President Trump's promise of a highly anticipated tax-cut plan gave the markets enough fuel to sustain small weekly gains late Friday. The S&P 500 was up 0.85% for the week, and the Dow Jones Industrial Average rose by a lesser 0.46%. The news wasn't a complete surprise, as Treasury Secretary Steven Mnuchin said a mere day prior that Trump's tax plan would be released shortly. In other news, there were plenty of companies making big moves or big headlines in the markets this week. Here are some highlights.

This stock is soaring

It's been a dreamlike month for investors of Straight Path Communications Inc. (NYSEMKT: STRP), which has soared 205% in April after the news that AT&T (NYSE:T) agreed to acquire it earlier this month -- but the development became even more intriguing this week, when another bidder was said to be considering a bid of its own.

Wall St. street sign with American flag hanging in the background.

Image source: Getty Images.

On April 10, AT&T announced that it would acquire Straight Path in hopes of boosting its development of 5G technology and infrastructure. Straight Path has developed a nationwide portfolio of millimeter-wave spectrum, which is hugely important to AT&T in the increasingly competitive wireless market. AT&T agreed to pay $95.63 per share, for a total value of about $1.6 billion, including liabilities.

In the most recent development, Straight Path revealed in a regulatory filing that an unnamed third party -- which, according to sources talking to Reuters, is likely to be Verizon -- was considering a competitive offer that's expected to exceed AT&T's price. We'll see how this shakes out for investors, but chances are this is at, or perhaps even above, a fair premium for the company. It also shows just how important and valuable companies with a portfolio of 5G technology are becoming, and savvy investors should keep that in mind.

Better than bad

Shares of GNC Holdings (NYSE:GNC) also had a good week, after surging around 20% during intra-day trading on Tuesday. The driving force behind the move higher, you ask? It was simply a better-than-expected first-quarter earnings report, which still included a revenue decline.

Before we get to the details of GNC's first quarter, it's important to put this week's roughly 13% gain in perspective -- because it's been a really rough few years for investors.

GNC Chart

GNC data by YCharts

GNC's revenue declined 3.6% to $644.8 million during the first quarter. Despite the decline, that was about $17 million better than analysts had estimated. Adjusted earnings per share checked in at $0.37, much lower than the prior year's $0.69 but still $0.03 better than analysts' expectations.

Slightly worse than GNC's total revenue decline was its comparable-store sales, which dropped 3.9% -- although that, too, was better than the fourth quarter's far worse 8.6% decline in comparable-store sales. GNC's average transaction declined by more than 12% during the first quarter, and sales at fell by 7.2%.

Ultimately, if investors want to sum up GNC's first quarter, it's fair to say it was better than very dismal expectations. And the stock's 13% gain this week pales in comparison with the value the stock has shed over the past couple of years. Management has some work to do if it wants to turn the business around.

The value of plastic

Last but not least, shares of American Express Company (NYSE:AXP) jumped higher on Thursday, after investors were impressed with first-quarter earnings. The company's earnings per share of $1.34, while down 8% compared with the prior year, topped analysts' estimates calling for $1.28 per share. Excluding the company's Costco-related business, as well as foreign exchange rates, its adjusted revenue net of interest expense grew 7%, in part because card-carrying consumers are spending more.

"The last couple of years have been an important transition period, and we've entered 2017 stronger, more focused, and more resilient," said Kenneth I. Chenault, chairman and chief executive officer, in a press release. "There is still work to do, but our underlying performance this quarter gives me added confidence in our ability to deliver our 2017 EPS outlook of $5.60-$5.80 and position American Express for sustainable growth in the years ahead."  

American Express is difficult to figure out currently. It has a premium brand image and generates strong profits, but it's recently been cutting costs. American Express cut marketing and promotional spending by 4% over the past 12 months, according to, at a time when competition is increasing.

American Express has a strong business and brand, but the future of mobile payments and increasing competition from other credit cards make beating the market for its investors far from a guarantee.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.