T-cells In Skin Can Kill Melanoma Cells And Prolong Survival

T-cells residing in the skin, namely the memory T-cells could provide effective and longterm immunity against melanoma, according to a team of scientists at Dartmouth's Norris Cotton Cancer Center.

Reason for the Study

The research team led by Mary Jo Turk, PhD, wanted to find the reason behind why vitiligo occurring in melanoma improved the prognosis, with such patients surviving much longer and some even achieving complete remission.

There have been published studies that have clearly shown that persons with vitiligo have a 3 times reduced risk of developing melanoma which appeared in The British journal of dermatology. 168(1):162-71, Jan 2013 H E Teulings; M Overkamp et al;

Methods and Findings of the Study

Employing a mouse model of skin cancer and vitiligo, the research team were able to show that T-cells in the skin which attacked normal pigmented cells (melanocytes) in vitiligo were also able to attack and mount an immune response against cancerous melanocytes in melanoma i.e. the target of the immune T-cell was the melanocyte in both cases.

The current study thus demonstrated that T-cells found in the skin are also more than capable of killing melanoma cells and providing effective and longterm immunity against future tumors too.

The findings of the current study have challenged the long held notion that immune T-cells that provide immunity against cancers are present only in lymphoid tissues such as lymph nodes and spleen, and when activated, reach the tumor cell site via the bloodstream.

"Our studies challenge this long-held belief by showing that tumor-killing T cells already reside in skin, where they can rapidly respond and kill melanoma cells" said Turk.

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What is Vitiligo?

Vitiligo is a skin condition where depigmented white patches occur on the skin in various parts of the body.

It is believed that vitiligo is an autoimmune disease where a person’s immune T-cells mistakenly perceive the pigmented cells in the skin (melanocytes) as foreign, and attack and destroy them. Destruction of pigment producing cells therefore leads to depigmented patches forming in various parts of the body.

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Genetic Basis For Inverse Association Between Vitiligo And Melanoma

In addition to the immunity against melanoma provided by the cytotoxic T-cells in vitiligo, there is a genetic basis for this inverse relationship.

Studies have shown that the TYR gene allele which is a risk factor for development of vitiligo confers protection against melanoma and vice versa.

An original article to this effect appeared in the New England Journal of Medicine by Ying Jin et al - N Engl J Med 2010; 362:1686-1697May 6, 2010DOI: 10.1056/NEJMoa0908547 titled ‘Variant of TYR and Autoimmunity Susceptibility Loci in Generalized Vitiligo’.

Plans for Future Research

Future research plans to validate the findings of the current study include

• Looking for the presence of  immune T-cells in the skin of human patients
• To look for these T-cells in other organs such as lungs where melanoma is known to spread.
• Based on the current findings, future research for skin cancer therapy could be based on the generation of such T-cells

We can conclude with the words of the lead author, "While we have shown that these T cells can kill melanoma in skin, we still need to determine whether they exist in other organs such as lung, where metastatic melanoma grows.  Since our study identifies that resident memory T cells are critical for protection against tumors, and that T cells in skin provide long-term immunity to melanoma, the generation of such cells should be the goal of future cancer therapies."

References:

1. Fast Facts: An Easy-to-Read Series of Publications for the Public - (https://www.niams.nih.gov/health_info/vitiligo/vitiligo_ff.asp#b)
2. Is there any known anticorrelation between cancer and autoimmunity? - (https://www.researchgate.net/post/Is_there_any_known_anticorrelation_between_cancer_and_autoimmunity)

Source-Medindia