The chokeberry grows in the eastern USA in swamps and wetlands.
According to the new research, it could be given as a "nutraceutical" - a pill made from its extract - to enhance treatment.
The laboratory research, reported in the Journal of Clinical Pathology, showed that cancer cells died after 48 hours of exposure to the berry extract.
Researchers also found the berry had no impact on normal blood vessels.
Researchers at Southampton University, UK, and King's College Hospital, London, UK, worked together on the project.
Researcher Bashir Lwaleed said he believed the findings were "very exciting."
He said: "The low doses of the extract greatly boosted the effectiveness of gemcitabine, when the two were combined. In addition, we found that lower doses of the conventional drug were needed, suggesting either that the compounds work together synergistically, or that the extract exerts a "supra-additive" effect.
"This could change the way we deal with hard to treat cancers in the future."
Cytotoxicity of gemcitabine enhanced by polphenolics from Aronia melanocarpa in pancreatic cancer cell line AsPC-1. Journal of Clinical Pathology 18 September 2014; doi:10.1136/jclinpath-2013-202075 [abstract]
According to Roger Taylor, who helped found Dr Foster Intelligence, the problems lies with national clinical audits.
These have "conflicts of interest," he claims in the Health Service Journal, leading to them failing to expose the extent of variation in consultants' performance.
Out of ten national clinical audits used for consultant data, just one identified individuals whose performance was exceptionally good or bad - making them outliers, he said.
As an example, he said using death rates was not the best way to measure outcomes for hip and knee operations.
He said: “If you select an outcome such as complication rates or revision rates, you are much more likely to see real differences.”
He added: "There are real conflicts of interest… If you have a group of surgeons who are trying to agree a way of comparing themselves… the analysis that is going to most likely satisfy a large number of people and get consensus is the one that shows they’re all the same.”
Professor Ben Bridgewater, a cardiac surgeon who leads the project for the Healthcare Quality Improvement Partnership, rejected the allegations - but agreed there should be further refinement of indicators.
He said: “Certainly - the ones I’m involved with - all the stuff is out in the public domain so the idea that these are purely professional society led audits that are looking after their membership just isn’t the situation at all.”
But some patients may be getting dramatic results from the services, widely touted as a remedy for mental health problems.
The latest figures show the results of 920,000 referrals in the year ending in March.
These showed that 37% of patients - or 37% - failed to take up the offer of therapy or gave up waiting.
But 364,000 finished a course and 60% of these showed reliable improvement.
In 20,000 instances patients ceased taking psychotropic medicines during treatment.
The Health and Social Care Information Centre figures show big differences around England in access to services.
About 60% of patients get their first appointment within a month of referral - but in one area this is just 3% and in another area it is 96%.
Centre chair Kingsley Manning said: “Today’s report provides a new dimension of understanding to this important area of care.
"Depression and anxiety are known to affect a broad spectrum of people within our society – and today’s figures point to almost two thirds of referrals for Psychological Therapy being for women."
Experts called for a "wider review" after announcing proposals for the National Institute for Health and Care Excellence.
NICE has been in conflict with the government over the introduction of new cancer drugs - leading to the Cancer Drugs Fund being managed by NHS England.
Yesterday it called for a new agreement with NHS England and the Department of Health on how to pay for new treatments such as cancer drugs and those for rare conditions.
It promised to set up its own office for innovation, offering a "flight path" for companies wanting to introduce products into the NHS.
But it also called for "more productive" sharing of risk between companies and NHS - reflecting its frustration at the high prices charged for new drugs.
Its call for a new agreement suggests further frustration that its efforts to drive down drug prices might be undermined by the Cancer Drugs Fund.
NICE said its won consultation on the topic had found "no agreement" on what should be done.
Chief executive Andrew Dillon said: "It’s clear that just changing NICE’s methods will not overcome concerns about how the NHS accesses new treatments.
“We also need to look at other processes, including the model of pharmaceutical research and development, the expectations that companies and patient groups have about how risk and reward is shared between the industry and a publicly funded NHS, and in the arrangements for commissioning expensive new treatments.
"And it’s essential that industry also recognises its role in making innovative treatments available to people at a fair price.”
* Today NICE approved a melanoma drug after manufacturers agreed a discount on its published prices for the NHS. The size of the discount is to be kept a commercial secret.