects response to targeted therapies. The full extent of this activation remains to be determined. Our aim: was to assess the expression of inactive mTOR, phosphor-mTOR, phosphor-AKT and loss of PTEN in prostatic adenocarcinomas then correlate their expression with the clinicopathological parameters.&#x0D; Methods: The study included 166 prostatic adenocarcinoma tissues using immunohistochemistry on tissue microarrays. Statistical analysis considering markers expression and correlation with the clinicopathologic parameters was done using appropriate tests.&#x0D; Result: The mean age was 72.63 and 75.9% were clinically high risk. Gleason score 7 and WHO grade group 5 were the commonest (31.3% and 31.9% respectively). Most patient (73.1%) were stage T2 or higher. Expression of inactive mTOR, phospho-mTOR and phosphor-AKT was seen in 96.1%, 93.5% and 95.9% respectively. The loss of PTEN expression was noted in 55.3%. There were significant correlations between Gleason pattern 4 and the expression of inactive mTOR (p value &lt;0.001 and 0.004 respectively) and phospho-mTOR (p value 0.003 and 0.001 respectively). Gleason score 7 was significantly correlated to inactive mTOR expression (p value &lt;0.001). There was also significant correlation between phosphor-AKT and phospho- mTOR expression with p value 0.004.&#x0D; Conclusion: The immunohistochemical expression of inactive mTOR, phosphor-mTOR and phosphor-AKT and loss of PTEN was appreciated in most prostate cancer cases, suggesting that activation of this pathway occur early during prostate tumorigenesis. This may indicate that targeting mTOR pathway may have a promising therapeutic role in the management of prostatic adenocarcinoma.

Phosphatase and Tensin Homolog Immunohistochemical Expression and Promoter Methylation Status in Endometrioid Endometrial Carcinoma and Its Precursor Lesions.

Endometrioid endometrial carcinoma (EEC) is the most common invasive malignancy of the female genital tract. Despite advances in diagnosis and treatment, the incidence of EEC and mortality related to it have not decreased. Therefore, research is needed to explore the underlying molecular mechanisms of EEC and its precursors to reduce the mortality and societal burden associated with them. Phosphatase and tensin homolog (PTEN) is a tumor suppressor gene most commonly altered in endometrial carcinoma and its precursor lesions. Promoter methylation is a common mechanism for the inactivation of the PTEN tumor suppressor gene. This was a prospective nested case-control study involving women aged 35 to 70 years old whose endometrial biopsy and resected samples were obtained for histological diagnosis. Before enrolling a person in the study, signed informed consent was obtained from each individual. The ethics committee for the institute gave its approval to the study protocol. Immunohistochemistry (IHC) was used to measure PTEN expression was measured, and methylation-specific PCR (MSP) was used to determine PTEN promoter methylation status (Bisulfite conversion). A total of 95 samples were assessed histopathologically, along withPTEN expression and PTEN promoter methylation status. PTEN immunoreactivity was observed in 79% (15/19) of normal proliferative endometrium, and loss of PTEN expression was observed in 73% (27/37) of endometrial hyperplasia with or without atypia and 90% (35/39) of EEC. Methylation analysis showed that the PTEN promoter was completely unmethylated in all normal proliferative endometria and endometrial hyperplasia without atypia. In contrast, the promoter region was methylated in 50% of endometrial hyperplasia with atypia cases and 38.5% of EEC cases. The loss ofPTEN expression was significantly associated with EEC and precancerous lesions of the endometrium compared to normal proliferative endometria. Methylation analysis also revealed that the frequency of methylation is significant in EEC and endometrial hyperplasia with atypia. Integration of PTEN protein expression along with promoter methylation status elucidates the underlying carcinogenic mechanism. This may help with personalized therapy for EECs and triaging cases of potential precancerous lesions.

PTEN loss promotes Warburg effect and prostate cancer cell growth by inducing FBP1 degradation.

RationaleFructose-1,6-bisphosphatase (FBP1) is a tumor suppressor and a key enzyme negatively regulating Warburg effect in cancer. However, regulation of FBP1 protein expression and its exact role in prostate cancer (PCa) is largely unclear. Phosphatase and tensin homolog (PTEN) is one of the most frequently deleted tumor suppressor genes in human PCa. However, the role of PTEN loss in aberrant Warburg effect in cancer remains poorly understood.MethodsExpression of PTEN and FBP1 was analyzed in several PCa cell lines and prostate tumor tissues in mice. Western blot (WB) and RT-PCR approaches were used to examine how PTEN regulates FBP1 expression. Co-immunoprecipitation (co-IP) and in vivo ubiquitination assays were used to define the regulatory mechanisms. A PCa xenograft model was employed to determine the impact of PTEN regulation of FBP1 on PCa growth in vivo.ResultWe demonstrated that in a manner dependent of PI3K/AKT signal pathway PTEN regulated FBP1 expression in various PCa cell lines and tumors in mice. We confirmed that this regulation took place at the protein level and was mediated by SKP2 E3 ubiquitin ligase. Mechanistically, we showed that serine 271 phosphorylation of FBP1 by cyclin-dependent kinases (CDKs) was essential for SKP2-mediated degradation of FBP1 protein induced by PTEN loss. Most importantly, we further showed that loss of PTEN expression enhanced Warburg effect and PCa growth in mice in a manner dependent, at least partially on FBP1 protein degradation.ConclusionsOur results reveal a novel tumor-suppressive feature of PTEN in restraining FBP1 degradation and the Warburg effect. These results also suggest that prohibiting FBP1 protein degradation could be a viable therapeutic strategy for PTEN-deficient PCa.

Loss of PTEN Expression, PIK3CA Mutations, and Breast Cancer Survival in the Nurses' Health Studies.

The relationships between PTEN loss and/or PIK3CA mutation and breast cancer prognosis remain controversial. We aim to examine the associations in large epidemiologic cohorts. We followed women with invasive breast cancer from the Nurses' Health Studies with available data on tumor PTEN expression (n = 4,111) and PIK3CA mutation (n = 2,930). PTEN expression was evaluated by IHC and digitally scored (0%-100%). Pyrosequencing of six hotspot mutations of PIK3CA was performed. We found loss of PTEN expression (≤10%) occurred in 17% of cases, and PIK3CA mutations were detected in 11% of cases. After adjusting for clinical and lifestyle factors, PTEN loss was not associated with worse breast cancer-specific mortality among all samples [HR, 0.85; 95% confidence intervals (CI), 0.71-1.03] or among estrogen receptor (ER)-positive tumors (HR, 0.99; 95% CI, 0.79-1.24). However, among ER-negative tumors, PTEN loss was associated with lower breast cancer-specific mortality (HR, 0.68; 95% CI, 0.48-0.95). PIK3CA mutation was not strongly associated with breast cancer-specific mortality (HR, 0.89; 95% CI, 0.67-1.17). Compared with tumors without PTEN loss and without PIK3CA mutation, those with alterations (n = 540) were not at higher risk (HR, 1.07; 95% CI, 0.86-1.34). However, women with both PTEN loss and PIK3CA mutation (n = 38) were at an increased risk of breast cancer-specific mortality (HR, 1.65; 95% CI, 0.83-3.26). In this large epidemiologic study, the PTEN-mortality association was more pronounced for ER-negative tumors, and the joint PTEN loss and PIK3CA mutation may be associated with worse prognosis. Further studies with a larger sample of ER-negative tumors are needed to replicate our findings and elucidate underlying mechanisms.

Abstract 2220: Immunohistochemical detection of prostate cancer heterogeneity by using ETS and PTEN monoclonal antibodies

Abstract The multifocality and highly variable molecular pathology of prostate cancer are underlying features of this clinically heterogeneous disease. Most patients harbor multiple molecularly distinct cancer foci at diagnosis that likely arose as independent clones. There is a critical need for molecular biomarkers that can distinguish the multifocality and inter-focal heterogeneity of tumors and help stratify patients for treatment. PTEN loss and ETS gene rearrangements are among the most prevalent genomic alterations in prostate carcinogenesis. The detection of both ERG overexpression and PTEN protein loss by immunohistochemistry (IHC) have proven to be reliable substitutes for detecting genomic alterations by fluorescence in situ hybridization (FISH) assay. We developed monoclonal antibodies against ETV1 and ETV4 and evaluated their performance in prostate cancer specimens. The expression of ETV1, ETV4, were examined in relation to ERG and loss of PTEN expression in TMAs constructed from primary prostate cancer specimens of two independent patient cohorts. The first TMA was constructed from multiple 1 mm cores representing distinct tumor focus from multifocal tumors from 50 African American (AA) and 50 Caucasian American (CA) men. The second was constructed from a single 2 mm core of individual tumors from an independent cohort of 152 AA and 304 CA men. We present results on the expression of each protein biomarker in the context of patient race and their association with clinico-pathologic features, together with concurrence or mutual exclusiveness for each event. These results support the application of ETS monoclonal antibodies in IHC assays to detect prostate cancer tumor heterogeneity and to identify subsets of prostate cancer. Citation Format: Cara Schafer, Denise Young, Yingjie Song, Jiji Jiang, Albert Dobi, Gyorgy Petrovics, Bettina F. Drake, Gregory T. Chesnut, Isabell A. Sesterhenn, Shyh-Han Tan. Immunohistochemical detection of prostate cancer heterogeneity by using ETS and PTEN monoclonal antibodies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2220.

Abstract 3085: Establishment and characterization of two novel patient-derived organoid xenograft models of advanced prostate cancer

Abstract Introduction: An important clinical need remains to improve survival of men with advanced metastatic prostate cancer (PCa). A better understanding of the mechanisms underlying PCa progression and treatment resistance is a prerequisite to address this challenge, which is currently limited by the scarcity of experimental models. Here, we aimed at establishing and characterizing new patient-derived organoids xenograft (PDOX) models of advanced PCa. Materials &amp; methods: We used two patient-derived organoid lines (PDOs), previously generated in our laboratory. P20-11 PDOs were derived from a lung metastasis obtained from a patient with hormone-naïve PCa. P20-23 PDOs were derived from a transurethral prostate resection obtained from a patient with metastatic castration-resistant PCa, previously treated with goserelin, docetaxel, and enzalutamide. PDOX were generated by subcutaneous injection of PDOs in NOD scid gamma (NSG) male mice. Organoids were derived from the PDOX tumors (PDOX-O). Matched patients’ tumor, PDOs, PDOX and PDOX-O samples were characterized using immunohistochemistry (IHC), immunofluorescence (IF), and whole exome sequencing (WES). Organoids were treated with different concentrations of drugs and cell viability was measured using CellTiter-Glo 3D, after a 5-day long treatment. Results: P20-11 PDOs developed tumors in 2 out of 6 mice, 10 months after injection. IHC analysis highlighted a loss of PTEN expression, overexpression of ERG and P53, as well as strong AR and NKX3.1 expression in the tumor, PDOs, PDOX and PDOX-O samples. WES analysis uncovered mutations in CTNNB1, PTEN and TP53 in all samples, and approximately 87% of shared non-synonymous mutations between the PDOX and the original patients’ tumor. Similar to the original PDOs, P20-11 PDOX-O displayed androgen sensitivity in vitro. P20-23 PDOs formed tumors in 3 out of 3 mice 8 months following injection. IHC and IF analyses highlighted a strong expression of CK8, PSMA, AR and NKX3.1, as well as a loss of PTEN expression in the tumor, PDOs, PDOX and PDOX-O samples. WES identified a pathogenic mutation in the PCa-associated gene ZMYM3 in all samples, associated with loss of protein expression. The activating AR point mutation L702H, previously linked to AR signaling inhibitors resistance, was detected in the tumor and in 2 out of 3 PDOX and their derived organoids. Overall, an average of 80% of non-synonymous mutations were shared between the patients’ tumor and PDOX. Finally, P20-23 PDOX-O did not respond to docetaxel or enzalutamide but exhibited sensitivity to the PI3K/AKT inhibitor ipatasertib. Conclusion: We have successfully generated two novel PDOX models, which highly resemble the original patients’ tumor and can be further cultured as organoids. These models are representative of relevant clinical and molecular subtypes of advanced PCa, providing further opportunities for translational studies. Citation Format: Raphaëlle Servant, Zoi Diamantopoulou, Michele Garioni, Luca Roma, Tatjana Vlajnic, Arnoud J. Templeton, Heike Pueschel, Salvatore Piscuoglio, Nicola Aceto, Helge Seifert, Cyrill A. Rentsch, Bubendorf Lukas, Clémentine Le Magnen. Establishment and characterization of two novel patient-derived organoid xenograft models of advanced prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3085.

Abstract 2422: Migration of V600E-expressing cells is suppressed by ERK-dependent feedback inhibition of RAC1 and rescued in melanoma by secondary mutations

Abstract Oncogenic activation of ERK occurs in as many as 50% of human tumors and in the majority of melanomas. Activated BRAF V600E hyperactivates ERK signaling and causes ERK dependent dysregulation of proliferation. However, BRAF V600E alone is insufficient to drive melanoma formation in genetically engineered mice models. Moreover, 82% of benign nevi harbor BRAF V600E mutations. In contrast, in BRAF V600E/PTEN-/- GEMM models, rapid onset of aggressive and disseminated melanomas occurs. We show here that cell migration and invasion of melanocytes expressing BRAFV600E is depressed in vitro and in vivo and significantly accelerated by pharmacologic inhibition of ERK signaling or by deletion of PTEN. Upon ERK inhibition, cells lose their cell-cell junctions and become single cells with actin rich protrusions and a mesenchymal morphology. ERK pathway activation affects each step of the migration cycle, impeding cell spreading, assembly of stress fibers, and focal contact formation, all of which are associated with decreased mobility and invasion. Hyperactivation of ERK signaling by BRAF V600E has been shown to cause potent feedback inhibition of RTK signaling and wild type RAS. We now show that this is associated with feedback inhibition of RAC1, a RAS-like small GTPase required for cell migration. Moreover, ERK pathway inhibition reactivates RAC in an RTK-dependent manner. Consistent with these findings, expression of RAC1 P29S, an activating mutant, and overexpression of PREX2, an activator of RAC1, both rescue migration in BRAF V600E cells, as does loss of PTEN expression, which converges with RAC1 activation downstream. Taken together, these data suggest that whereas hyperactivation of ERK signaling by BRAFV600E dysregulates proliferation, ERK dependent feedback inhibition of RAC1 inhibits cell mobility and invasiveness and prevents full transformation. Selection of secondary genetic events that overcome or bypass RAC1 feedback is thus required for full transformation. In support of this view, RAC1 mutation, PTEN loss, or PREX2 amplification occurs in 38% of human melanomas. Thus, oncogene induced feedback may be deleterious and directs tumor evolution by causing selection of mutations that restore functions necessary for transformation Citation Format: Sunyana Gadal, Jacob A. Boyer, Hongyan Li, Ning Fan, Eric Chan, Yevgeniy Romin, Elisa De Stanchina, Rona Yeager, Marcus Bosenberg, Katia M. Todorova, Neal Rosen. Migration of V600E-expressing cells is suppressed by ERK-dependent feedback inhibition of RAC1 and rescued in melanoma by secondary mutations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2422.

Cancer-Associated Fibroblasts Confer Gemcitabine Resistance to Pancreatic Cancer Cells through PTEN-Targeting miRNAs in Exosomes.

Simple SummaryPrevious studies have shown that cancer associated fibroblasts exposed to chemotherapy release exosomes which promote chemoresistance in recipient cells. However, the molecular mechanism responsible for this has not been fully elucidated. In this study, we found that gemcitabine treatment caused fibroblasts to release exosome which contain PTEN-targeting miRNAs. These findings shed light on how fibroblasts exposed to chemotherapy promote tumor growth and drug resistance.Pancreatic ductal adenocarcinoma (PDAC) is currently the third leading cause of cancer-related death in the United States. Even though the poor prognosis of PDAC is often attributed to late diagnosis, patients with an early diagnosis who undergo tumor resection and adjuvant chemotherapy still show tumor recurrence, highlighting a need to develop therapies which can overcome chemoresistance. Chemoresistance has been linked to the high expression of microRNAs (miRs), such as miR-21, within tumor cells. Tumor cells can collect miRs through the uptake of miR-containing lipid extracellular vesicles called exosomes. These exosomes are secreted in high numbers from cancer-associated fibroblasts (CAFs) within the tumor microenvironment during gemcitabine treatment and can contribute to cell proliferation and chemoresistance. Here, we show a novel mechanism in which CAF-derived exosomes may promote proliferation and chemoresistance, in part, through suppression of the tumor suppressor PTEN. We identified five microRNAs: miR-21, miR-181a, miR-221, miR-222, and miR-92a, that significantly increased in number within the CAF exosomes secreted during gemcitabine treatment which target PTEN. Furthermore, we found that CAF exosomes suppressed PTEN expression in vitro and that treatment with the exosome inhibitor GW4869 blocked PTEN suppression in vivo. Collectively, these findings highlight a mechanism through which the PTEN expression loss, often seen in PDAC, may be attained and lend support to investigations into the use of exosome inhibitors as potential therapeutics to improve the effectiveness of chemotherapy.

Clinicopathological Significance of PTEN Expression and Its Prognostic Effect in Colorectal Adenocarcinoma Patients.

Background & Objective:Phosphatase and tensin homolog (PTEN) is a tumor suppressor gene located at chromosome 10. PTEN is a regulator of the PI3K/AKT signaling pathway that inhibits cell proliferation and promotes apoptosis. PTEN loss of function occurs in a spectrum of cancers, including colorectal adenocarcinoma. This study aimed to investigate the probable correlation of negative PTEN expression with clinicopathological features and colorectal adenocarcinoma (CRC) patients' survival. Methods:In this cross-sectional study using Immunohistochemistry stainingPTEN expression status on 151 CRC tissues was evaluated. Then the results of IHC staining was compared to those of clinicopathological features. The relationship between PTEN and KRAS mutation status was also investigated.Results:Of 151 CRC samples, 89 (58.9%) were negative for PTEN expression. Loss of PTEN expression was associated with KRAS mutation (P<0.0001), lymph node metastasis (P=0.002), and advanced tumor stage (P=0.016), whereas no significant association was found with other clinicopathological features. Multivariate analysis indicated that tumor site and KRAS mutation were independent prognostic CRC patients (P<0.05). The Kaplan-Meier analysis indicated a correlation between loss of PTEN expression and overall survival of patients with colorectal adenocarcinoma (P= 0.01). Conclusion:The current study suggests that decreasing PTEN expression or its negative expression may be associated with a higher stage and poor prognosis. Combined analysis of mutated KRAS and PTEN expression could be a good predictor of disease prognosis as well as its clinical outcomes.

PTEN alterations in sporadic and BRCA1-associated triple negative breast carcinomas

The similarities between sporadic basal-like breast cancer (BLBC) and BRCA1-mutated breast tumours raise the possibility that deregulation of the same pathway may underlie these tumour types. The aim of this study was to determine if PTEN aberrations are characteristic of both BRCA1 tumours and sporadic TN breast carcinomas with low BRCA1 expression, and can thus be used to identify sporadic tumours potentially sensitive to PARP inhibitors. Twelve BRCA1 tumours, 19 non-BRCA familial breast tumours and 71 unselected TN breast carcinomas were screened for PTEN mutations and assessed for PTEN expression and BRCA1 mRNA expression. Loss of PTEN expression was observed in 67% of BRCA1 tumours and more specifically in 89% of TN BRCA1 tumours highlighting the link between PTEN loss and BLBC in the context of germline BRCA1 mutations. Regarding unselected TN tumours, 56% showed PTEN expression loss and 35% displayed low BRCA1 mRNA expression. Unlike familial breast cancers with low BRCA1 mRNA expression, no significant correlation was observed between the loss of PTEN expression and low BRCA1 mRNA expression in this unselected TN tumours panel. Our data suggest that, unlike the germinal context, PTEN and BRCA1 alterations in sporadic TN breast tumours are independent events.

Abstract P3-12-02: Loss of PTEN expression, PIK3CA mutations, and breast cancer survival in the Nurses’ health studies

Abstract Background: PTEN loss and/or PIK3CA mutation are hypothesized to predict more aggressive tumor behavior and worse outcomes in women with breast cancer. However, the results of previous studies with small sample size have been conflicting. Methods: We followed pre- and postmenopausal women with invasive breast cancer from the Nurses’ Health Study (diagnosed 1976-2011) and Nurses’ Health Study II (1989-2011) with data available on PTEN cytoplasmic expression (n=4316, breast cancer-specific deaths=777) and/or PIK3CA mutation (n=2930, breast cancer-specific deaths=317). PTEN protein expression was evaluated by immunohistochemistry and scored as a digitally quantified continuous measure (1-100%). Polymerase chain reaction and pyrosequencing of six hot spot mutations of PIK3CA were performed on DNA extracted from formalin-fixed paraffin-embedded tumors. Information on other covariates was self-reported at baseline and repeatedly measured with follow-up questionnaires every two to four years. Multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between loss of PTEN expression and/or PIK3CA mutation and breast cancer-specific mortality were estimated using Cox proportional hazards regression models. Results: In this large epidemiological study, the loss of tumor cell PTEN cytoplasmic staining expression (≤10%) occurred in 17.6% of cases, and the overall mutation of PIK3CA occurred in 10.8% of cases. After adjusting for tumor characteristics, treatment, and lifestyle factors, the loss of PTEN expression (versus expression &amp;gt;10%) was not associated with worse breast cancer survival among overall samples (HR =0.85; 95%CI=0.71-1.03) and among estrogen receptor (ER)-positive tumors (HR =1.11; 95%CI=0.84-1.47). However, among women with ER-negative tumors, PTEN expression loss was strongly associated with lower breast cancer mortality (HR =0.68; 95%CI=0.48-0.96). Overall mutation status of PIK3CA was not associated with breast cancer mortality (HR =1.06; 95%CI=0.78-1.45). Combining PTEN and PIK3CA status, compared with tumors without PTEN loss and without PIK3CA mutation (wild type), those with PTEN loss and/or PIK3CA mutation were not at higher risk (HR =1.05; 95%CI=0.85-1.32). However, women with PTEN loss and PIK3CA mutation jointly (n=39, breast cancer-specific deaths=15) had increased breast cancer mortality (HR =2.05; 95%CI=1.07-3.94). Conclusion: This study is the largest to date examining PTEN and PIK3CA status and breast cancer survival, in which we found that the prognostic value of PTEN status differed by ER status, and the joint status of PTEN loss of expression and PIK3CA mutation was associated with worse breast cancer survival. Citation Format: Tengteng Wang, Yujing J Heng, Gabrielle M Baker, Vanessa C Bret-Mounet, Susan E Hankinson, Michelle D Holmes, Wendy Y. Chen, Walter C. Willett, Bernard A. Rosner, Rulla M Tamimi, A. Heather Eliassen. Loss of PTEN expression, PIK3CA mutations, and breast cancer survival in the Nurses’ health studies [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-12-02.

Immunoexpression of PTEN, HER2/neu, and Ki-67 in endoscopic gastric carcinoma biopsies; their correlation with histological subtypes and one-year survival.

Gastric carcinoma is a major cause of cancer-related morbidity and mortality worldwide. Gastric neoplasms arise from genetic and epigenetic changes in various genes. Present study evaluates the immunoexpression of PTEN, HER2/neu, and Ki-67 in endoscopic gastric carcinoma biopsies and correlates the expression of these proteins with clinicopathological features. Adequate endoscopic biopsies of 27 cases of gastric carcinoma were evaluated for World Health Organization (WHO) and Lauren's classification subtypes along with HER2/neu, PTEN, and Ki-67 immunoexpression. HER2/neu immunostaining was scored as proposed in the Trastuzumab for gastric cancer (ToGA) trial while PTEN staining and downregulation were assessed using an immunoreactive score. The cut-off for Ki-67 expression was taken as 90th percentile of the values in adjacent non-neoplastic tissue. All statistical analysis was done at 5% level of significance with SPSS v22 statistical software. Tubular adenocarcinoma was the commonest WHO histological subtype and 56% of cases were of intestinal type as per Lauren's classification. 55.6% of cases showed a complete loss of PTEN expression in neoplastic tissue. 17 of the 19 cases with adjacent non-neoplastic tissue showed PTEN downregulation in neoplastic tissue. 81.5% of cases had a high Ki-67 index and HER2/neu overexpression was noted in 36% of cases. All the four cases who died had high Ki-67 proliferation indices; 3 patients had loss of PTEN expression and HER2/neu overexpression. We conclude that these immunomarkers can play important role in the behavior of gastric carcinomas and can be targeted for new therapies.