Proteins help in evaluating mouth cancer prognosis

Brazilian researchers have identified three markers that can help doctors predict the evolution of the illness and plan treatment.

By Karina Toledo

Agência FAPESP – One of the greatest difficulties faced by doctors dedicated to treating head and neck cancer is predicting the growth of epidermoid carcinoma tumors, such as the one diagnosed in the larynx of ex-President Luiz Inácio Lula da Silva in 2011. 

 

In a study published in December 2012 in the journal PLoS ONE, Brazilian researchers identified a protein—cofilin-1—that may serve as a biomarker for the level of aggressiveness of this type of tumor, which originates in the epithelial tissue.

 

The discovery may lead to the development of treatments aimed at reducing the  capacity of tumor cells to disseminate throughout the body.

 

“One would think that patients with extensive tumors would be those with the worst prognoses, but oftentimes, the evolution of the disease is better in these patients than in patients at early stages of the disease,” said Eloiza Tajara, professor at the São José do Rio Preto School of Medicine (Famerp) and coordinator of the FAPESP Thematic Project that led to the study. 

 

According to Tajara, the best available indicator of tumor aggressiveness  is the presence of tumor cells in the lymph nodes in the neck: “It is believed that a new tumor that is able to send cells to another part of the body is more aggressive than an extensive tumor that still has not metastasized. But the presence of lymph nodes negative for neoplastic cells is still no guarantee of a good prognosis.”  

 

Tajara affirmed that with more precise tools, doctors would be able to identify which patients needed invasive surgery in addition to chemotherapy and radiation therapy and which patients could be treated in a more conservative, less painful manner.

 

“Surgery in this region [the neck] can be mutilating and leave after-effects that affect the quality of life, such as difficulty in speaking, swallowing and chewing,” said Tajara.

 

In seeking markers for aggressiveness, the researcher’s team analyzed the proteins expressed in mouth epidermoid carcinoma samples, especially those from the tongue and the floor of the mouth (under the tongue), from 144 patients. 

 

“We separated the samples into two groups. The group considered to be more aggressive was composed of new tumors with lymph nodes that tested positive for the presence of cancer. The group considered to be less aggressive was composed of extensive tumors without positive lymph nodes. The results showed that these two types are considerably  different from a molecular point of view,” said Tajara. 

 

The researchers discovered over 100 proteins that were expressed differently between the two groups.. “The idea is to deeply investigate each of these proteins. But as the experiments take a long time, we decided to begin with cofilin-1, which is more highly expressed in aggressive tumors and, according to the scientific literature, participates in the cell migration process,” she said. 

 

Validation

 

The experiments to assess whether higher expression of cofilin-1 is related to a greater capacity for invasion by tumor cells were conducted under Tajara’s leadership by a post-doctoral researcher, Giovana Mussi Polachini, and with FAPESP funding. Andréia M. Leopoldino, a professor at the Universidade de São Paulo (USP) in Ribeirão Preto also participated in the study.

 

In epidermal carcinoma cell cultures, the expression of cofilin-1 was blocked using RNA interference. “Specific short interfering RNA molecules bind to cofilin-1 messenger RNA in the cell so that cofilin-1 protein can’t be synthesized,” explained Tajara.

 

In the body, the tumor cell manages to cross the epithelial basal membrane, which is the deepest one, and reach other tissues, enabling it to enter the blood and lymphatic circulation. To simulate the basal membrane in vitro, the scientists used a gelatinous protein mixture called Matrigel. Inhibiting the expression of cofilin-1 using RNA interference reduced the capacity of the tumor cells to cross this barrier. 

 

“Aside from being a marker for aggressiveness, this protein [cofilin-1] is a therapeutic target. A drug that is able to block its expression could impede the dissemination of tumor cells inside the organism and the spread of the disease,” affirmed Tajara. 

 

However, Tajara commented that cofilin-1 plays a very important signaling role in cells. Therefore, blocking its synthesis throughout the body could cause undesirable effects, and this possibility needs to be investigated. 

 

More markers
 

Another two markers related to the prognosis of patients with mouth tumors were recently reported in the journal PLoS ONE by researchers from the Head and Neck Genome Project (Gencapo) under the coordination of professor Adriana Madeira Álvares da Silva from the Universidade Federal do Espírito Santo.

 

The Gencapo consortium consists of researchers from several institutions who are dedicated to carrying out clinical, genetic and epidemiological studies on head and neck carcinoma and working on prevention of the disease. 

 

In the article, published in September 2012, the researchers showed that patients with increased levels of the HIF1α protein responded better to radiation therapy and showed higher survival rates. 

 

“The expression of this protein [HIF1α] is stimulated by a lack of oxygen. When the tumor grows rapidly, it becomes hypoxic [has inadequate oxygenation] and increases its synthesis of the protein, which stimulates the formation of new blood vessels to irrigate the region,” explained Tajara. 

 

Because radiation therapy produces toxic derivatives of oxygen, the increased vascularization facilitates the killing of tumor cells and helps to control the disease. 

 

In an article published in November 2012, the group analyzed the FGFR4 protein (which acts as a receptor the fibroblast growth factor) and found that when FGFR4 is expressed at lower levels and has a specific polymorphism (the amino acid arginine instead of the amino acid glycine), the patient runs a higher risk of disease recurrence and death. 

 

“FGFR4 is a protein that resides on the cell membrane and belongs to a family of receptors that binds to other proteins, setting off a cascade of signals inside the cell,” explained Tajara. 

 

However, it is still not known why this polymorphism in combination with the more limited expression of this protein correlates with a worse prognosis. “When an amino acid is substituted, the protein can present a very different structure and generate altered signals that affect cell behavior. But more studies are needed to better understand the polymorphism’s significance,” she said. 

 

“Proteomic Approaches Identify Members of Cofilin Pathway Involved in Oral Tumorigenesis” (doi: 10.1371/journal.pone.0050517), can be read at: www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0050517.

 

The article “HIF1-Alpha Expression Predicts Survival of Patients with Squamous Cell Carcinoma of the Oral Cavity” (doi: 10.1371/journal.pone.0045228), can be read at: www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0045228.

 

The article “FGFR4 Profile as a Prognostic Marker in Squamous Cell Carcinoma of the Mouth and Oropharynx” (doi: 10.1371/journal.pone.0050747), can be read at: www.plosone.org/article/info:doi/10.1371/journal.pone.0050747.