Delta133P53Beta and Delta133P53Gamma isoforms are biomarkers of cancer stem cells

A method for predicting a risk of cancer metastasis in a subject suffering from cancer from a cancer sample of said subject and treating said subject, comprising:

• a) detecting sphere-forming cancer cells expressing Δ133p53β isoform, Δ133p53γ isoform, or both Δ133p53β and Δ133p53γ isoforms in said cancer sample;
• b) concluding to the presence of a significant risk of cancer metastasis in said subject if sphere-forming cancer cells expressing Δ133p53β isoform, Δ133p53γ isoform, or both Δ133p53β and Δ133p53γ isoforms are detected and to the absence of a significant risk of cancer metastasis in said subject if sphere-forming cancer cells expressing Δ133p53β isoform, Δ133p53γ isoform, or both Δ133p53β and Δ133p53γ isoforms are not detected;
• and
• c) treating said subject, wherein
• (i) if the subject is determined as being at a significant risk of cancer metastasis, an agent reducing Δ133p53β isoform, Δ133p53γ isoform, or both Δ133p53 and Δ133p53γ isoforms expression and an anticancer treatment is administered to the subject, or
• (ii) if the subject is determined as not being at a significant risk of cancer metastasis, an anticancer treatment is administered to the subject,
• wherein in step a) Δ133p53β isoform, Δ133p53γ isoform, or both Δ133p53 and Δ133p53γ isoforms are detected at nucleic acid level by measuring the amount of Δ133p53β isoform, Δ133p53γ isoform, or both Δ133p53β and Δ133p53γ isoforms mRNA or corresponding cDNA or at protein level,
• wherein the agent reducing Δ133p53β isoform, Δ133p53γ isoform, or both Δ133p53β and Δ133p53γ isoforms expression is antisense RNA or interfering RNA (iRNA).

A method for predicting a risk of cancer metastasis in a subject suffering from cancer from a cancer sample of said subject and treating said subject, comprising:

• a) detecting sphere-forming cancer cells expressing Δ133p53β isoform, Δ133p53γ isoform, or both Δ133p53β and Δ133p53γ isoforms in said cancer sample;
• b) concluding to the presence of a significant risk of cancer metastasis in said subject if sphere-forming cancer cells expressing Δ133p53β isoform, Δ133p53γ isoform, or both Δ133p53β and Δ133p53γ isoforms are detected and to the absence of a significant risk of cancer metastasis in said subject if sphere-forming cancer cells expressing Δ133p53β isoform, Δ133p53γ isoform, or both Δ133p53β and Δ133p53γ isoforms are not detected;
• and
• c) treating said subject, wherein
• (i) if the subject is determined as being at a significant risk of cancer metastasis, an agent reducing Δ133p53β isoform, Δ133p53γ isoform, or both Δ133p53 and Δ133p53γ isoforms expression and an anticancer treatment is administered to the subject, or
• (ii) if the subject is determined as not being at a significant risk of cancer metastasis, an anticancer treatment is administered to the subject,
• wherein the sphere-forming cancer cells expressing Δ133p53β isoform, Δ133p53γ isoform, or both Δ133p53β and Δ133p53γ isoforms in step a) are detected by performing an assay comprising the steps of:
• (i) resuspending cancer cells into a serum-free medium and plating them into tissue culture dishes, to which mammalian cells poorly adhere, at a seeding density between 250 and 2500 cells/cm2;
• (ii) incubating the cancer cells during 7 to 15 days after the resuspending and plating in step (i);
• (iii) counting spheres that are at least 50 μm large;
• and
• (iv) measuring the expression of Δ133p53β isoform, Δ133p53γ isoform, or both Δ133p53β and Δ133p53γ isoforms in the spheres that are at least 50 μm large,
• wherein the resuspending of cancer cells in step (i) is performed in the presence of specific growth factors EGF and bFGF;
• the incubating of step (ii) is performed at 37° C. under 5% CO2 atmosphere, and the counting in step (iii) is performed by a phase-contrast microscope.