Endometrial cancer cells exhibit high expression of p110β and its selective inhibition induces variable responses on PI3K signaling, cell survival and proliferation

Targeting Class I-II-III PI3Ks in Cancer Therapy: Recent Advances in Tumor Biology and Preclinical Research

Phosphatidylinositol-3-kinase (PI3K) enzymes, producing signaling phosphoinositides at plasma and intracellular membranes, are key in intracellular signaling and vesicular trafficking pathways. PI3K is a family of eight enzymes divided into three classes with various functions in physiology and largely deregulated in cancer. Here, we will review the recent evidence obtained during the last 5 years on the roles of PI3K class I, II and III isoforms in tumor biology and on the anti-tumoral action of PI3K inhibitors in preclinical cancer models. The dependency of tumors to PI3K isoforms is dictated by both genetics and context (e.g., the microenvironment). The understanding of class II/III isoforms in cancer development and progression remains scarce. Nonetheless, the limited available data are consistent and reveal that there is an interdependency between the pathways controlled by all PI3K class members in their role to promote cancer cell proliferation, survival, growth, migration and metabolism. It is unknown whether this feature contributes to partial treatment failure with isoform-selective PI3K inhibitors. Hence, a better understanding of class II/III functions to efficiently inhibit their positive and negative interactions with class I PI3Ks is needed. This research will provide the proof-of-concept to develop combination treatment strategies targeting several PI3K isoforms simultaneously.

Bone Marrow Mesenchymal Stem Cells (BMSCs) Enhance the In Vitro Activities of Endometrial Cells via Strengthening the Phosphorylation and Activation of Phosphoinositide 3-Kinase (PI3K)

Mancozeb (ethylene bis-dithiocarbamate) is an organometallic fungicide and is widely used in agriculture and is related to women’s spontaneous abortion and menstrual abnormalities. Bone marrow mesenchymal stem cells (BMSCs) can impede endometrial fibrosis via suppressing PI3K pathway, but its effect on the activity of endometrial cells induced by mancozeb/EDU is unclear. This study intends to explore the protective effects of co-culture with BMSCs on endometrial cells after mancozeb/EDU treatment. Endometrial cells were randomized into control group, mancozeb/EDU group (mancozeb/EDU treatment), BMSCs group (cells were co-cultured with BMSCs after mancozeb/EDU treatment), and inhibitor group (treated with PI3K-Akt-mTOR inhibitor) followed by analysis of the expression of PI3K-Akt-mTOR pathway-related proteins, cell viability by MTT and cell invasion and migration by Transwell and scratch test. Mancozeb/EDU treatment significantly inhibited PI3K-Akt-mTOR signals and cell proliferation, increased apoptosis and decreased cell invasion and migration, which were all reversed by co-culture with BMSCs. Additionally, the co-culture with BMSCs modulated the In Vitro viability of endometrial cells by influencing PI3K-Akt-mTOR signal transduction pathway, which can be inverted by PI3K-Akt-mTOR pathway-specific antagonists. In conclusion, BMSCs exerted a protective effect on the In Vitro viability of endometrial cells by manipulating the PI3K/Akt/mTOR signal transduction, which helped to protect endometrial cells from damage caused by mancozeb/ETU treatment.

The role of different PI3K protein subtypes in the metastasis, angiogenesis and clinical prognosis of hepatocellular carcinoma

BACKGROUND AND OBJECTIVES

Abnormal activation of the PI3K/AKT pathway is closely related to tumor occurrence, development and angiogenesis. PI3K, as a key protein in the PI3K/Akt pathway, has different subtypes that play diverse roles in various tumors. The aim of this study was to examine the roles of different PI3K protein subtypes (PI3Kp110α, PI3Kp110β, and PI3Kp110δ) in the metastasis, angiogenesis and prognosis of hepatocellular carcinoma (HCC).

METHODS

The roles of different PI3K protein subtypes in the metastasis, angiogenesis and prognosis of HCC were assessed by immunohistochemical staining of 97 HCC tissues and the STRING database.

RESULTS

Our results showed that PI3Kp110α and PI3Kp110δ were associated with HCC metastasis and angiogenesis. Patients with high expression of PI3Kp110α and PI3Kp110δ had a worse prognosis and shorter survival time, respectively, than those with low expression, whereas these effects were not observed for PI3Kp110β. Cox regression analysis showed that PI3Kp110α and clinical stage were independent risk factors for the overall survival of HCC patients.

CONCLUSIONS

PI3Kp110α and PI3Kp110δ promoted HCC metastasis and angiogenesis via the PI3K/AKT pathway, and PI3Kp110α was an independent risk factor for HCC patients. These findings provide valuable insights for the prognosis evaluation and the selection of subtype inhibitors of HCC patients.

Evaluation of Hsp90 and mTOR inhibitors as potential drugs for the treatment of TSC1/TSC2 deficient cancer

Inactivating mutations in either TSC1 or TSC2 cause Tuberous Sclerosis Complex, an autosomal dominant disorder, characterized by multi-system tumor and hamartoma development. Mutation and loss of function of TSC1 and/or TSC2 also occur in a variety of sporadic cancers, and rapamycin and related drugs show highly variable treatment benefit in patients with such cancers. The TSC1 and TSC2 proteins function in a complex that inhibits mTORC1, a key regulator of cell growth, which acts to enhance anabolic biosynthetic pathways. In this study, we identified and validated five cancer cell lines with TSC1 or TSC2 mutations and performed a kinase inhibitor drug screen with 197 compounds. The five cell lines were sensitive to several mTOR inhibitors, and cell cycle kinase and HSP90 kinase inhibitors. The IC50 for Torin1 and INK128, both mTOR kinase inhibitors, was significantly increased in three TSC2 null cell lines in which TSC2 expression was restored. Rapamycin was significantly more effective than either INK128 or ganetespib (an HSP90 inhibitor) in reducing the growth of TSC2 null SNU-398 cells in a xenograft model. Combination ganetespib-rapamycin showed no significant enhancement of growth suppression over rapamycin. Hence, although HSP90 inhibitors show strong inhibition of TSC1/TSC2 null cell line growth in vitro, ganetespib showed little benefit at standard dosage in vivo. In contrast, rapamycin which showed very modest growth inhibition in vitro was the best agent for in vivo treatment, but did not cause tumor regression, only growth delay.

PP2A and E3 ubiquitin ligase deficiencies: Seminal biological drivers in endometrial cancer

OBJECTIVE

PI3K-AKT pathway mutations initiate a kinase cascade that characterizes endometrial cancer (EC). As kinases seldom cause oncogenic transformation without dysregulation of antagonistic phosphatases, pivotal interactions governing this pathway were explored and correlated with clinical outcomes.

METHODS

After exclusion of patients with POLE mutations from The Cancer Genome Atlas EC cohort with endometrioid or serous EC, the study population was 209 patients with DNA sequencing, quantitative gene-specific RNA expression, copy number variation (CNV), and surveillance data available. Extracted data were annotated and integrated.

RESULTS

A PIK3CA, PTEN, or PIK3R1 mutant (-mu) was present in 83% of patients; 57% harbored more than 1 mutation without adversely impacting progression-free survival (PFS) (P = .10). PIK3CA CNV of at least 1.1 (CNV high [-H]) was detected in 26% and linked to TP53-mu and CIP2A expression (P < .001) but was not associated with PFS (P = .24). PIK3CA expression was significantly different between those with CIP2A-H and CIP2A low (-L) expression (the endogenous inhibitor of protein phosphatase 2A [PP2A]), when stratified by PIK3CA mutational status or by PIK3CA CNV-H and CNV-L (all P < .01). CIP2A-H or PPP2R1A-mu mitigates PP2A kinase dephosphorylation, and FBXW7-mu nullifies E3 ubiquitin ligase (E3UL) oncoprotein degradation. CIP2A-H and PPP2R1A-mu (PP2A impairment) and FBXW7-mu (E3UL impairment) were associated with compromised PFS (P < .001) and were prognostically discriminatory for PIK3CA-mu and PIK3CA CNV-H tumors (P < .001). Among documented recurrences, 84% were associated with impaired PP2A (75%) and/or E3UL (20%).

CONCLUSION

PP2A and E3UL deficiencies are seminal biological drivers in EC independent of PIK3CA-mu, PTEN-mu, and PIK3R1-mu and PIK3CA CNV.

Nuclear upregulation of class I phosphoinositide 3-kinase p110β correlates with high 47S rRNA levels in cancer cells

The class I phosphoinositide 3-kinase (PI3K) catalytic subunits p110α and p110β are ubiquitously expressed but differently targeted in tumours. In cancer, PIK3CB (encoding p110β) is seldom mutated compared with PIK3CA (encoding p110α) but can contribute to tumorigenesis in certain PTEN-deficient tumours. The underlying molecular mechanisms are, however, unclear. We have previously reported that p110β is highly expressed in endometrial cancer (EC) cell lines and at the mRNA level in primary patient tumours. Here, we show that p110β protein levels are high in both the cytoplasmic and nuclear compartments in EC cells. Moreover, high nuclear:cytoplasmic staining ratios were detected in high-grade primary tumours. High levels of phosphatidylinositol (3,4,5)-trisphosphate [PtdIns(3,4,5)P ₃] were measured in the nucleus of EC cells, and pharmacological and genetic approaches showed that its production was partly dependent upon p110β activity. Using immunofluorescence staining, p110β and PtdIns(3,4,5)P ₃ were localised in the nucleolus, which correlated with high levels of 47S pre-rRNA. p110β inhibition led to a decrease in both 47S rRNA levels and cell proliferation. In conclusion, these results present a nucleolar role for p110β that may contribute to tumorigenesis in EC.This article has an associated First Person interview with Fatemeh Mazloumi Gavgani, joint first author of the paper.

PI3Kβ-A Versatile Transducer for GPCR, RTK, and Small GTPase Signaling

The phosphoinositide 3-kinase (PI3K) family includes eight distinct catalytic subunits and seven regulatory subunits. Only two PI3Ks are directly regulated downstream from G protein-coupled receptors (GPCRs): the class I enzymes PI3Kβ and PI3Kγ. Both enzymes produce phosphatidylinositol 3,4,5-trisposphate in vivo and are regulated by both heterotrimeric G proteins and small GTPases from the Ras or Rho families. However, PI3Kβ is also regulated by direct interactions with receptor tyrosine kinases (RTKs) and their tyrosine phosphorylated substrates, and similar to the class II and III PI3Ks, it binds activated Rab5. The unusually complex regulation of PI3Kβ by small and trimeric G proteins and RTKs leads to a rich landscape of signaling responses at the cellular and organismic levels. This review focuses first on the regulation of PI3Kβ activity in vitro and in cells, and then summarizes the biology of PI3Kβ signaling in distinct tissues and in human disease.

Class I Phosphoinositide 3-Kinase PIK3CA/p110α and PIK3CB/p110β Isoforms in Endometrial Cancer

The phosphoinositide 3-kinase (PI3K) signalling pathway is highly dysregulated in cancer, leading to elevated PI3K signalling and altered cellular processes that contribute to tumour development. The pathway is normally orchestrated by class I PI3K enzymes and negatively regulated by the phosphatase and tensin homologue, PTEN. Endometrial carcinomas harbour frequent alterations in components of the pathway, including changes in gene copy number and mutations, in particular in the oncogene PIK3CA, the gene encoding the PI3K catalytic subunit p110α, and the tumour suppressor PTEN. PIK3CB, encoding the other ubiquitously expressed class I isoform p110β, is less frequently altered but the few mutations identified to date are oncogenic. This isoform has received more research interest in recent years, particularly since PTEN-deficient tumours were found to be reliant on p110β activity to sustain transformation. In this review, we describe the current understanding of the common and distinct biochemical properties of the p110α and p110β isoforms, summarise their mutations and highlight how they are targeted in clinical trials in endometrial cancer.

[Clinical Significance and Mechanism of PI3K p110β Overexpression in Non-small Cell Lung Cancer]

BACKGROUND

Phosphatidylinositide 3-kinases (PI3K) pathway is one of the most important pathway in cells, which plays an important role in proliferation, growth, differentiation and mobility of cells. The aberrant activation of PI3K pathway was exsited in 50%-70% cases of non-small cell lung cancer (NSCLC). As the key point in PI3K pathway, expression of PI3K plays a critical role in activity of the pathway, which is closely related with the initiation and development of NSCLC, furthermore with the response of tumor to target treatment. Our study is to analyze the clinical significance and mechanism of PI3K p110β overexpression in NSCLC.

METHODS

Expression of p110β and other proteins in PI3K pathway were detected by immunohistochemistry in 170 cases of NSCLC. Correlation between expression of p110β and clinicopathological characteristics of patients as well as expression of other proteins in PI3K pathway was analyzed.

RESULTS

In 170 NSCLC, overexpression of p110β was found in 41.8% of cases. Correlation between overexpression of p110β and Ki 67 index was significant (P=0.040). No significant difference of p110 expression were observed among different cohorts of gender, age, smoking status, classification, grade and stage (P>0.05). Correlation between expression of p110β and other proteins in PI3K pathway was various, positively correlated with PTEN loss (P<0.001) and negatively correlated with mutant EGFR (P=0.022), while not correlated with P-Akt (Ser473), HER2, ALK, ROS1 and wild type EGFR (P>0.05).

CONCLUSIONS

Overexpression of p110β is frequently detected in NSCLC. It is closely related with PTEN loss NSCLC, which shows that it plays an important role in maintaining and developing of tumors driven by PTEN loss. It initiates the proliferation of tumor cells in NSCLC without phosphorylating Akt. PIK3CB mutation is not the major cause of overexpression of p110β. Dysregulation of receptor tyrosine kinases (RTKs) doesn't show potential of increasing p110β level in cancer tissue, furthermore the expression of p110β in tumors with EGFR mutation is lower than in tumors without EGFR mutation.

PIK3CA mutations confer resistance to first-line chemotherapy in colorectal cancer

Chemotherapy represents an important treatment option for colorectal cancer (CRC), but only half of the patients benefit from these regimens. We explored the potential predicting value and mechanism of PIK3CA mutation in CRC chemotherapy. CRC specimens from 440 patients were retrospectively collected and examined with a fluorescence PCR-based method. The correlation of first-line chemotherapy response and PIK3CA mutation was evaluated according to follow-up and medical records. The underlying mechanism of PIK3CA mutation in chemotherapy resistance was assessed with CRC tumors and primary cells. The mutation frequency of the PIK3CA gene in CRC patients was 9.55%, which was correlated with late TNM staging and lower histological grade. The CRC patients with PIK3A mutation showed worse response to first-line chemotherapy than those without PIK3CA mutation. PIK3A mutation tumor cells showed poor sensitivity to first-line chemotherapy in vitro and in vivo. PIK3CA mutation induced PI3K/Akt signaling activation to increase LGR5⁺ CRC stem cells survival and proliferation, from which lead to chemotherapy resistance. Furthermore, PIK3CA^mutation/LGR5⁺ expression was an independent detrimental factor for CRC patients. Our findings indicated that PIK3CA mutation induced PI3K/Akt activation contributed to CRC stem cells survival and proliferation, from which cells further resistance to chemotherapy. PIK3CA ^mutation/LGR5⁺ expression was a potential biomarker for monitoring chemotherapy resistance in CRC.

Linking type 2 diabetes and gynecological cancer: an introductory overview

Type 2 diabetes (T2D) is a chronic disease with a growing prevalence and a leading cause of death in many countries. Several epidemiological studies observed an association between T2D and increased risk of many types of cancer, such as gynecologic neoplasms (endometrial, cervical, ovarian and vulvar cancer). Insulin resistance, chronic inflammation and high free ovarian steroid hormones are considered the possible mechanisms behind this complex relationship. A higher risk of endometrial cancer was observed in T2D, even though this association largely attenuated after adjusting for obesity. A clear relationship between the incidence of cervical cancer (CC) and T2D has still not be determined; however T2D might have an impact on prognosis in patients with CC. To date, studies on the association between T2D and ovarian cancer (OC) are limited. The effect of pre-existing diabetes on cancer-specific mortality has been evaluated in several studies, with less clear results. Other epidemiological and experimental studies focused on the potential role of diabetes medications, mainly metformin, in cancer development in women. The correct understanding of the link between T2D and gynecologic cancer risk and mortality is currently imperative to possibly modify screening and diagnostic-therapeutic protocols in the future.