Cancer can be suppressed by alkalizing the tumor microenvironment: the effectiveness of “alkalization therapy” in cancer treatment

Introduction

Specific somatic mutations have long been recognized to transform normal cells into cancerous cells, primarily through activating proto-oncogenes and inducing the loss of function of genes [1]. However, the direct role of somatic mutations in carcinogenesis [2] and the process by which normal cells become cancerous are still areas of ongoing research.

Otto Warburg, a pioneer in cancer metabolism, first reported that cancer cells undergo abnormal metabolism. Warburg identified that, unlike normal cells, which mainly generate energy through oxidative phosphorylation, cancer cells rely substantially on substrate-level phosphorylation and glycolysis [3], 4]. This characteristic, known as the Warburg effect, has been shown to play an essential role in the treatment resistance of cancer cells [5], 6]. Warburg effect was referenced in an intriguing study by Goldblatt and Cameron, who demonstrated that rat myocardial fibroblasts exposed to intermittent anaerobic conditions undergo tumorigenic changes [7].

Through the above processes, the metabolism of cancer cells deviates from typical metabolic regulation, which then promotes aerobic glycolysis. The activation of this “glycolytic switch” is a crucial factor that promotes tumorigenesis and is observed in approximately 70–80 % of human cancers [8]. This metabolic reprogramming, driven by factors such as hypoxia-inducible factor-1 overexpression, oncogene activation (e.g., cMyc, Ras), and the loss of tumor suppressor genes (e.g., p53, PTEN), is a hallmark of cancer [8].

The tumor microenvironment (TME), which comprises stromal cells, including fibroblasts, macrophages, and lymphocytes, surrounds the tumor mass and forms the tumor stroma. In the TME, factors such as hypoxia, low pH, and low glucose concentration promote tumor growth [9], 10]. The excess protons generated by aerobic glycolysis are expelled from the cancer cell by pumps, such as sodium-hydrogen exchanger isoform 1 (NHE-1), creating a highly acidic microenvironment around the cancer cells [10], 11]. Whereas the intracellular pH (pHi) of normal cells is neutral (ranging from 6.9 to 7.1), the pHi of cancer cells tends to be alkaline (between 7.2 and 7.7) [12], 13]. The protons in the acidic TME recruit bone marrow-derived suppressor cells, resulting in a substantial increase in inflammatory cells, such as neutrophils and macrophages [14], [15], [16], [17], [18].

The acidified TME substantially affects tumor progression, and leads to the following characteristics [19], [20], [21], [22], [23]:

1. Increased malignancy;

2. Increased activation of cell proliferation and division cycles;

3. Expression and activation of genetic abnormalities and oncogenes;

4. Activation of cell proliferation factors;

5. Increased glycolytic activity;

6. Activation of DNA synthesis;

7. Activation of cell migration;

8. Stimulation of angiogenesis;

9. Increased metastatic potential;

10. Activation of multidrug resistance genes.

A strong association between increased pHi and the acquisition of multidrug resistance (MDR) has also been established [10], highlighting the importance of pH in cancer treatment. It has been shown in human lung cancer cells that an increase in pHi from 7.0 to 7.4 enhances resistance to adriamycin by approximately 2,000-fold [24]. The drug tended to accumulate in cells with acidic pHi, while conversely, it decreased its accumulation in cells with alkaline pHi.

As a result, cancer cells adapt to the acidified TME, acquiring more aggressive and drug-resistant characteristics.

These findings suggest that promoting intracellular acidification in cancer cells is essential for overcoming MDR, and for establishing more effective treatment strategies. Targeting membrane-bound transporters, such as NHE-1 and H⁺/ATPase to induce intracellular acidification presents a promising therapeutic approach. Indeed, angiogenesis inhibitors have been found to suppress the activity of NHE-1 and H⁺/ATPase, thereby promoting the intracellular acidification of cancer cells [10], 11], 25].

The concept of “alkalization therapy” has gained attention as a method for alkalizing the extracellular environment, which subsequently induces intracellular acidification by reducing the activity of NHE-1 and H⁺/ATPase. Through “alkalization therapy,” we aim to modify the extracellular environment of cancer cells via dietary alkalization by the intake of bicarbonate or citrate salts, aiming to maintain a urine pH of 7.5 or higher [12]. In mouse cancer models, bicarbonate intake has been shown to increase extracellular pH, resulting in the reduced metastatic potential of cancer cells and tumor size [26], 27]. These findings suggest that alkalization therapy can enhance the efficacy of existing cancer treatments [24], 28].

Alkalization therapy focuses on foods that promote alkalization. It is important to minimize the intake of meat and processed foods to reduce acid load and support a systemic alkaline environment [29]. Our research group has shown that improving patients’ body constitution and changing the TME to an alkaline state can improve the efficacy of cancer treatment [30]. However, no previous studies have analyzed the long-term prognosis of cancer patients who undergo alkalization therapy. Hence, this study aims to analyze the 5-year survival rate of cancer patients undergoing alkalization therapy and to clarify the differences according to their urine pH levels.

Analysis methods

Study design

This study was a retrospective analysis conducted to evaluate the 5-year survival rates and the long-term potential effects of alkalization therapy on patients with stage IV metastatic cancers. The analysis was conducted on 1,110 cases of patients with stage IV cancers who first visited the Karasuma Wada Clinic between January 2014 and December 2023 (Figure 1). The observation period extended from the first visit until April 30, 2024, during which patients continued to visit the clinic. Among them, there were 127 patients with stage Ⅳ pancreatic cancer, 131 patients with stage Ⅳ breast cancer, 253 patients with stage Ⅳ non-small cell lung cancer (NSCLC), and 599 patients with other stage IV cancers. The average urine pH of each patient was measured from the first visit to the last visit. Patients who survived more than 10 days from the initial visit, visited the clinic at least 3 times, and provided urine samples on each visit were included in the study. Data was gathered from the clinic’s medical records. All patients received alkalization therapy, which included an alkalizing diet and the oral administration of alkalizing agents, such as sodium bicarbonate and citric acid. The patients attended at least three outpatient visits and followed the alkalization therapy protocol outlined below. During each visit, patients received instruction on the specifics of the alkalization therapy. Based on the authors’ previous finding that an increase in pH by at least 1 unit is associated with improved prognosis [31], the patients were divided into three urine pH groups, namely, pH 5.5 or less (Group 1), more than pH 5.5 but less than 7.5 (Group 2), and pH 7.5 or more (Group 3), and their 5-year survival rates were analyzed.

Figure 1:

Flow chart for patient inclusion and exclusion.

The study was conducted in accordance with the Declaration of Helsinki, approved by the Institutional Review Board of the Japan Chapter of the American College of Chest Physicians (approval number 2023-1), and has been registered with UMIN Clinical Trials under registration number UMIN000052333 (date of the registration, 21 September 2023).

The analysis was conducted on 1,110 cases of patients with stage IV cancers who first visited the Karasuma Wada Clinic between January 2014 and December 2023. The observation period extended from the first visit until April 30, 2024, during which patients continued to visit the clinic. Patients with 3 cancer types (pancreatic, breast, and non-small cell lung cancer) were analyzed.

Results

The 5-year survival rates of patients with stage Ⅳ cancers were analyzed. As shown in Table 1 and Figure 2A, there were 1,110 patients with stage Ⅳ cancer at Wada Clinic, and the 5-year survival rate was 37.7 %, while it was 15.7 % of 109,308 patients in the report from the National Cancer Center of Japan.

Figure 2:

Kaplan-Meier survival curve for the Wada Clinic recorded 1,110 patients with stage Ⅳ cancer of various types. (A) Shows the 5-year survival rate for all cancers at stage IV of 37.7 %. The National Cancer Center Japan reported a 5-year survival rate of 15.7 %. The inserted table shows the multivariate survival analysis using the Cox proportional hazards model. The solid line in the graph represents the point estimate of the survival rate, and the dashed lines indicate the 95 % confidence interval. (B) Shows the 5-year survival rates of patients with stage IV cancers categorized by urine pH levels as follows: Group 1 (pH≥7.5), Group 2 (5.5<pH<7.5), and Group 3 (pH≤5.5). Groups 1 and 2 demonstrated higher survival rates than Group 3.

On multivariate survival analysis using the Cox proportional hazards model, in which urine pH, sex, and age at first visit were included as explanatory variables, high urine pH was the only statistically significant prognostic factor, with a hazard ratio (HR) of 0.68 (95 % confidence interval (CI): 0.58–0.80, p<0.0001), indicating that a 1-unit increase in urine pH corresponds to a 32 % reduction in the risk of death. It is important to note that the analysis does not specify a particular qualification or range for urine pH. Most patients at Wada Clinic have been diagnosed as having stage IV cancer, and most of these individuals have been referred to our clinic for palliative care after having undergone all standard cancer treatments.

As shown in Figure 2B, the association between urine pH and survival rate for patients with all types of stage Ⅳ cancer was analyzed. In the 51 patients in Group 3 (pH≤5.5), the 5-year survival rate had not yet been reached at the time of the analysis. The 5-year survival rate for the 737 patients in Group 2 (5.5<pH<7.5) was 38.0 %, and for the 322 patients in Group 1 (pH≥7.5) was 38.5 %. The log-rank test showed a significant difference between urine pH levels among the 3 groups (p<0.0001). Additionally, when the analysis was performed using a urine pH cutoff point of 5.5 (≤5.5 vs. >5.5), a significant difference in overall survival was observed between the 2 groups (p<0.0001). When the analysis was performed using a urine pH cutoff point of 5.5 (≤5.5 vs. >5.5), a significant difference in overall survival was observed between the 2 groups (p<0.0001).

The 5-year survival rate for patients with stage Ⅳ pancreatic cancer was 7.9 %, as shown in Figure 3A. It is well known that the prognosis of stage Ⅳ pancreatic cancer patients is extremely unfavorable [31], 34]. Indeed, the National Cancer Center of Japan reported a 5-year survival rate of 1.8 %. On multivariate survival analysis using the Cox proportional hazards model, in which urine pH, sex, and age at first visit were included as explanatory variables, urine pH was the only statistically significant prognostic factor, with an HR of 0.55 (95 % CI: 0.36–0.83, p=0.004), indicating that a 1-unit increase in urine pH corresponds to a 45 % reduction in the risk of death, confirming that a higher urine pH is associated with improved survival. It is important to note that the analysis does not provide a specific qualification or range for urine pH. Figure 3B shows the 5-year survival rates for patients with stage Ⅳ pancreatic cancer, categorized by urine pH levels. There were 10 patients in Group 3 (pH≤5.5), and all individuals either died or discontinued their visits by day 122. There were 93 patients in Group 2 (5.5<pH<7.5), and the 5-year survival rate for this group was 8.1 %. There were 24 patients in Group 1 (pH≥7.5), and the 5-year survival rate was 9.6 %. The log-rank test demonstrated a significant difference in survival rates among the 3 groups (p<0.0001). Additionally, when the analysis was performed using a urine pH cutoff point of 5.5 (≤5.5 vs. >5.5), a significant difference in overall survival was observed between the 2 groups (p<0.0001).

Figure 3:

Kaplan-Meier survival curve for the Wada Clinic recorded 127 patients with stage Ⅳ pancreatic cancer. (A) Shows the 5-year survival rate for stage IV pancreatic cancer of 7.9 %. The National Cancer Center of Japan reported a 5-year survival rate of 1.8 %. The solid line in the graph represents the point estimate of the survival rate, and the dashed lines indicate the 95 % confidence interval. The inserted table shows the multivariate survival analysis using the Cox proportional hazards model. (B) Shows the 5-year survival rates of patients with stage IV pancreatic cancer, categorized by urine pH levels as follows: Group 1 (pH≥7.5), Group 2 (5.5<pH<7.5), and Group 3 (pH≤5.5). The log-rank test showed a significant difference between the 3 groups. Group 3 with a urine pH≤5.5 and the other 2 groups. Additionally, when the analysis was performed using a urine pH cutoff point of 5.5 (≤5.5 vs. >5.5), a significant difference in overall survival was observed between the 2 groups (p<0.0001).

Figure 4A shows the 5-year survival rate for patients with stage IV breast cancer. Whereas this was reported to be 39.3 % by the National Cancer Center of Japan, it was 44.3 % for the 131 patients at Wada Clinic. Multivariate analysis using the Cox proportional hazards model, in which urine pH, sex, and age at first visit were included as explanatory variables, demonstrated that none of these variables significantly correlated with survival. Figure 4B shows the 5-year survival rates for patients with stage Ⅳ breast cancer, categorized by their urine pH levels. In Group 3 (pH≤5.5), all individuals either died or discontinued their visits by 893 days after their first visit. Group 2 (5.5<pH<7.5) included 74 patients, and the 5-year survival rate was 55.6 %. Group 1 (pH≥7.5) included 52 patients, and the 5-year survival rate was 38.9 %. The log-rank test demonstrated a significant difference in survival rates among the 3 groups (p=0.009). Additionally, when the analysis was performed using a urine pH cutoff point of 5.5 (≤5.5 vs. >5.5), a significant difference in overall survival was observed between the 2 groups (p=0.0032).

Figure 4:

Kaplan-Meier survival curve for the Wada Clinic recorded 131 patients with stage Ⅳ breast cancer. (A) Shows the 5-year survival rate of 44.3 %. The National Cancer Center of Japan reported a 5-year survival rate of 39.3 %. The inserted table shows that the multivariate survival analysis did not identify urine pH as a statistically significant prognostic factor. The solid line in the graph represents the point estimate of the survival rate, and the dashed lines indicate the 95 % confidence interval. (B) Shows 5-year survival rates of patients with stage IV breast cancer, categorized by urine pH levels as follows: Group 1 (pH≥7.5), Group 2 (5.5<pH<7.5), and Group 3 (pH≤5.5). Group 1 (urine pH≥7.5) demonstrated the highest survival rate.

The 5-year survival rate for patients with stage Ⅳ NSCLC is shown in Figure 5A. There were 253 patients with stage Ⅳ NSCLC at Wada Clinic during the study period, and the 5-year survival rate was 48.6 %. On the other hand, the 5-year survival rate at the National Cancer Center of Japan was 6.4 %. Multivariate analysis using the Cox proportional hazards model, in which urine pH, sex, and age at first visit were included as explanatory variables, demonstrated that none of these variables significantly correlated with survival. Figure 5B shows the 5-year survival rates of stage Ⅳ NSCLC patients stratified into 3 groups according to their urine pH level. Group 3 (pH≤5.5) included 9 patients, and on the 670th day, 1 patient died, and the estimated 5-year survival rate became 0 %. Group 2 (5.5<pH<7.5) included 171 patients, and the 5-year survival rate was 51.9 %. Group 1 (pH≥7.5) included 73 patients, and the 5-year survival rate was 41.6 %. There were no significant differences in survival rates among the 3 groups (p=0.13). However, when the analysis was performed using a urine pH cutoff point of 5.5 (≤5.5 vs. >5.5), a significant difference in overall survival was observed between the 2 groups (p=0.0434), suggesting that higher urine pH levels are associated with a more favorable prognosis.

Figure 5:

Kaplan-Meier survival curve for the Wada Clinic recorded 253 patients with stage Ⅳ non-small cell lung cancer (NSCLC). (A) Shows a 5-year survival rate of 48.6 %. The National Cancer Center of Japan reported a 5-year survival rate of 6.4 %. The inserted table shows that the multivariate survival analysis did not identify urine pH as a statistically significant prognostic factor. The solid line in the graph represents the point estimate of the survival rate, and the dashed lines indicate the 95 % confidence interval. (B) Shows the 5-year survival rates for patients with stage IV NSCLC, categorized by urine pH levels as follows: Group 1 (pH≥7.5), Group 2 (5.5<pH<7.5), and Group 3 (pH≤5.5).

Discussion

Conclusions

This study analyzes the long-term prognosis of cancer patients undergoing alkalization therapy. Our results suggest that urinary pH may be a prognostic indicator for certain types of cancer. In pancreatic cancer, a multivariate survival analysis showed that urinary pH is a statistically significant prognostic factor. For breast cancer patients, categorizing patients by three different urine pH levels revealed significant differences in survival rates. In patients with NSCLC, a cut-off level of pH 5.5 also showed a significant difference in outcomes. However, a key challenge remains in developing an effective method to measure the pH of the TME and establishing a correlation between the alkalization of urine and that of the TME.

We acknowledge several limitations of this study. This investigation was a single-center, retrospective analysis focused on evaluating the safety and efficacy of alkalization therapy. Nonetheless, genetic mutations and concomitant chemotherapy were not adjusted as confounding factors, which renders their associations ambiguous. Moreover, the impact of combination therapies – such as chemotherapy, molecular-targeted therapy, and immunotherapy – on clinical outcomes were not controlled for. Conducting stratified or subgroup analyses could enhance the interpretability of the results. Additionally, while information regarding prior treatments at other institutions was accessible at the time of the initial consultation, data concerning treatments administered after the first visit outside the Wada clinic were collected only partially. Regular and comprehensive follow-up on these variables may be crucial for a more precise assessment of treatment outcomes. Finally, although the findings are promising, the single-institution, non-randomized study design inherently limits the external validity. Future validation through randomized controlled trials or well-structured matched cohort studies will be necessary to substantiate these observations.

Although the mechanism underlying the varying effectiveness of alkalization therapy among different cancer types is not yet fully understood, and the sample size was limited in this study, using urine pH as an indicator for systemic acid-base balance holds promise for enhancing cancer treatment effectiveness and improving patient compliance, as it is a simple and noninvasive test. Further research is needed to investigate the full potential of alkalization therapy and its underlying mechanisms.