You will probably need to instead set the label on to top of a different UIView:
UIView *labelBackground = [[UIView alloc] initWithFrame:self.label.frame];
self.label.backgroundColor = [UIColor clearColor];
self.label.frame = self.label.bounds;
CAGradientLayer *gradLayer=[CAGradientLayer layer];
gradLayer.frame = labelBackground.layer.bounds;
[gradLayer setColors:[NSArray arrayWithObjects:(id)([UIColor redColor].CGColor), (id)([UIColor cyanColor].CGColor),nil]];
gradLayer.endPoint=CGPointMake(1.0, 0.0);
[labelBackground.layer addSublayer:gradLayer];
[labelBackground addSubview:self.label];
[self.view addSubview:labelBackground];