Monday’s biggest gaining and declining stocks

SAN FRANCISCO (MarketWatch) � Shares of the following companies made notable moves in the U.S. stock market on Monday:

Career Education Co. CECO �shares traded up almost 9% after the Accrediting Council for Independent Colleges & Schools removed its show-cause directive on all 71 of the company�s campuses accredited by the agency. The directive related to the determination of job-placement rates.

GTSI Corp. GTSI �shares jumped 47% after the tech firm agreed to be acquired by a unit of Unicom Systems Inc. The deal price values the Herndon, Va., company at a 48% premium over GTSI shares� May 4 closing price of $5.24.

KT Corp.�s KT �U.S.-listed shares were up almost 8% after the South Korean telecommunications firm reported better-than-expected first-quarter results.

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NN Inc. NNBR �shares added 25.5% after the maker of high-precision metal bearing components reported a 7% increase in first-quarter profit and said it anticipates year-over-year earnings and margin improvement for 2012.

Vertex Pharmaceuticals VRTX �rallied more than 55% after the company announced favorable results in a Phase II study of a combination of two drugs evisioned as a treatment for cystic fibrosis.

Decliners

BroadSoft Inc. BSFT �fell almost 19% after the company said it expects adjusted second-quarter profit of 17 cents to 23 cents a share, below the estimate of 28 cents a share in a survey of analysts by FactSet Research.

Cognizant Technology Solution Corp. CTSH �sank more than 19% after the company trimmed its 2012 revenue target to at least $7.34 billion, below the Wall Street estimate of $7.55 billion.

DigitalGlobe Inc. DGI �fell 8.4% after it turned down a merger offer of $17 a share made by GeoEye Inc. GEOY ., which said it was disappointed by the move.

Georgia Gulf Corp. GGC �lost 6.7% after Westlake Chemical Corp. WLK �withdrew a buyout offer for the company. Georgia Gulf, a maker of building products, confirmed that the deal has been scuttled.

Lufkin Industries Inc. LUFK �shares dropped 5% after the company reported first-quarter results that came up short of most Wall Street forecasts.

PetMed Express Inc. PETS �shares shed 19.6% after the company reported a 4% decline in fourth quarter earnings on greater costs, though the results for the final three months of fiscal 2012 topped most estimates.

Thompson Creek Metals Co. TC �retreated 16% after the company reported a first-quarter loss on higher costs and decreased production.

TravelCenters of America LLC TA �shares moved down 15.4%, under pressure after the operator of roadside service facilities reported a first-quarter loss in line with most estimates. The stock had been up more than 40% before Monday�s selloff.