STAT3 Sustains Tumorigenicity Following Mutant KRAS Ablation

Area of Science:

• Oncology
• Molecular Biology
• Immunology

Background:

• Oncogenic KRAS mutations are drivers of aggressive cancers, but their inactivation alone is insufficient for tumor control.
• Pancreatic ductal adenocarcinoma (PDAC) presents a significant challenge due to tumor persistence after KRAS inhibition.
• STAT3 has been implicated in maintaining cancer stemness and immune evasion, crucial for tumor survival.

Purpose of the Study:

• To investigate the role of STAT3 in maintaining malignant identity in KRAS-mutated cancers.
• To determine if combined inactivation of KRAS and STAT3 can lead to tumor regression.
• To elucidate the mechanisms by which STAT3 contributes to cancer persistence after KRAS inactivation.

Main Methods:

• CRISPR-mediated gene editing to ablate mutant KRAS and STAT3 in a PDAC model.
• Assessment of tumor progression, malignant identity, and immune rejection in vivo.
• Analysis of core transcriptional programs affected by combined KRAS and STAT3 loss.

Main Results:

• CRISPR-mediated ablation of mutant KRAS terminated tumor progression only when STAT3 was concomitantly inactivated.
• Combined KRAS and STAT3 loss disrupted a critical cancer cell transcriptional program, impairing tumor growth in mice.
• Tumor cells lacking both KRAS and STAT3 exhibited enhanced immune rejection, leading to tumor clearance.

Conclusions:

• STAT3 acts as a critical enforcer of oncogenic identity in KRAS-ablated tumors, rather than solely providing transformation features.
• The combined inactivation of KRAS and STAT3 disrupts essential cancer cell programs, leading to loss of malignant identity.
• This study reveals a vulnerability in KRAS-driven cancers, suggesting STAT3 as a target for combination therapies to achieve durable tumor control.