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研究者在1月17日线上版科学(Science)期刊的一篇报告中，公布一种新的病毒，命名为默克细胞(Merkel cell)多瘤病毒(polyomavirus)，这是第一种和人类肿瘤强烈有关的病毒；多瘤病毒已知会引起动物的癌症，至于对人类的癌症发生的关联，即使有也还不清楚机转；虽然这项发现尚未证实多瘤病毒会引起皮肤的神经内分泌癌症—一般称为默克细胞癌(Merkel cell carcinoma)，但是提供了后续癌症治疗与预防选择的新线索。
默克细胞癌是罕见但侵犯快速的癌症，这种皮肤癌的发生率在过去20年增加3倍，每年约有1,500案例，常见于年长者和免疫功能不佳者，如AIDS或者服用免疫抑制药物者，发生恶性默克细胞癌的病患，约有半数活不到9个月。
资深作者，匹兹堡大学医学院的Patrick Moore医师在记者会中表示，如果这些发现获得确认，我们可以看看这个新病毒如何造成这个高致死率的恶性癌症，更重要的，用此模式了解癌症如何发生并且锁定细胞路径，我们获得的资讯可以朝向血液检测或者疫苗方向研究，改善疾病的治疗且有助于预防。
Moore医师和他的妻子也发现引起卡波西氏肉瘤（Kaposi's sarcoma）的原因，1993年时，这对夫妻发现卡波西氏肉瘤和疱疹病毒之间的关系，卡波西氏肉瘤常见于AIDS病患，也是非洲地区最常见的癌症。
在Medscape肿瘤学的访问中，Moore医师表示，他的团队对此最新发现感到惊讶；我们相当吃惊，我想任何人发现可能的致癌原因都会感到惊讶，后续还有许多研究要进行，但是默克细胞多瘤病毒会是相当好的线索。
【罕见癌症的可能原因】
同校的共同作者、Yuan Chang医师在记者会中表示，现在有一些疫苗可以预防癌症，例如人类乳突病毒与子宫颈癌；默克细胞多瘤病毒是另外一种可以增加我们对癌症的了解的模式，对于非病毒引起的癌症，如前列腺或乳癌，也可能会有重要意涵。
默克细胞多瘤病毒，一如人类乳突病毒，与肿瘤细胞基因图有关，与健康细胞基因图无关；这种关系摧毁了病毒的复制能力，而这可能就是致癌的第一步骤。
研究者使用数位转录体筛检(digital transcriptome subtraction)技术，共检视了将近400,000个传讯核醣核酸基因序列，来自默克细胞癌肿瘤组织的4个样本，他们和“人类基因体计划（Human Genome Project）”所绘出的基因序列图比较肿瘤基因图的基因序列，系统性地筛检已知的人类序列，以辨识可能来自外来物质的基因转录体。
他们发现1个序列类似但有别于已知的病毒，该团队发现这个序列属于一个新的多瘤病毒，在检测的10个默克细胞瘤里面有8个有出现，控制组中，59个身体不同部位的组织只有5个 (8%)、25个皮肤组织只有4 个(16%)有出现。
Moore 医师向Medscape肿瘤学表示，这是一种罕见的癌症，所以难以从单一个医学中心获得足够的组织样本进行大型研究；该团队计划继续搜集样本并且与其他机构合作。
即使默克细胞多瘤病毒被证实在神经内分泌癌症中扮演重要角色，但Chang医师认为，这个病毒可能只是其中的一小部分。
她在记者会中解释，现在我们需要厘清它如何作用，一旦病毒整合，它可能表现为致癌蛋白质，或者破坏会抑制肿瘤生长的基因；每种方法与结果都是引人注意的。
研究者宣称没有相关财金关系。
Science. 线上发表于2008年1月17日。
Newly Discovered Virus Linked to Neuroendocrine Cancer of the Skin
By Allison Gandey
Medscape Medical News
Researchers are unveiling a new virus in a report published online January 17 in Science. Dubbed the Merkel cell polyomavirus, it is the first to be strongly associated with a human tumor. Polyomaviruses have been shown to cause cancers in animals, but it is unclear what role, if any, they play in human cancer development. Although the important finding does not prove that the polyomavirus causes neuroendocrine cancer of the skin — also known as Merkel cell carcinoma — if confirmed, it might offer clues for future cancer treatment and prevention options.
Merkel cell carcinoma is a rare but extremely aggressive cancer that tends to spread rapidly. The incidence of this skin cancer has reportedly tripled over the past 20 years, to about 1500 cases a year. It tends to be seen in the elderly and in those with compromised immune systems, such as those with AIDS or patients taking transplant-related immunosuppressant drugs. About half of those with advanced Merkel cell carcinoma live 9 months or less.
"If these findings are confirmed, we can look at how this new virus contributes to a very bad cancer with high mortality and, just as important, use it as a model to understand how cancers occur and the cell pathways that are targeted," senior author Patrick Moore, MD, from the University of Pittsburgh School of Medicine, in Pennsylvania, said in a news release. "Information that we gain could possibly lead to a blood test or vaccine that improves disease management and aids in prevention."
Dr. Moore and his wife also discovered the cause of Kaposi's sarcoma. In 1993, the couple identified Kaposi's sarcoma–associated herpesvirus, the most common malignancy in AIDS patients and the most prevalent cancer in Africa.
During an interview with Medscape Oncology, Dr. Moore said his team was surprised by this latest finding. "We were certainly taken aback," he said. "I think anyone uncovering what could be a cause of cancer would be surprised by the finding," he laughed. A lot of work remains, but the Merkel cell polyomavirus might be an exciting clue.
Possible Cause of Rare Cancer Identified
Vaccines are now available against other causes of cancer, such as the human papillomavirus linked to cervical cancer. "The Merkel cell polyomavirus is another model that may increase our understanding of how cancers arise, with possibly important implications for nonviral cancers like prostate or breast cancer," coauthor Yuan Chang, MD, also from the University of Pittsburgh, pointed out in a news release.
Merkel cell polyomavirus, like the human papillomavirus, is said to integrate into the tumor cell genome, but not the genome of healthy cells. This integration destroys the virus's ability to replicate normally and might be the first step toward cancer.
Using a technique called digital transcriptome subtraction, the investigators looked at close to 400,000 messenger ribonucleic acid genetic sequences from 4 samples of Merkel cell carcinoma tumor tissue. They compared the sequences expressed by the tumor genome to gene sequences mapped by the Human Genome Project and systematically subtracted known human sequences to identify a group of genetic transcripts that might be from a foreign organism.
They found that 1 sequence was similar to, but distinct from, all known viruses. The team went on to show that this sequence belonged to a new polyomavirus present in 8 of 10 Merkel cell tumors they tested, but only 5 of 59 (8%) control tissues from various body sites and 4 of 25 (16%) control skin tissues.
"This is a rare cancer so it's hard to get enough tissue samples for large studies from just 1 center," Dr. Moore told Medscape Oncology. The group plans to continue collecting samples and will partner with others.
Even if the Merkel cell polyomavirus is proven to play a role in neuroendocrine cancer of the skin, Dr. Chang cautions that the virus is likely to be just part of a much larger picture.
"Now we need to find out how it works," she explained in a news release. "Once the virus integrates, it could express an oncoprotein, or it could knock out a gene that suppresses tumor growth. Either way, the results are bound to be interesting."
The researchers have disclosed no relevant financial relationships.
Science. Published online January 17, 2008.