Ablating all three retinoblastoma family members in mouse lung leads to neuroendocrine tumor formation

Abstract

Lung cancer is a deadly disease with increasing cases diagnosed worldwide and still a very poor prognosis. While mutations in the retinoblastoma (RB1) tumor suppressor have been reported in lung cancer, mainly in small cell lung carcinoma, the tumor suppressive role of its relatives p107 and p130 is still a matter of debate. To begin to investigate the role of these two Rb family proteins in lung tumorigenesis, we have generated a conditional triple knockout mouse model (TKO) in which the three Rb family members can be inactivated in adult mice. We found that ablation of all three family members in the lung of mice induces tumorlets, benign neuroendocrine tumors that are remarkably similar to their human counterparts. Upon chemical carcinogenesis, DHPN and urethane accelerate tumor development; the TKO model displays increased sensitivity to DHPN, and urethane increases malignancy of tumors. All the tumors developing in TKO mice (spontaneous and chemically induced) have neuroendocrine features but do not progress to fully malignant tumors. Thus, loss of Rb and its family members confers partial tumor susceptibility in neuroendocrine lineages in the lungs of mice. Our data also imply the requirement of other oncogenic signaling pathways to achieve full transformation in neuroendocrine lung lesions mutant for the Rb family.

Differential development of large-cell neuroendocrine or small-cell lung carcinoma upon inactivation of 4 tumor suppressor genes

“…Adeno-cre intratracheal infection has proven to be a robust method of modeling lung cancer in mice (16). We used 2 different approaches: on the one hand we used conventional cytomegalovirus promoter, Ad5-CMVcre, which targets most lung cell types (17) ( SI Appendix , Fig. S1 A – E ); on the other hand, we used an adenovirus (Ad5-K5cre) in which cre recombinase is under the control of keratin K5 promoter (18).…”

“…Additional Rbl1 loss renders LCNEC as the predominant tumor type in our CMV-QKO mice (Ad5-CMVcre) and SCLC in our K5-QKO mice (Ad5-K5cre), illustrating that both genetic alterations and characteristics of the initiated cells orchestrate the evolution of tumor phenotype (33). The fact that neuroendocrine tumors arise almost exclusively in both CMV-QKO and K5-QKO models highlights the ability of this gene to drive tumors to neuroendocrine phenotype (17). The extended animal survival of 17.5 wk in the Ad5-CMVcre Cui et al model (25) versus 11 wk in the current CMV-QKO model shows that the additional loss of Rbl1 accelerates tumor onset and supports a role for this gene as a tumor suppressor in lung cancer, as previously described in epidermal tumors (13–15).…”

Neuroendocrine Lung Cancer Mouse Models: An Overview

“…This could be explained at least in part because most of the carcinogens, for which the mechanism of action is known, induce the activation of oncogenes such as K-ras [40][41][42], while the combinations of Trp53 and Rb alterations, responsible for the development of high-grade neuroendocrine tumors, are almost never found. Nevertheless, when applied to Rb-family deficient GEMMs, chemical carcinogens induce exclusively neuroendocrine tumors [21].…”

“…However, the characteristics of the primary tumors originating from this cell line are not consistent with the biology of a typical carcinoid, thus hampering the understanding of the molecular mechanisms underlying this tumor type. Chemically induced GEMMs for TC and AC exist: a triple knockout mutant model in which all the three Rb family members are ablated develops TC after DHPN (N-bis(2-hydroxypropyl) nitrosamine, a potent mutagen and a wide-spectrum carcinogen in rodents) administration and AC after urethane (an inducer of K-ras activation) treatment [21].…”

Development and long-term evaluation of a new 68Ge/68Ga generator based on nano-SnO2 for PET imaging

“…All animal experiments were approved by the Animal Ethical Committee of the Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT) and conducted in compliance with institutional and national guidelines. A mouse model of high-grade neuroendocrine lung cancer (LCNEC) based on the ablation of four tumor suppressor genes (Rb, Rbl1,pTEN and Trp53) was used to perform imaging studies 33 , 34 , 38 .…”