Vincenzo Eterno

Thyroid carcinoma is the most common endocrine malignancy and the first cause of death among endocrine cancers. We show that the tumorigenic capacity in thyroid cancer is confined in a small subpopulation of stem-like cells with high aldehyde dehydrogenase (ALDH(high)) activity and unlimited replication potential. ALDH(high) cells can be expanded indefinitely in vitro as tumor spheres, which retain the tumorigenic potential upon delivery in immunocompromised mice. Orthotopic injection of minute numbers of thyroid cancer stem cells recapitulates the behavior of the parental tumor, including the aggressive metastatic features of undifferentiated thyroid carcinomas, which are sustained by constitutive activation of cMet and Akt in thyroid cancer stem cells. The identification of tumorigenic and metastagenic thyroid cancer cells may provide unprecedented preclinical tools for development and preclinical validation of novel targeted therapies.

Mammary epithelial stem cells are fundamental to maintain tissue integrity. Cancer stem cells (CSCs) are implicated in both treatment resistance and disease relapse, and the molecular bases of their malignant properties are still poorly understood. Here we show that both normal stem cells and CSCs of the breast are controlled by the prolyl-isomerase Pin1. Mechanistically, following interaction with Pin1, Notch1 and Notch4, key regulators of cell fate, escape from proteasomal degradation by their major ubiquitin-ligase Fbxw7α. Functionally, we show that Fbxw7α acts as an essential negative regulator of breast CSCs' expansion by restraining Notch activity, but the establishment of a Notch/Pin1 active circuitry opposes this effect, thus promoting breast CSCs self-renewal, tumor growth and metastasis in vivo. In human breast cancers, despite Fbxw7α expression, high levels of Pin1 sustain Notch signaling, which correlates with poor prognosis. Suppression of Pin1 holds promise in reverting aggressive phenotypes, through CSC exhaustion as well as recovered drug sensitivity carrying relevant implications for therapy of breast cancers.

Colorectal cancer stem cells (CR-CSC) are responsible for the generation and maintenance of intestinal tumors and are highly resistant to conventional chemotherapeutic agents. Aurora-A, a serine-threonine kinase involved in mitosis regulation, plays multiple key functions in tumor initiation and progression. We found that Aurora-A is overexpressed in primary colorectal tumor cells, in the CR-CSC fraction, and in stem cell-derived differentiated cells, compared with normal colon tissue. Aurora-A expression was functionally linked to centrosome amplification in CR-CSC, as indicated by the decrease in cells with multiple centrosomes that followed Aurora-A silencing. Knockdown of Aurora-A resulted in growth inhibition of CR-CSC, alteration of cell cycle kinetics, and downregulation of the expression levels of antiapoptotic Bcl-2 family members, strongly sensitizing to chemotherapy-induced cell death. Moreover, Aurora-A silencing compromised the ability to form tumor xenografts in immunocompromised mice and reduced the migratory capacity of CR-CSC. Altogether, these results indicate that Aurora-A is essential for CR-CSC regeneration and resistance to cytotoxic stimuli and suggest that therapies directed against Aurora-A may effectively target the stem cell population in colorectal cancer.

// Vincenzo Eterno 1 , Alberto Zambelli 1,2 , Lorenzo Pavesi 1,2 , Laura Villani 4 , Vittorio Zanini 3 , Gianfranco Petrolo 3 , Stefania Manera 1 , Antonella Tuscano 1 , Angela Amato 1 1 Laboratory of Experimental Oncology and Pharmacogenomics, IRCCS Salvatore Maugeri Foundation, Pavia 2 Unit of Medical Oncology, IRCCS Salvatore Maugeri Foundation, Pavia 3 Breast Unit, IRCCS Salvatore Maugeri Foundation, Pavia 4 Unit of Pathology, IRCCS Salvatore Maugeri Foundation, Pavia. Correspondence: Angela Amato, email: // Keywords : Adipose-derived Mesenchymal Stem Cells (ASCs), Breast Cancer, HGF/c-Met crosstalk, Microenvironment, Neoangiogenesis. Received : September 05, 2013 Accepted : October 21, 2013 Published : October 23, 2013 Abstract Adipose tissue is a reservoir of Mesenchymal Stem Cells (Adipose-derived Mesenchymal Stem Cells, ASCs), endowed with regenerative properties. Fat graft was proposed for breast reconstruction in post-surgery cancer patients achieving good aesthetic results and tissues regeneration. However, recent findings highlight a potential tumorigenic role that ASCs may have in cancer recurrence, raising some concerns about their safety in clinical application. To address this issue, we established a model where autologous ASCs were combined with primary normal or cancer cells from breast of human donors, in order to evaluate potential effects of their interactions, in vitro and in vivo. Surprisingly, we found that ASCs are not tumorigenic per sè, as they are not able to induce a neoplastic transformation of normal mammary cells, however they could exhacerbate tumorigenic behaviour of c-Met-expressing breast cancer cells, creating an inflammatory microenvironment which sustained tumor growth and angiogenesis. Pharmacological c-Met inhibition showed that a HGF/c-Met crosstalk between ASCs and breast cancer cells enhanced tumor cells migration, acquiring a metastatic signature, and sustained tumor self-renewal. The master role of HGF/c-Met pathway in cancer recurrence was further confirmed by c-Met immunostaining in primary breast cancer from human donors, revealing a strong positivity in patients displaying a recurrent pathology after fat grafts and a weak/moderate staining in patients without signs of recurrence. Altogether our findings, for the first time, suggest c-Met expression, as predictive to evaluate risk of cancer recurrence after autologous fat graft in post-surgery breast cancer patients, increasing the safety of fat graft in clinical application.