Intraspecific phylogeny of a Patagonian fescue: differentiation at molecular markers and morphological traits suggests hybridization at peripheral populations

BACKGROUND AND AIMS

Grasses of the Festuca genus have complex phylogenetic relations due to morphological similarities among species and interspecific hybridization processes. Within Patagonian fescues, information concerning phylogenetic relationships is very scarce. In Festuca pallescens, a widely distributed species, the high phenotypic variability and the occurrence of interspecific hybridization preclude a clear identification of the populations. Given the relevance of natural rangelands for livestock production and their high degradation due to climate change, conservation actions are needed and knowledge about genetic variation is required.

METHODS

To unravel the intraspecific phylogenetic relations and to detect genetic differences, we studied 21 populations of the species along its natural geographical distribution by coupling both molecular [internal transcribed spacer (ITS) and trnL-F markers] and morpho-anatomical analyses. Bayesian inference, maximum likelihood and maximum parsimony methods were applied to assemble a phylogenetic tree, including other native species. The morphological data set was analysed by discriminant and cluster analyses.

KEY RESULTS

The combined information of the Bayesian tree (ITS marker), the geographical distribution of haplotype variants (trnL-F marker) and the morpho-anatomical traits, distinguished populations located at the margins of the distribution. Some of the variants detected were shared with other sympatric species of fescues.

CONCLUSIONS

These results suggest the occurrence of hybridization processes between species of the genus at peripheral sites characterized by suboptimal conditions, which might be key to the survival of these populations.

Abstract P3-08-24: Mutational characterization of HER2-positive breast cancer

Background: Studies of mutational analysis have been widely reported in various global series of breast cancer. However, in the era of different phenotypes of breast cancer, these analyses should be more specific in order to find differences in each phenotype that could predict response to treatment. Particularly HER2 positive is a special subtype with different connotations that make the analysis of its genotype very interesting.

Methods: Cohorts of 47 consecutive samples of HER2 positive breast cancer, treated in our institution were analyzed. It was conducted a mutational study with NGS technique of the most common genes involved in breast cancer.

Results: 10 patients were metastatic at diagnostic, 17 with negative estrogen receptor expression, the median value of Ki67 was 45 (20-95) and the median initial tumor size was 33.5 mm (18-111). Inmunohistochemical expression of HER2 was +3 in 31 tumors and +2 in 15 with a median ratio by FISH of 3,2 (1,18-8,3). We also analyzed the expression of HER by PCR of mRNA in 35 samples with a median expression of 2,49 (0,26-33,15). 38 patients underwent surgical excision of the tumor with a pathologic complete response observed in 19.

We found a total of 38 significant mutations and the genes with more frequent mutations were MCPH1 (100%), HNF1 (98%), p53 (96%), somatic BRCA1 (62%), TSC1 (30%), PIK3CA (23%), ATM (21%), ALK (15%) and somatic BRCA2 (13%). Although the aim of the study was to find the most frequent mutations in this subtype, we have also analyzed possible correlations of those with pathological response or with more common variables, finding no significance in any of them.

Conclusions: In our series, we found a high percentage of mutations in MCPH1, HNF1 and p53 genes with almost 100% of mutations in p53 that are also limited in a very specific area. Also interesting is the 62% of mutations found in BRCA1 and 13% in BRCA2 that could allow more specific treatments in this subgroup. Although the study did not have the power to assess the predictive factor of these mutations, it is very suggestive that in the 7 patients with BRCA mutations, 6 achieved a complete pathological response.

Citation Format: Velasco Sánchez A, Gasol Cudos A, Morales S, Veas Rodriguez J, Serrate López A, Mele Olivé J, Canosa Morales C. Mutational characterization of HER2-positive breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-08-24.

Abstract P3-10-17: mRNA expression of HER2 by PCR as a strong predictor of pathologic response to neoadjuvant antiHER2 therapy

Background: Pathologic response to neoadjuvant therapy is the most important prognostic factor so new agents should aim to improve it. HER2 expression in breast cancer provides prognostic and predictive information of response to antiHER2 therapy. The quantification of HER2 expression by mRNA is one of the most potent markers of cellular dependence to HER2 pathway.

Methods: From a series of 160 patients with early or locally advanced HER2 positive breast cancer who received neoadjuvant treatment with chemotherapy and antiHER2 drugs, mRNA expression of HER2 was analyzed in 69 specimens and it was correlated to pathologic complete response (pCR).

Results: Median age was of 52.5 years (29-86), tumor size of 33mm (10-111), 39 (53%) patients had nodal involvement. Median ki67 expression was of 45% (17-80), 28 (38%) tumors were estrogen receptor (ER) positive and 46 (62%) negative. We also analyze the expression of tumor-infiltrating-lymphocytes (TILs) by immunohistochemistry in 43 samples because their expression is also a strong predictive of pathologic response. A total of 31/69 patients (45%) achieved a pCR with a median of mRNA expression of 7,55 (3,8 – 11) in comparison with 2.03 (1,2 -2,8) in patients without pCR (p: 0,002). In the univariable analysis, variables correlated to pCR were estrogen receptor=0 (OR 0,186 IC 95% 0,063-0,549, p: 0,002), mRNA (OR 5,689 IC 95% 1,854-17,452, p: 0,002) and TILs (OR 15,167 IC 95% 3,223-71,38, p: 0,001) and in the multivariable analysis, TILs and mRNA expression were found to be independent predictive factors for pCR. The quantification of HER2 by mRNA obtained an impressive response specially in ER negative patients with a rate of pCR of 100% in samples of mRNA expression upper of 3,6 and ER negative. However, patients with mRNA expression lower than 3,6 with a pCR rate of 32%, could reach to an 80% rate if they had high TILs expression.

Conclusions: Quantification of HER2 expression by mRNA is a strong predictive factor of pCR (OR 5,689); achieving a 100% pCR in ER negative tumors. TILs are also a predictive factor for pCR (OR 15,167) and its combination with mRNA expression could improve pCR rates; thus, patients with mRNA expression lower than 3,6, if they had a higher TILs expression could reach to an 80% pCR.

Citation Format: Gasol Cudós A, Morales Murillo S, Veas Rodriguez J, Velasco Sánchez A, Serrate López A, Melé Olivé J, Canosa Morales C. mRNA expression of HER2 by PCR as a strong predictor of pathologic response to neoadjuvant antiHER2 therapy [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-10-17.

Does nitric oxide play a role in maternal tolerance towards the foetus?

In pregnancy there occurs maternal tolerance to the foetus. Several mechanisms have been proposed to explain this phenomenon. The main immune population in the decidua are macrophages and natural killer cells, but with some "special" suppressor characteristics. There is also a predominant TH2 response. The non classical MCH type I HLA-G is expressed by trophoblasts and can suppress lymphomononuclear cytotoxicity. Other system to avoid the immune system is the expression of indoleamine-2,3-dioxygenase, that suppresses T cell activation by degrading tryptophan. Even though in the placenta there is a high production of nitric oxide, a well-known immune modulator, low attention has been paid to its role in maternal tolerance. There are many data showing that NO affects the IDO, CD95/CD95-L and the balance between TH1/TH2. Maybe NO could interact with several mechanisms at the same time, which could modify the tolerogenic activity depending on the concentration and the presence of other factors in the medium.