MoveTowards is not working with RectTransform component

Hello guys,

I am stuck with RectTransform component. I want to use Vector2.MoveTowards() function in my game. The problem is i am using RectTransform component. The same script is work with Transform component but it is not working with RectTransform component.

Here is my code

 using UnityEngine;
 using System.Collections;

 public class MoveSlider : MonoBehaviour {

 Vector2 start,target;
 public RectTransform slider;

     void Start(){
        start = new Vector2 (slider.anchoredPosition.x, slider.anchoredPosition.y);
        target = new Vector2 (slider.anchoredPosition.x-50f, slider.anchoredPosition.y-50f);
     }
     void Update(){
         slider.localPosition = Vector2.MoveTowards (start, target, Time.deltaTime);
     }
 }

In my above code I can print the start and target value in debug but I cant get a movement.

Do you have any idea why it is not working. here slider is my gameobject with RectTransform component in UI Canvas. the script is attach to camera and I am referencing slider to MoveSlider script.

Need any kind of help..