Shares of XM Satellite Radio Holdings Inc. climbed 12 percent last week after the Washington-based company said it crossed the 500,000 mark in subscribers to its satellite radio broadcast system.

XM Satellite, which predicts it will reach 1 million subscribers by the end of this year, also said two carmakers plan to offer its service in 2004 models. Acura is to include XM Satellite Radio as standard equipment in the Acura TL, and Audi is to offer it as an option in nine new models.

XM shares closed Thursday at $7.10 in an abbreviated holiday trading week, making it one of the biggest local gainers.

The Washington Post-Bloomberg regional stock index closed at 166.97, up 3.66 points. The NVTC Potomac Tech 60, an index made up of 60 local technology companies, closed at 535.75, up 15.83 for the week.

Atlantic Coast Airlines Holdings Inc. rose 18 percent after the Dulles-based regional carrier said it would cut 330 jobs as part of a plan to deal with the bankruptcy woes of its partner, United Airlines. Atlantic Coast, which runs United Express and Delta Connection flights, depends on United for much of its revenue.

The carrier said its first-quarter earnings, to be released Wednesday, would be 4 cents to 5 cents a share, lower than previously forecasted, because of delays in negotiating a new agreement with United on fees it receives to operate United Express service.

Atlantic Coast closed Thursday at $7.53 a share.

Shares of GenVec Inc. of Gaithersburg fell 21 percent after the money-losing biotechnology company agreed to buy specialty drugmaker Diacrin Inc. for $40.4 million in stock. The deal will fund GenVec's operations through 2006, increase manufacturing capability and give the biotech another experimental drug candidate, but it also will substantially dilute the value of existing shares.

GenVec closed at $1.16, making it one of the week's biggest local decliners.

Riggs National Corp. shares fell almost 6 percent to close last week at $13.50 even though the D.C.-based bank said first-quarter earnings rose substantially.