Insight of endophytic fungi promoting the growth and development of woody plants

Microorganisms play an important role in plant growth and development. In particular, endophytic fungi is one of the important kinds of microorganisms and has a mutually beneficial symbiotic relationship with host plants. Endophytic fungi have many substantial benefits to host plants, especially for woody plants, such as accelerating plant growth, enhancing stress resistance, promoting nutrient absorption, resisting pathogens and etc. However, the effects of endophytic fungi on the growth and development of woody plants have not been systematically summarized. In this review, the functions of endophytic fungi for the growth and development of woody plants have been mainly reviewed, including regulating plant growth (e.g., flowering, root elongation, etc.) by producing nutrients and plant hormones, and improving plant disease, insect resistance and heavy metal resistance by producing secondary metabolites. In addition, the diversity of endophytic fungi could improve the ability of woody plants to adapt to adverse environment. The components produced by endophytic fungi have excellent potential for the growth and development of woody plants. This review has systematically discussed the potential regulation mechanism of endophytic fungi regulating the growth and development of woody plants, it would be of great significance for the development and utilization of endophytic fungi resource from woody plants for the protection of forest resources.

Abstract P2-09-34: An mRNA-based method to measure PI3K activity in cancer tissue using a computational pathway model to assess FOXO transcriptional activity

Introduction

The PI3K signaling pathway is frequently active in breast cancer, and therapeutic inhibitors have been developed. However, it has proven difficult to correctly predict treatment response. We developed a method that measures functional activity of the PI3K pathway using a computational model that infers transcriptional FOXO activity (downstream of PI3K) from expression levels of its target genes. In principle, PI3K pathway activity inhibits transcriptional FOXO activity, hence inactive FOXO is indicative of active PI3K.

Method

We developed a knowledge-based computational model to infer transcriptional FOXO activity from cancer tissue mRNA expression levels, using a Bayesian network approach (Verhaegh et al., Cancer Res 2014). Model calibration was done on microarray data from HUVEC cells with inducible FOXO3.A3-ER (GSE16573).

Results

The FOXO model was biologically validated with in-house microarray data from independent breast cancer cell lines. ER positive, PIK3CAE545K mutant MCF7 and triple negative MDA-MB-231 cells were stably transduced with a doxycycline inducible FOXO3.A3 expression vector, allowing controlled induction of FOXO3 protein activity. FOXO activity was determined to be low in untreated and 20% FBS treated MCF7 cells, and high after doxycycline, LY294002, and combination treatment.

Next, we tested our FOXO model on independent MCF7, BT-20 and MDA-MB-453 cell line data treated with EGFR inhibitor erlotinib (GSE30516), showing an increase of FOXO activity upon treatment, due to reduced PI3K pathway activity (combined Wilcox rank sum test p = 7.8x10−5).

We further analyzed independent publicly available data from breast cancer patients. FOXO was generally active in healthy breast tissue. Compared to healthy breast tissue, FOXO activity was higher in normal-like and luminal A breast cancer samples (p = 1.9x10−6 and 0.025, resp.), and lower in luminal B samples (p = 4.2x10−7).

In addition to the above mechanism for regulating FOXO activity, literature suggests that FOXO can also be activated by cellular oxidative stress, which is often associated with PI3K signaling. This may be assessed using expression levels of the FOXO target gene SOD2, which is differentially expressed between the two FOXO activity modes, and whose function is to reduce oxidative stress. Public data shows an increasing percentage of elevated SOD2 levels among FOXO-active samples with increasing breast cancer aggressiveness: 7% in normal-like, 5% in luminal A, 18% in luminal B, 31% in HER2-enriched and 74% in basal like breast cancer.

Conclusion

Our computational model to measure PI3K activity using FOXO target gene mRNA levels was able to measure increased FOXO activity in multiple cancer cell lines after PI3K inhibition. FOXO activity was measured high in healthy breast tissue and in normal-like and luminal A breast cancer, and lower in luminal B, indicating PI3K activity in the latter group. In more aggressive subtypes, FOXO activity was increasingly accompanied by high SOD2 expression, suggesting oxidative stress with associated PI3K activity as the FOXO activating mechanism.

Clinical utility for improved response prediction and monitoring of PI3K pathway inhibitors is being investigated with clinical partners.

Citation Format: Verhaegh W, van Ooijen H, Hornsveld M, Dam C, Eijkelenboom A, Dou M, Velter R, Burgering B, van de Stolpe A. An mRNA-based method to measure PI3K activity in cancer tissue using a computational pathway model to assess FOXO transcriptional activity [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-09-34.

Thawed human hepatocytes in primary culture

In drug metabolism studies, isolated and cultured human hepatocytes provide a useful model for overcoming the difficulty of extrapolating from animal data. In vitro studies with human hepatocytes are scarce because of the lack of livers and suitable methods of storage. After developing a new method for cryopreservation of human hepatocytes, we evaluated the effects of deep freezing storage on their viability, morphology, and functional and toxicological capabilities in classical culture conditions. Freshly isolated human hepatocytes were cryopreserved in medium containing 10% Me2SO and 20% fetal calf serum, using a Nicool ST20 programmable freezer (-1.9 degrees C/min for 18 min and -30 degrees C/min for 4 min). Cells were stored in liquid nitrogen. Viability of thawed human hepatocytes was 50-65% as assessed by erythrosin exclusion test prior to purification on a Percoll density gradient. Morphological criteria showed that thawed human hepatocytes require an adaptation period to the medium after seeding. Functional assessments showed that human hepatocytes which survive freezing and thawing preserve their protein synthesis capabilities and are able to secrete a specific protein, anionic peptidic fraction, which is involved in the hepatic uptake of bile-destined cholesterol. We then studied Midazolam biotransformation to test metabolic functions, and erythromycin toxicity by Neutral Red test (cell viability) and 3-(4,5-dimethylthiazol-2-yl)-diphenyl tetrazolium bromide test (cell metabolism). All of these experiments indicated that thawed human hepatocytes should be used 38 h after seeding for optimum recovery of their functions: membrane integrity, protein synthesis, and stabilization of drug metabolism enzymes.