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Scientists in Spain, partly funded by Worldwide Cancer Research, have found a way to detect skin cancer spread (metastasis) before the process even happens. The researchers at the Spanish National Cancer Research Centre (CNIO) developed special bioluminescent mice, called ‘MetAlert’ mice, which ‘glow’ to show how the skin cancer cells prepare the surrounding areas prior to beginning to metastasise.

The team also identified a protein called MIDKINE which is involved in metastasis and discovered that switching this protein off could be a potential way to treat skin cancer. These game-changing findings were recently published in prestigious journal NATURE and you can watch a short animated video demonstrating the key findings here.

The importance of an early diagnosis

Early detection is essential when it comes to cancer. If a tumour is detected when it is small and still in one place, treatment has the best chance of success and patients have the greatest chance of survival. This is especially true for cuteanous melanoma, the most aggressive type of skin cancer. Even when it reaches a thickness of a little more than one millimetre, the tumour may begin to spread, sending cancer cells to other parts of the body to set up new tumours, in a process called metastasis. When this occurs, the prognosis for the patient is usually poor as it is much harder to find and kill all of the cancer cells. Whilst treatment options have improved for many other types of cancer, there are fewer available for melanoma and number of deaths remain very high.

Lead researcher Dr Marisol Soengas explains "Here we have been able to discover unknown mechanisms in the development of melanoma, and to identify new markers of metastasis that we have validated in samples from patients. These results open up new avenues for treatments."

MetAlert mice

One of the novelties of this paper is the development of the MetAlert mice that can reveal how melanoma acts throughout the body, even before the occurrence of new tumours (metastases). The team used genetic modifications to produce special mice that emit light (bioluminescence) when there is activation of the lymphatic vessels. "These bioluminescent mice are ideal for studying melanoma" says researcher Dr Sagrario Ortega, "because the generation of lymphatic vessels, known as lymphangiogenesis, is one of the initial steps in the spread of this cancer."

The MetAlert system can guide researchers when looking for genes and molecules involved in tumour progression at the very earliest stage. It also helps study cancer relapses after surgery, or monitor the response to anticancer drugs. To date, the techniques available to use in animals required probes or markers that had to be injected into the area around the tumour, or were based on the detection of tumour cells once they were already present in other organs, i.e. once metastasis had begun. As Dr David Olmeda, who performed most of the experiments says "one of the major complications in tracking melanomas has been precisely the lack of sensitivity of the standard techniques but with our MetAlert mice we think we have overcome this."

New mechanisms of cancer spread

Using MetAlert, researchers detected the mechanisms that melanomas activate early on to create their own pathways of spread. This spread is in part through the lymph vessels and lymphatic system and is at a much greater distance from the original tumour than they originally thought. The cells can also spread without many of the proteins that were previously considered essential to activate lymphangiogenesis in the tumour. "These results indicate a paradigm shift in the study of melanoma metastasis," says Dr Soengas.

The group next investigated proteins produced by aggressive and non-aggressive melanomas. “We found many proteins produced specifically by melanomas that act at a distance, but in this paper, we focused on one in particular, called MIDKINE, because it was new and could represent an alternative therapeutic target in the future," explains Dr Olmeda.

MIDKINE: A key to melanoma metastasis and a marker of aggressiveness

Again using the MetAlert mice, the group showed that MIDKINE plays an essential role in cancer spread, to the point that MIDKINE’s activation actually determines the tumour's ability to spread through the body.

Following the studies conducted on mice, the researchers showed how important MIDKINE would be in patients. They analysed the levels of MIDKINE in non-cancerous moles and in melanomas at different stages of development. This demonstrated that patients with high levels of MIDKINE in their lymph nodes have a worse prognosis and lower chance of survival. This finding could lead to the use of MIDKINE as a potential biomarker of aggressiveness.

The paper has further implications, because when MIDKINE is blocked, metastasis is also blocked, as the team discovered in animal models.

"In MIDKINE we have found a possible strategy that is worth considering for drug development", says Dr Soengas. "MIDKINE is not the only target, of course, but as melanoma is one of the cancers with the highest number of mutations described, finding a protein that can serve to block metastasis is an important step.

The researchers predict that the discovery of MIDKINE is only the beginning.

"These metastasis-visualisation techniques are opening up new avenues of research regarding new tumour mechanisms and other preclinical studies," say Dr Soengas, Dr Ortega, and Dr Olmeda, "and they are very useful because they can be adapted to various types of cancer, not only to melanoma.”

Dr Gwen Wathne, Research Impact Manager at Worldwide Cancer Research said: “This innovative research provides exactly the kind of answers that melanoma patients desperately need. With treatments few and far between for this aggressive cancer, discovering MIDKINE and its role in melanoma spread, means that researchers can begin to explore its use as a marker of melanoma aggressiveness, and how targeting MIDKINE could be used to prevent melanoma spreading before it even starts. And that’s incredible news. We need to be supporting more cutting edge, innovative research like this to give the best chance of survival to patients.

The work was supported by a grant from Worldwide Cancer Research, the Ministry of Economy, Industry and Competitiveness, the L’Oreal Paris USA–Melanoma Research Alliance, the Spanish Association Against Cancer, the Mutua Madrilena Foundation, the 'La Caixa' Foundation, Immutrain Marie Skłodowska-Curie ITN and projects of the US National Cancer Institute.

This text was adapted from a press release by the CNIO communications office in Spain.

Reference: Whole-body imaging of lymphovascular niches identifies pre-metastatic roles of midkine. David Olmeda, Daniela Cerezo-Wallis, Erica Riveiro- Falkenbach, Paula C. Pennacchi, Marta Contreras-Alcalde, Nuria Ibarz, Metehan Cifdaloz, Xavier Catena, Tonantzin G. Calvo, Estela Cañón, Direna Alonso, Javier Suarez, Lisa Osterloh, Chandrani Monda, Julie Di Martino, Osvaldo Graña, Francisca Mulero, Diego Megías, Marta Cañamero, David Lora, Inés Martinez-Corral, J. Javier Bravo Cordero, Javier Muñoz, Susana Puig, Pablo Ortiz-Romero, José L Rodriguez- Peralto, Sagrario Ortega, María S. Soengas (Nature 2017).