Subtract from previous row

Try this:

WITH cte1 AS 
(
    select   column1,
             rownum = row_number() OVER (ORDER BY (SELECT 0))
    from     table1 
)
SELECT column1,
case rownum
  when 1 then column1 else
column1 + 
(
  select sum(column1) from cte1 c2 where c2.rownum < c1.rownum
)
end
FROM    cte1 c1
WHERE   rownum > 0

What you describe here is called running total. It is a quite common discussion topic and there are several approaches. Yes, SQL 2012 itroduced some feature that are supportung such queries. I suggest you read this extensive article about the possibilities you might have, and their performance considerations:
http://sqlperformance.com/2012/07/t-sql-queries/running-totals[^]
LEAD and LAG are not for that, as they can be used to access the NEXT and PREVIOUS rows in your set, but you can't use them to accumulate, as your cumulation is not part of the set (see this article: http://www.bidn.com/blogs/KathiKellenberger/sql-server/3300/don-t-get-left-behind-learn-to-use-lag[^]).