* U.S. Q4 economic growth revised slightly lower

* Bumble slumps after downbeat quarterly revenue forecast

* UnitedHealth drops after report of antitrust probe

* Indexes down: Dow 0.26%, S&P 0.17%, Nasdaq 0.47%

NEW YORK, Feb 28 (Reuters) -

U.S. stocks fell modestly on Wednesday, a day ahead of a key inflation reading that could heavily shape expectations for the timing of an interest rate cut from the Federal Reserve.

The personal consumption expenditures (PCE) price index, the Fed's preferred inflation gauge, is expected to show prices ticked 0.3% higher on a monthly basis in January.

Stocks have struggled to retain upward momentum in recent days leading up to the data after a lengthy rally that peaked last week, fueled by enthusiasm around the potential for artificial intelligence (AI) after Nvidia reported quarterly earnings.

Evidence of stubborn inflation in recent data on consumer and producer prices, a resilient U.S. economy, and commentary from some Fed officials have caused the market to

dial back expectations

for the Fed's first cut to June from March.

"Now that those earnings catalysts are behind us in the rearview mirror there could be some softness as now the market has to get its arms around the inflation trajectory and the Federal Reserve's reaction, whether it's with rhetoric or a higher-for-longer policy," said Keith Buchanan, senior portfolio manager at GLOBALT Investments in Atlanta.

"Any embers or symptoms of resurgence in pockets, or in aggregate, of inflation will definitely be taken pretty harshly by the markets."

The Dow Jones Industrial Average fell 99.67 points, or 0.26%, to 38,872.74, the S&P 500 lost 8.50 points, or 0.17%, at 5,069.64 and the Nasdaq Composite dropped 75.97 points, or 0.47%, to 15,959.33.

Data on Wednesday confirmed the U.S. economy grew at a solid clip in the fourth quarter on strong consumer spending but it appears to have lost some speed early in 2024.

In addition to the PCE data, reports for weekly initial jobless claims and manufacturing activity are due this week and will also help gauge the strength of the economy and path of interest rates.

Boston Fed Bank President Susan Collins said on Wednesday the Fed should be "taking time" to assess data before making any change to policy in order to be sure to deliver on both of the central bank's mandates of maximum employment and price stability.

In addition, New York Federal Reserve President John Williams said that even as there is

still some distance

to cover in achieving the Fed's 2% inflation target, the door is opening to rate cuts this year depending on how the data come in.

UnitedHealth fell 4.93% as the biggest drag on the Dow and second largest on the S&P 500 after a report on Tuesday said the U.S. Department of Justice has launched an antitrust investigation into the healthcare conglomerate.

Semiconductor equipment supplier Applied Materials lost 2.74% following a subpoena from the U.S. Securities and Exchange Commission in February.

Beyond Meat surged 39.89% as the plant-based meat maker placed its bets on price hikes and steep cost cuts to turn around its battered margins, triggering a squeeze on its highly shorted shares.

Major cryptocurrency firm Coinbase Global rose 2.03% and peer Marathon Digital climbed 2.54% as bitcoin surged past $61,000.

Declining issues outnumbered advancers by a 1.03-to-1 ratio on the NYSE while on the Nasdaq, declining issues outnumbered advancers by about a 1.52-to-1 ratio.

The S&P 500 posted 63 new 52-week highs and one new low while the Nasdaq recorded 166 new highs and 79 new lows.

(Reporting by Chuck Mikolajczak; Editing by Richard Chang)