Evaluation of genetic diversity and population structure of Fragaria nilgerrensis using EST-SSR markers.

Fragaria nilgerrensis is a diploid wild strawberry widely distributed in Southwest China. Its white color and "peach-like" fragrance of fruits are valuable characters for the genetic improvement of cultivated strawberry plants. Its strong biotic and abiotic resistance and tolerance also enable it to survive in different habitats in the field. In this study, we evaluated the level of genetic variation within and between 16 populations with 169 individuals of F. nilgerrensis using 16 newly developed EST-SSR (expressed sequence tag-simple sequence repeats) markers. The results show that the genetic diversity of this species was high, based on Nei's genetic diversity (0.26) and polymorphic loci (0.41), although it is self-compatible and has clonal propagation. Significant genetic differentiation among populations was also detected by AMOVA analysis (Fst = 0.34), which could be indicative of little gene flow (Nm = 0.43) in F. nilgerrensis. The phylogenetic tree indicates that most of individuals from the same population have clustered together. These populations were not grouped based on the geographical distance, consistent with the Mantel test result (R2 = 0.0063, P > 0.05). All the populations were assigned into two ancestral groups, with some individuals admixed, suggesting ancestral gene flow had occurred between these two groups. Our developed EST-SSR markers as well as the genetic diversity and population structure analysis of F. nilgerrensis are important for genetic improvement in the breeding process. Moreover, the populations that contain high genetic diversity would be a priority for collection and conservation.

Identification of genetic alterations associated with primary resistance to EGFR-TKIs in advanced non-small-cell lung cancer patients with EGFR sensitive mutations.

BACKGROUND: Identification of activated epidermal growth factor receptor (EGFR) mutations and application of EGFR-tyrosine kinase inhibitors (EGFR-TKIs) have greatly changed the therapeutic strategies of non-small-cell lung cancer (NSCLC). However, the long-term efficacy of EGFR-TKI therapy is limited due to the development of drug resistance. The aim of this study was to investigate the correlation between the aberrant alterations of 8 driver genes and the primary resistance to EGFR-TKIs in advanced NSCLC patients with activated EGFR mutations. METHODS: We retrospectively reviewed the clinical data from 416 patients with stage III/IV or recurrent NSCLC who received an initial EGFR-TKI treatment, from April 2004 and March 2011, at the Sun Yat-sen University Cancer Center. Several genetic alterations associated with the efficacy of EGFR-TKIs, including the alterations in BIM, ALK, KRAS, PIK3CA, PTEN, MET, IGF1R, and ROS1, were detected by the routine clinical technologies. The progression-free survival (PFS) and overall survival (OS) were compared between different groups using Kaplan-Meier survival analysis with the log-rank test. A Cox regression model was used to estimate multivariable-adjusted hazard ratios (HRs) and their 95% confidence intervals (95% CIs) associated with the PFS and OS. RESULTS: Among the investigated patients, 169 NSCLC patients harbored EGFR-sensitive mutations. EGFR-mutant patients having PTEN deletion had a shorter PFS and OS than those with intact PTEN (P = 0.003 for PFS, and P = 0.034 for OS). In the combined molecular analysis of EGFR signaling pathway and resistance genes, we found that EGFR-mutant patients coexisted with aberrant alterations in EGFR signaling pathway and those having resistant genes had a statistically poorer PFS than those without such alterations (P < 0.001). A Cox proportional regression model determined that PTEN deletion (HR = 4.29,95% CI = 1.72-10.70) and low PTEN expression (HR = 1.96, 95% CI = 1.22-3.13), MET FISH + (HR = 2.83,95% CI = 1.37-5.86) were independent predictors for PFS in patients with EGFR-TKI treatment after adjustment for multiple factor. CONCLUSIONS: We determined that the coexistence of genetic alterations in cancer genes may explain primary resistance to EGFR-TKIs.