Q:

Is it possible to increase item size in Dynamo DB

After doing some research I found that the maximum size of an item (one row in a table) is 400 KB.  

Source of research:  http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Limits.html#limits-items

I wanted to insert a text data that contains over 1 MB of size.  This is basically one row worth of data. 
For example,
I have a table called users which contains summary of the user. 
The summary is a text field (String) and I want to insert data over 1 MB.  But Dynamo DB allows only 400 KB. 
Note 
I cannot store this in a file and keep a pointer

A:

You can not store more than 400 KB worth of data in one DynamoDB item (or record). 
This link, that you shared in your comment, requires you to break larger records into multiple items and handle merges in your application layer.  This isn't supported transparently by DynamoDB.