One of the current greatest challenges for translational cancer research is to understand how to switch a cold tumor (immune refractory) into hot tumor (immune responsive). We previously reported that inactivation of DNA MMR leads to MSI status and generates hypermutated cancers with increased number of neoantigens (Germano et al). A large proportion of MSI tumors display long-lasting responses when challenged with immune modulators (Le et al Science). We also reported that treatment of mouse and human CRC cells with temozolomide (TMZ) leads to MMR deficiency, increasing tumor mutational burden (TMB) and response to immune checkpoint blockades (Germano et al). These preclinical data led to design ARETHUSA, a proof-of-concept two steps clinical trial (Crisafulli et al). During the first step the TMZ treatment was used both with curative intent and to trigger an hypermutation status in MSS mCRC patients. In the second step the anti PD-1 agent pembrolizumab was deployed only if patients develop a TMB > 20 mut/Mb upon progression to TMZ. Furthermore, in patients receiving a prolonged treatment of TMZ, alterations in MMR emerged.  Interestingly, we found that a subset of the patients whose tumors displayed the acquisition of MMR deficiency and increased TMB, achieved disease stabilization upon pembrolizumab treatment Fig. X (Crisafulli et al).

Graphical description of the ARETHUSA trial. The mutational signature and TMB evaluation were represented for TMZ treated patients. (Created with BioRender.com)

Overall, we provide evidence that the inactivation of genes involved in DNA repair can be achieved pharmacologically with TMZ treatment, while offering potential clinical benefit to mCRC patients refractory to immune based treatments.

MMRd tumors with impaired antigen presenting machinery respond to immune checkpoint blockade

Tumors may evade immune control mainly owing to alterations in the antigen presenting machinery (APM). Several studies have reported that molecular defects in the major complex of histocompatibility I (MHC I) and in the protein B2M (that is key for the cell surface expression of MHC class I) represent possible mechanisms of acquired resistance to immune checkpoint blockade in melanoma and lung tumors (Amodio et al).  We functionally evaluated the impact of B2M loss in immune evasion and resistance to immune checkpoint blockades in colorectal, pancreatic and breast cancer murine cell lines. Although the antigen presentation was compromised, the growth of MMR deficient (MMRd) murine cell lines was severely impaired by the administration of immune checkpoint blockades.

(Created with BioRender.com)

MMR deficient tumors respond to anti PD-1 despite the antigen presenting machinery is compromised.

Although the APC was compromised, we provide evidence that patients bearing MMRd cancers other than colorectal may receive benefit from immune checkpoint blockades. The analysis of tumor microenvironment revealed that CD4+ T cells were pivotal in establishing an effective cancer immune response but only in the context of MMRd tumors. Overall, these data highlight the role of tumor associated effector CD4+ T cells in pre-clinical models and patients with impaired APM.

Publications

• Sogari A, Rovera E, Grasso G, Mariella E, Reilly NM, Lamba S, Mauri G, Durinikova E, Vitiello PP, Lorenzato A, Avolio M, Piumatti E, Bonoldi E, Aquilano MC, Arena S, Sartore-Bianchi A, Siena S, Trusolino L, Donalisio M, Russo M, Di Nicolantonio F, Lembo D, Bardelli A.
  Tolerance to colibactin correlates with homologous recombination proficiency and resistance to irinotecan in colorectal cancer cells
  Cell Rep Med. 2024 Feb 20;5(2):101376
• Rospo G, Chilà R, Matafora V, Basso V, Lamba S, Bartolini A, Bachi A, Di Nicolantonio F, Mondino A, Germano G, Bardelli A.
  Non-canonical antigens are the largest fraction of peptides presented by MHC class I in mismatch repair deficient murine colorectal cancer
  Genome Med. 2024 Jan 19;16(1):15.
• Di Nicolantonio F, Bardelli A
  Precision oncology for KRASG12C-mutant colorectal cancer.
  Nat Rev Clin Oncol. 2023 Jun;20(6):355-356
• Amodio V, Lamba S, Chilà R, Cattaneo CM, Mussolin B, Corti G, Rospo G, Berrino E, Tripodo C, Pisati F, Bartolini A, Aquilano MC, Marsoni S, Mauri G, Marchiò C, Abrignani S, Di Nicolantonio F, Germano G, Bardelli A.
  Genetic and pharmacological modulation of DNA mismatch repair heterogeneous tumors promotes immune surveillance.
  Cancer Cell. 2023 Jan 9;41(1):196-209.
• Pergolizzi M, Bizzozero L, Maione F, Maldi E, Isella C, Macagno M, Mariella E, Bardelli A, Medico E, Marchiò C, Serini G, Di Nicolantonio F, Bussolino F, Arese M.
  The neuronal protein Neuroligin 1 promotes colorectal cancer progression by modulating the APC/β-catenin pathway.
  J Exp Clin Cancer Res. 2022 Sep 2;41(1):266.
• Durinikova E, Reilly NM, Buzo K, Mariella E, Chilà R, Lorenzato A, Dias JML, Grasso G, Pisati F, Lamba S, Corti G, Degasperi A, Cancelliere C, Mauri G, Andrei P, Linnebacher M, Marsoni S, Siena S, Sartore-Bianchi A, Nik-Zainal S, Di Nicolantonio F, Bardelli A*, Arena S* (* Shared last authorship)
  Targeting the DNA Damage Response Pathways and Replication Stress in Colorectal Cancer.
  Clin Cancer Res. 2022 Sep 1;28(17):3874-3889.
• Sartore-Bianchi A, Pietrantonio F, Lonardi S, Mussolin B, Rua F, Crisafulli G, Bartolini A, Fenocchio E, Amatu A, Manca P, Bergamo F, Tosi F, Mauri G, Ambrosini M, Daniel F, Torri V, Vanzulli A, Regge D, Cappello G, Marchiò C, Berrino E, Sapino A, Marsoni S, Siena S, Bardelli A.
  Circulating tumor DNA to guide rechallenge with panitumumab in metastatic colorectal cancer: the phase 2 CHRONOS trial.
  Nat Med. 2022 Aug;28(8):1612-1618.
• Russo M, Pompei S, Sogari A, Corigliano M, Crisafulli G, Puliafito A, Lamba S, Erriquez J, Bertotti A, Gherardi M, Di Nicolantonio F, Bardelli A, Cosentino Lagomarsino M.
  A modified fluctuation-test framework characterizes the population dynamics and mutation rate of colorectal cancer persister cells.
  Nat Genet. 2022 Jul;54(7):976-984.
• Mauri G, Vitiello PP, Sogari A, Crisafulli G, Sartore-Bianchi A, Marsoni S, Siena S, Bardelli A.
  Liquid biopsies to monitor and direct cancer treatment in colorectal cancer.
  Br J Cancer. 2022 Aug;127(3):394-407