A growing tumour exerts considerable ongoing abnormal pressure on the healthy neighbouring cells. The CNRS/UPMC/Institut Curie team directed by Emmanuel Farge, Inserm Research Director at Institut Curie, has just discovered that this force can induce tumour gene expression. The physical stress induced by tumour growth might even trigger the initial phases of malignant transformation in the adjacent tissues. This major discovery is published in the 11 May 2015 issue of Nature.

While a tumour is actively growing, it gradually induces an abnormal and permanent pressure on the healthy neighbouring cells. Could this stress transform compressed healthy cells into tumour cells and affect the development of the tumour? This is the novel approach adopted by the Mechanics and Genetics of Embryonic and Tumoral Development[1] team led Emmanuel Farge, Inserm Research Director.

First, using experimental models, the researchers measured the pressure exerted by the growth of a colon tumour on the adjacent tissues. In doing so, they demonstrated that this mechanical stress activates the beta-catenin signalling pathway in the healthy tissues adjacent to the tumour, leading to the activation of tumour genes. “Beta-catenin is well known to activate tumorigenesis in many cancers,” notes Emmanuel Farge.

The mechanics of cancer: propagation strategies

Using magnets and healthy tissues loaded with magnetic liposomes, the team then mimicked the mechanical forces induced by a tumour in the surrounding tissues, and observed the consequences. “After two weeks of such mechanical stress, we observe an increase in phosphorylation (i.e. activation) of beta-catenin, together with its translocation to the cell nucleus,” observe the scientists. Under the effect of the stress, the beta-catenin protein detaches from the cell membrane to enter the nucleus, where it then activates oncogenes that promote tumour growth.

After a month, overexpression of the c-Myc oncogene, a target for beta-catenin, is then detected, which causes uncontrolled division of healthy cells, as well as overexpression of the target gene Zeb-1, which is responsible for the loss of cell adhesion that leads to invasiveness and metastasis.

After 2-3 months, aberrant crypt foci form in the colon (enlargement of the crypts and alteration of their structure), which corresponds to the initial steps in malignant transformation. “Activation by mechanical stress of the beta-catenin signalling pathway in the healthy tissues surrounding the tumour indicates a new way for a tumour to spread,” says Emmanuel Farge. “It creates an amplificatory autoregulation loop, a chain reaction, a real ‘domino effect:’ malignant changes mechanically induced by the tumour in the genetically healthy neighbouring cells cause abnormal growth of these cells, which itself applies abnormal stress to the as yet non-malignant neighbouring cells, and so on, in  a process likely to considerably amplify tumour growth and spread.”

In addition, it might contribute to tumour heterogeneity: the tumorigenic processes triggered in the adjacent cells might generate tumour cells with characteristics that are distinct from those at the core of the tumour and different in their type of response to treatment. This method of proliferation might thus constitute a factor in resistance to therapeutic treatments. 

Everything is therefore not purely biochemical in the development of colon cancer. Abnormal mechanical stresses, activating tumour biomolecules, thus appear to be a potential new engine for tumour progression and invasion.

This discovery reveals that mechanical stresses caused by growth of the tumour are likely to modify the healthy cells adjacent to it, activating the malignant transformations that boost its development.

A team of researchers from Inserm led by Paul Hofman (Inserm Unit 1081/University of Nice) has just made a significant advance in the area of early diagnosis of invasive cancers. In a study which has just been published in the journal Plos One, the team shows that it is possible to detect, in patients at risk of developing lung cancer, early signs, in the form of circulating cancer cells, several months, and in some cases several years, before the cancer becomes detectable by CT scanning. This warning could play a key role in early surgical intervention, thereby making it possible to attempt the early eradication of the primary cancer site.

© Fotolia

Studies carried out in animals have clearly shown that invasive tumours shed cancer cells into the bloodstream from the very earliest stages of their formation, even before the tumours are detectable by diagnostic imaging. The possibility of identifying these “sentinel” cells is considered a major asset in the race against time for the early detection, and hence treatment, of cancer. Circulating cancer cells are extremely rare in the bloodstream, are very heterogeneous and fragile, and are difficult to isolate without bias or loss.

The team of researchers led by Paul Hofman used a blood test developed during French research[1], which isolates all types of tumour cells from the bloodstream, without any loss, leaving them intact. The team studied a group of 245 people without cancer, including 168 patients at risk of later developing lung cancer because they had Chronic Obstructive Pulmonary Disease (COPD). Participants systematically underwent the blood test and standard diagnostic imaging tests. Using the blood test, circulating cancer cells were identified in 5 patients (3%), whereas imaging did not show any nodules in the lungs.

In these 5 patients, a nodule became detectable 1-4 years after detection of circulating cancer cells by the blood test. They immediately underwent surgery, and analysis of the nodule confirmed the diagnosis of lung cancer. Monitoring of the patients for a minimum of one year after surgery showed no sign of recurrence in the 5 patients, leading one to hope that the cancer had been eradicated. At the same time, no nodules were detected during monitoring of subjects who did not have circulating cancer cells, and no cancer cells were detected in the bloodstream of “control” subjects without COPD.

Detection of these circulating cells via this blood test could play a key role in early surgical intervention, thus making it possible to aim for early eradication of the primary cancer site.

Lung cancer is one of the most lethal cancers. According to the American Cancer Society (ACS), one-year survival among these patients is 44%, and 5-year survival only 16%. Only 15% of these cancers are presently diagnosed at a stage where the disease is localised. Early detection could both improve patient survival and help to improve health economics. COPD is the 3rd leading cause of deaths in the USA, and is mainly caused by smoking.

[1] known as ISET (Isolation by SizE of Tumour cells), and developed by Rarecells Diagnostics.

With approximately 42,000 estimated new cases in France in 2012, colon cancer is, for both sexes combined, the third most common type of cancer, and the second most common cause of cancer deaths after lung cancer. One of the challenges is to succeed in treating the cancer when metastases are present. Researchers at Institut Curie, Inserm and CNRS describe—theoretically and experimentally—in the journal Nature Communications, the combination of two genetic alterations responsible for tumour dissemination. As well as contributing knowledge on tumour progression, the cancer colon model thus developed offers the possibility of testing new therapies for eliminating metastases.

In order to better understand this long and extremely complex process, and to discover new therapeutic possibilities, it is crucial to elucidate all stages of tumour progression, from the initial mutation until the development of metastases.

From tumour to metastases, a multitude of events
© Eléonore Lamoglia/Institut Curie

A blend of theory and experiment
“With the help of a mathematical model compiling the data from over 200 scientific publications, we first identified two vital components in the epithelial-mesenchymal transition of intestinal cells,” explains Inna Kuperstein, a researcher from Emmanuel Barillot’s team. This transition converts the epithelial cells into a form known as mesenchymal[1]. These less specialised and more plastic cells lose their capacity to adhere to one another, and acquire properties that enable them to migrate and “blend” into their immediate environment. The epithelial-mesenchymal transition may represent the first step for tumour cells towards dissemination.

“For this to happen, our model shows that two events must occur in the intestinal cells: the Notch receptor must be activated, and the p53 gene must be lost,” comments Andrei Zinovyev, coordinator of the mathematical study at Institute Curie.

The researchers subsequently developed an animal model carrying these two alterations in the intestinal tissue. “This model makes it possible to study tumour cells throughout their development and thus better understand the modifications required for metastases to form,” explains Sylvie Robine, an Inserm Research Director at Institut Curie.

First observation: these mice developed numerous metastases, in several organs. The combination of alterations in Notch and p53 provides the starting ground needed for the development of metastatic colon cancer.

“When colon cancer cells begin to disseminate, they progressively lose the features of epithelial cells, the tissue from which they originate, to acquire the specific features of mesenchymal cells,” she continues.

In addition, the hallmarks of mesenchymal tissue are uniquely present in the cells of the invasive front of the tumour, cells that are moving towards the “exit” from the intestinal tissue (the stroma). The cells that escape from the original tissue are therefore cells that have begun the epithelio-mesenchymal transition. “This result has been corroborated by analysing samples from invasive colon cancers and metastases taken from patients,” states Prof. Daniel Louvard[2], CNRS Research Director at Institut Curie. “The cells present in these specimens have the characteristic features of mesenchyme, not of epithelia.”

Thanks to research carried out jointly by bioinformaticians from Emmanuel Barillot’s team and biologists from Prof. Daniel Louvard’s team, the stages in tumour progression and the various pathways leading to colon cancer are gradually yielding up their secrets.

“The combination of alterations in p53 and Notch creates the most conducive conditions for the development of metastases in colon cancers” explains Prof. Daniel Louvard.

The mice developed constitute an excellent preclinical model, and as such they may provide the basis of a search for new therapeutic targets. By knowing the specific alterations of the tumour from an individual, better targeted and more effective personalised treatments can be created.

French investigators have discovered new resistance mechanisms to targeted therapies used for less than three years in the treatment of melanoma. This discovery enables us not only to better understand why these treatments become ineffective but also to reveal new avenues for the management of these aggressive tumours. These studies have been published in the review Nature and have the benefit of an early on-line publication.

Investigators from the Predictive Biomarkers and new molecular strategies in anti-cancer therapy laboratory (Inserm/Gustave Roussy/Paris-Sud University) have shown that the mechanisms used by tumours to resist these treatments involves a protein complex called eIF4F which regulates the synthesis of proteins from RNA. 

Inserm/Dantchev, Dimitri

These results offer new prospects for the prediction of the efficacy of melanoma treatments using medicines targeting the BRAF protein.

Moreover, over the long term they may result in more effective new treatments emerging to treat not only this fearsome type of cancer, but also certain types of thyroid, colon, lung and brain cancers.

These studies have been conducted by Stéphan Vagner (Inserm U981/Gustave Roussy/Université Paris-Sud, Villejuif; Current address: CNRS UMR3348/Institut Curie, Orsay) and by Caroline Robert (Inserm U981/Gustave Roussy, Dermatology Department/Paris-Sud University, Villejuif) in collaboration with Laurent Désaubry (Therapeutic Innovation Laboratory, CNRS UMR 7200/University of Strasbourg, Illkirch).

The team of Drs Caroline Robert and Stéphan Vagner was supported by PAIR melanoma (Fondation ARC, The league Against Cancer and by INCa), Cancéropôle Ile de France and the group “Ensemble contre le mélanome” (Together against Cancer). This study has also benefited from the support of AAREC Filia Research, from the Wenner-Gren Foundation and from the Swedish Society of Medicine.

Treating hard and fast seems to be a good way to limit the side effects of radiotherapy. This is the discovery made by researchers at the Curie Institute, Inserm and the Vaud University Hospital, published in Science Translational Medicine on 16 July.
Radiotherapy remains one of the benchmark local treatments for cancer patients: increasingly accurate, it consists of irradiating cancer cells to destroy them while preserving neighbouring healthy tissues and organs as much as possible. By increasing the intensity of the irradiation 1,000 times over a very short time, the researchers have shown that the efficacy remains the same, but healthy tissues are better protected.

An effect for each mode of administration

In collaboration with Marie-Catherine Vozenin (Inserm and Vaud University Hospital, Lausanne, Switzerland), the radiobiologist Vincent Favaudon, eminent Inserm Research Director, studied the effects of radiotherapy on healthy and tumorous tissues depending on its mode of administration. “The Curie Institute laboratories on the Orsay site has an experimental electron linear accelerator that can deliver high radiation doses in a very short time, as a flash”, he explains. “To give an idea of scale, this accelerator delivers a radiation dose-rate 1,000 to 10,000 times more intense than conventional radiotherapy”.

The researchers wondered if this modified the effects on the tissues. “In our tumour models, a conventionally-administered 15 Gy dose to treat a lung tumour certainly leads to the occurrence of a pulmonary fibrosis between 8 weeks and 6 months after irradiation, while when using a ‘flash’ irradiation no fibrosis appears below 20 Gy”, explains the radiobiologist. This protective effect was also observed on apoptosis (programmed cell death produced following unrepaired damage to the DNA), blood capillaries and skin lesions.

“On the other hand, anti-tumour efficacy remained the same on all the tumour models we tested”, notes Marie-Catherine Vozenin, Inserm researcher and Head of the radiobiology laboratory in the Radio-oncology Department Vaud University Hospital. ‘Flash’ irradiation therefore protects healthy tissues very selectively from side effects arising.

“The equipment currently used in most radiotherapy departments, which operate using X-rays, is not efficient enough to generate the dose-rates needed for ‘flash’ irradiation. A major technological advance would be required to achieve it”, continues Vincent Favaudon. “However, the ‘Pencil Beam Scanning’ system currently being installed at the Curie Institute Protontherapy Centre will be capable of such performance and the medical team, assisted by the researchers, is planning to undertake a pre-clinical trial very quickly”.

Images of tissue sections

Effect of irradiation with 17 Gy administered on 0.28 s on healthy lung tissue, equivalent to a dose-rate of 60 Gy/s (middle picture) and in 548 s, equivalent to a dose-rate of 0.031 Gy/s (right picture). Tissue irradiated with a very high dose-rate looks the same as non-irradiated tissue, while tissue irradiated at low dose-rate is completely altered.

When tumour cells acquire the capacity to move around and invade other tissues, there is a risk of metastases and cancer treatment becomes more difficult. Carine Rossé, INSERM research fellow and Philippe Chavrier, Research Director at CNRS, working alongside Dr. Anne Vincent-Salomon, medical researcher at the Institut Curie, have recently discovered one of the mechanisms that allow triple negative breast cancer cells to exit the mammary gland. These results were published on-line by PNAS on 21^st April 2014.

Understanding how primary tumours infiltrate tissues and how certain cells detach and migrate to form metastases, is a major challenge in current cancer research. As such, the Institut Curie launched the incentive and cooperative research programme (PIC) “Breast Cancer: Invasion and Motility” in 2011 to give teams battling in this field access to important resources. Both programme coordinators Philippe Chavrier, Research Director at CNRS¹ and medical researcher² Anne Vincent-Salomon have joined forces in order to better understand how breast cancer cells move away and invade other tissues.

Furthermore, their latest discovery focuses on one of the most aggressive forms of cancer today – triple negative breast cancer. Dr. Anne Vincent-Salomon explains “this type of breast cancer is devoid of oestrogen and progesterone receptors with no overexpression of HER2. Women who have this type of cancer can neither benefit from hormonal therapy nor specific anti-HER2 therapy such as Herceptin”

A Tunnel in the Basement Membrane

Carine Rossé³ and Philippe Chavrier have discovered how these breast cancer cells break away from their original tissue. According to Philippe Chavrier “the tumour cells escape by digging a tunnel in the basement membrane that acts as a barrier around the mammary gland”.

His team has shown that the PKCλ protein and protease MT1-MMP are driving this cell “invasion”.  If PKCλ is “depleted” in stem cells derived from aggressive breast cancer, the supply of MT1-MMP to the cell surface is inhibited and cell invasion is no longer possible.

Thanks to the Biological Research Centre⁴ at the Institut Curie, who keep close to 60,000 tumour samples, researchers have also directly studied these proteins in tumour samples. “We have seen expressive correlation between both proteins associated with unfavourable prognosis in breast cancer” explains a researcher. “We have also identified a mechanism that allows both proteins work together to promote breast tumour cell invasion.”

Researchers have found an essential step in the quest for the early identification of highly invasive tumours, or even blocking the formation of metastases.

“We have identified some interesting potential therapeutic targets, but they remain to be validated” clarified a biologist. Drugs capable of halting these mechanisms will follow in time with the help of chemists.

Chain Reaction

Zoom-in of the inside of a cell is used to see the reactions between various proteins triggered by PKCλ. This latest protease MT1-MMP traffic “control” (red) enables the association of cortactin (green) with dynamin 2 (blue). This reaction sequence is necessary to allow the cell separate from its neighbours and invade other tissues.
© Carine Rossé – Philippe Chavrier/ Institut Curie