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Role of p53 and p16 gene alterations in determining response to concurrent paclitaxel and radiation in solid tumor
T C King1, O C Estalilla, H Safran
1Departments of Pathology and Laboratory Medicine, Lifespan, Providence, RI, USA.
Abstract:
Molecular genetic alterations that disturb cell cycle regulation in tumor cells can affect their response to chemotherapeutic agents and radiation. Many genes that regulate the critical cell cycle checkpoint at G1S are altered in human tumors. These genetic changes can result in uncontrolled cellular proliferation, genetic instability, and altered response to radiation and chemotherapy. The p53 tumor suppressor gene serves a critical role at the G1S transition, where it can either block entry into S phase or activate programmed cell death (apoptosis) in response to DNA damage. p53 Gene mutations are common in human tumors and interfere with the activation of apoptosis in response to most chemotherapeutic agents. Paclitaxel is a potent chemotherapeutic agent that interferes with mitotic spindle function to block cells at G2M, the most radiosensitive phase of the cell cycle. Utilization of paclitaxel as a radiation sensitizer in vivo to treat aggressive, locally advanced neoplasms has resulted in high response rates and acceptable toxicity in protocols for non-small cell lung carcinoma, upper gastrointestinal tract carcinoma, and other malignancies. Recent evidence suggests that paclitaxel is unique in its ability to activate apoptosis in tumor cells with p53 mutations in vitro and in vivo. The p16(INK4a) (MTS-1, CDKN2) gene product acts in the same pathway as p53 to inhibit cell cycle progression at G1/S. p16(INK4a) is deleted and/or mutated in a significant fraction of human tumors, including pancreatic carcinoma. The effects of p16(INK4a) alterations in response to paclitaxel/radiation and the risk of systemic relapse are currently being evaluated. Information about molecular genetic alterations in individual tumors ultimately may be a critical factor in choosing between therapeutic options.
Insights
Paclitaxel shows promise in sensitizing tumors to radiation, even those with p53 mutations. This chemotherapy agent may overcome genetic alterations that hinder cancer cell death, offering new therapeutic strategies.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Genetics
Background:
- Molecular genetic alterations in cell cycle regulation impact cancer treatment response.
- Key cell cycle checkpoints, like G1S, are frequently disrupted in tumors, leading to uncontrolled proliferation and altered sensitivity to therapies.
- The p53 tumor suppressor gene is crucial for G1S transition and apoptosis induction, with mutations common in cancers, often impairing responses to chemotherapy.
Purpose of the Study:
- To investigate the role of molecular genetic alterations in cancer cell cycle regulation and their influence on treatment outcomes.
- To evaluate paclitaxel's efficacy as a radiation sensitizer, particularly in tumors with p53 mutations.
- To explore the impact of p16(INK4a) alterations on response to paclitaxel/radiation therapy.
Main Methods:
- Review of existing evidence on molecular genetic alterations affecting cell cycle checkpoints.
- Analysis of paclitaxel's mechanism of action, focusing on its effects at the G2M phase and radiosensitivity.
- Examination of studies investigating paclitaxel's ability to induce apoptosis in p53-mutated cancer cells.
- Consideration of the role of p16(INK4a) gene alterations in pancreatic carcinoma and other tumors.
Main Results:
- Paclitaxel effectively sensitizes cells to radiation by arresting them at the radiosensitive G2M phase.
- Evidence suggests paclitaxel uniquely induces apoptosis in tumor cells with p53 mutations, both in vitro and in vivo.
- Paclitaxel has demonstrated high response rates and acceptable toxicity in treating advanced solid tumors when used as a radiation sensitizer.
Conclusions:
- Molecular genetic alterations, particularly in cell cycle regulators like p53 and p16(INK4a), significantly influence cancer treatment efficacy.
- Paclitaxel represents a promising therapeutic agent for enhancing radiation sensitivity, especially in cancers with compromised p53 function.
- Personalized therapeutic strategies based on individual tumor molecular profiles may become critical for optimizing cancer treatment selection.