The Saxons open their title defence against the United States, who are coached by former Ireland boss Eddie O'Sullivan, at Franklin's Gardens.
Some players will view the coming fortnight as an opportunity to force their way into Martin Johnson's World Cup plans, but Lancaster insists winning the competition for a sixth time is the key objective.
"This is a fantastic occasion. The last time the tournament was played, England had a squad of 44 touring Australia and New Zealand," he said.
"All the focus was on them and rightly so. But this year there isn't any rugby being played now and the tournament is in England.
"We have a responsibility to the fans and country to perform well.
"At the same time the players will be putting themselves in the shop window for the World Cup.
"But most important of all is that we win this tournament.
"When you get into tournament mode you want to try and win it. We won it last year and we want to retain it."
The Saxons have been drawn in Pool A alongside the USA and Tonga with the winners meeting either Canada, Italy 'A' or Russia on finals day on June 18.
Lancaster is unsure what to expect from tournament debutants Tonga.
"We've played the USA a few times and we're looking forward to that again, but Tonga are a bit of an unknown," he said.
"From watching them at the World Cup in 2007 I expect them to be a major threat.
"We don't know too much about them but we'll have a chance to see them against the USA before we play them."
Matt Stevens returns to England colours for the first time since serving his two-year ban for cocaine use in his preferred position of tighthead prop.
Stevens is joined in the Saxons line-up by Saracens team-mate Mouritz Botha, a week after lifting the Aviva Premiership title with victory over Leicester at Twickenham.
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