When you make a page the page for posts, it is no longer a page in the conventional sense, so it won’t load your custom page template. See the Template Hierarchy to learn how WordPress selects a template based on the requested page.
This behavior also extends to Conditional Tags. is_page() will return false on the page selected as page for posts, while is_home() will return true.
Rename your pages_news.php to home.php, no need to select it as the template (as we have seen, it is ignored anyway).