US STOCKS-Wall St lower as investors turn cautious; Apple drags
* Apple biggest drag on S&P 500, Nasdaq after Nikkei report
* Gilead up after hep B drug found safe
* First Solar up after Goldman upgrades stock to buy
* Crude slips amid Chinese economy worries
* Indexes down: Dow 0.51 pct, S&P 0.28 pct, Nasdaq 0.47 pct (Updates to early afternoon)
By Abhiram Nandakumar
Jan 5 (Reuters) - Apple dragged Wall Street lower on Tuesday, cutting short a feeble recovery from a bruising selloff on the first trading day of the year.
A fall in crude oil prices and a stronger dollar also contributed to the shaky start to the year, which was triggered by weak Chinese economic data on Monday.
In a bid to stabilize its markets, the People's Bank of China on Tuesday injected $20 billion into the financial system. Continuación...